Set up a new device to test V1 applications on V2 (Greengrass nucleus lite)

import greengrasssdk
import json

iot_client = greengrasssdk.client('iot-data')

def lambda_handler(event, context):
    """
    Receives temperature from publisher Lambda,
    processes it, and forwards to subscriber Lambda
    """
    # Receive from publisher Lambda.
    sensor_id = event['sensor_id']
    temperature = event['temperature']
    
    print(f"Received from sensor {sensor_id}: {temperature}°F")
    
    # Process: Check if temperature is high.
    if temperature > 80:
        alert_data = {
            'sensor_id': sensor_id,
            'temperature': temperature,
            'alert': 'HIGH_TEMPERATURE'
        }
        
        # Publish to another Lambda using greengrasssdk.
        iot_client.publish(
            topic='lambda/alerts',
            payload=json.dumps(alert_data)
        )
        
        print(f"Alert sent to subscriber Lambda")
    
    return {'statusCode': 200}

import com.amazonaws.greengrass.javasdk.IotDataClient;
import com.amazonaws.greengrass.javasdk.model.PublishRequest;
import com.amazonaws.services.lambda.runtime.Context;
import com.google.gson.Gson;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;

public class TemperatureProcessorLambda {
    private static final Gson gson = new Gson();
    private final IotDataClient iotDataClient;

    public TemperatureProcessorLambda() {
        this.iotDataClient = new IotDataClient();
    }

    public String handleRequest(Map<String, Object> event, Context context) {
        /*
         * Receives temperature from publisher Lambda,
         * processes it, and forwards to subscriber Lambda
         */

        // Receive from publisher Lambda.
        String sensorId = (String) event.get("sensor_id");
        Number temp = (Number) event.get("temperature");
        int temperature = temp.intValue();

        System.out.println("Received from sensor " + sensorId + ": " + temperature + "°F");

        // Process: Check if temperature is high.
        if (temperature > 80) {
            Map<String, Object> alertData = new HashMap<>();
            alertData.put("sensor_id", sensorId);
            alertData.put("temperature", temperature);
            alertData.put("alert", "HIGH_TEMPERATURE");

            // Publish to another Lambda using greengrasssdk.
            String payload = gson.toJson(alertData);
            PublishRequest publishRequest = new PublishRequest()
                .withTopic("lambda/alerts")
                .withPayload(ByteBuffer.wrap(payload.getBytes(StandardCharsets.UTF_8)));

            iotDataClient.publish(publishRequest);

            System.out.println("Alert sent to subscriber Lambda");
        }

        return "Success";
    }
}

const greengrasssdk = require('aws-greengrass-core-sdk');

const iotClient = new greengrasssdk.IotData();

/**
 * Greengrass v1 Lambda function
 * Receives temperature from publisher Lambda,
 * processes it, and forwards to subscriber Lambda
 */
exports.handler = function(event, context) {
    // Receive from publisher Lambda.
    const sensorId = event.sensor_id;
    const temperature = event.temperature;
    
    console.log(`Received from sensor ${sensorId}: ${temperature}°F`);
    
    // Process: Check if temperature is high.
    if (temperature > 80) {
        const alertData = {
            sensor_id: sensorId,
            temperature: temperature,
            alert: 'HIGH_TEMPERATURE'
        };
        
        // Publish to another Lambda using greengrasssdk.
        const params = {
            topic: 'lambda/alerts',
            payload: JSON.stringify(alertData)
        };
        
        iotClient.publish(params, (err) => {
            if (err) {
                console.error('Error publishing alert:', err);
                context.fail(err);
            } else {
                console.log('Alert sent to subscriber Lambda');
                context.succeed('Success');
            }
        });
    } else {
        context.succeed('Success');
    }
};

#include <aws/greengrass/greengrasssdk.h>
#include <stdio.h>
#include <string.h>
#include <jansson.h>  // For JSON parsing.

static aws_greengrass_iot_data_client *iot_client = NULL;

void on_message_received(const char *topic, const uint8_t *payload, size_t payload_len, void *user_data) {
    // Parse the incoming message.
    char *payload_str = strndup((char *)payload, payload_len);
    json_error_t error;
    json_t *event = json_loads(payload_str, 0, &error);
    free(payload_str);
    
    if (!event) {
        fprintf(stderr, "Error parsing JSON: %s\n", error.text);
        return;
    }
    
    // Receive from publisher Lambda.
    json_t *sensor_id_obj = json_object_get(event, "sensor_id");
    json_t *temperature_obj = json_object_get(event, "temperature");
    
    const char *sensor_id = json_string_value(sensor_id_obj);
    int temperature = json_integer_value(temperature_obj);
    
    printf("Received from sensor %s: %d°F\n", sensor_id, temperature);
    
    // Process: Check if temperature is high.
    if (temperature > 80) {
        // Create alert data.
        json_t *alert_data = json_object();
        json_object_set_new(alert_data, "sensor_id", json_string(sensor_id));
        json_object_set_new(alert_data, "temperature", json_integer(temperature));
        json_object_set_new(alert_data, "alert", json_string("HIGH_TEMPERATURE"));
        
        // Convert to JSON string.
        char *alert_payload = json_dumps(alert_data, JSON_COMPACT);
        
        // Publish to another Lambda using greengrasssdk.
        aws_greengrass_publish_params params = {
            .topic = "lambda/alerts",
            .payload = (uint8_t *)alert_payload,
            .payload_len = strlen(alert_payload)
        };
        
        aws_greengrass_iot_data_publish(iot_client, &params);
        
        printf("Alert sent to subscriber Lambda\n");
        
        free(alert_payload);
        json_decref(alert_data);
    }
    
    json_decref(event);
}

int main(int argc, char *argv[]) {
    // Initialize Greengrass SDK.
    iot_client = aws_greengrass_iot_data_client_new();
    
    // Subscribe to temperature sensor topic.
    aws_greengrass_subscribe_params subscribe_params = {
        .topic = "sensors/temperature",
        .callback = on_message_received,
        .user_data = NULL
    };
    
    aws_greengrass_iot_data_subscribe(iot_client, &subscribe_params);
    
    printf("Temperature Processor Lambda started\n");
    printf("Subscribed to sensors/temperature\n");
    printf("Waiting for sensor data...\n");
    
    // Keep the Lambda running.
    while (1) {
        sleep(1);
    }
    
    return 0;
}

#include <aws/greengrass/greengrasssdk.h>
#include <iostream>
#include <string>
#include <memory>
#include <jansson.h> // For JSON parsing.
#include <unistd.h>

class TemperatureProcessor {
private:
    std::unique_ptr<aws_greengrass_iot_data_client, 
                    decltype(&aws_greengrass_iot_data_client_destroy)> iot_client;
    
    static void message_callback_wrapper(const char *topic, 
                                        const uint8_t *payload, 
                                        size_t payload_len, 
                                        void *user_data) {
        auto* processor = static_cast<TemperatureProcessor*>(user_data);
        processor->on_message_received(topic, payload, payload_len);
    }

public:
    TemperatureProcessor() 
        : iot_client(aws_greengrass_iot_data_client_new(), 
                     aws_greengrass_iot_data_client_destroy) {
        if (!iot_client) {
            throw std::runtime_error("Failed to create Greengrass IoT client");
        }
    }

    void on_message_received(const char *topic, 
                            const uint8_t *payload, 
                            size_t payload_len) {
        // Parse the incoming message.
        std::string payload_str(reinterpret_cast<const char*>(payload), payload_len);
        
        json_error_t error;
        json_t *event = json_loads(payload_str.c_str(), 0, &error);
        
        if (!event) {
            std::cerr << "Error parsing JSON: " << error.text << std::endl;
            return;
        }

        json_t *sensor_id_obj = json_object_get(event, "sensor_id");
        json_t *temperature_obj = json_object_get(event, "temperature");
        
        const char *sensor_id = json_string_value(sensor_id_obj);
        int temperature = json_integer_value(temperature_obj);
        
        std::cout << "Received from sensor " << sensor_id 
                  << ": " << temperature << "°F" << std::endl;

        if (temperature > 80) {
            send_alert(sensor_id, temperature);
        }

        json_decref(event);
    }

    void send_alert(const char *sensor_id, int temperature) {
        // Create alert data.
        json_t *alert_data = json_object();
        json_object_set_new(alert_data, "sensor_id", json_string(sensor_id));
        json_object_set_new(alert_data, "temperature", json_integer(temperature));
        json_object_set_new(alert_data, "alert", json_string("HIGH_TEMPERATURE"));

        // Convert to JSON string.
        char *alert_payload = json_dumps(alert_data, JSON_COMPACT);

        // Publish to another Lambda using greengrasssdk.
        aws_greengrass_publish_params params = {
            .topic = "lambda/alerts",
            .payload = reinterpret_cast<uint8_t*>(alert_payload),
            .payload_len = strlen(alert_payload)
        };
        
        aws_greengrass_iot_data_publish(iot_client.get(), &params);
        
        std::cout << "Alert sent to subscriber Lambda" << std::endl;

        free(alert_payload);
        json_decref(alert_data);
    }

    void subscribe_to_topic(const std::string& topic) {
        aws_greengrass_subscribe_params subscribe_params = {
            .topic = topic.c_str(),
            .callback = message_callback_wrapper,
            .user_data = this
        };
        
        aws_greengrass_iot_data_subscribe(iot_client.get(), &subscribe_params);
        
        std::cout << "Temperature Processor Lambda started" << std::endl;
        std::cout << "Subscribed to " << topic << std::endl;
        std::cout << "Waiting for sensor data..." << std::endl;
    }

    void run() {
        // Keep the Lambda running.
        while (true) {
            sleep(1);
        }
    }
};

int main(int argc, char *argv[]) {
    try {
        TemperatureProcessor processor;
        processor.subscribe_to_topic("sensors/temperature");
        processor.run();
    } catch (const std::exception& e) {
        std::cerr << "Error: " << e.what() << std::endl;
        return 1;
    }
    
    return 0;
}

Prerequisites: Before using this component code, install and verify the Amazon IoT Device SDK for Python on your Greengrass device:

# Install the SDK
pip3 install awsiotsdk

# Verify installation
python3 -c "import awsiot.greengrasscoreipc.clientv2; print('SDK installed successfully')"

If you encounter dependency conflicts during installation, try installing a specific version of the Amazon IoT Device SDK.

If the verification command prints "SDK installed successfully", you're ready to use the component code:

from awsiot.greengrasscoreipc.clientv2 import GreengrassCoreIPCClientV2
from awsiot.greengrasscoreipc.model import (
    PublishMessage,
    JsonMessage
)
import time

ipc_client = GreengrassCoreIPCClientV2()

def on_sensor_data(event):
    """
    Receives temperature from sensor publisher component,
    processes it, and forwards to alert component
    """
    try:
        # Receive from publisher component.
        data = event.json_message.message
        sensor_id = data['sensor_id']
        temperature = data['temperature']
        
        print(f"Received from sensor {sensor_id}: {temperature}°F")
        
        # Process: Check if temperature is high.
        if temperature > 80:
            alert_data = {
                'sensor_id': sensor_id,
                'temperature': temperature,
                'alert': 'HIGH_TEMPERATURE'
            }
            
            # Publish to another component (AlertHandler).
            ipc_client.publish_to_topic(
                topic='component/alerts',
                publish_message=PublishMessage(
                    json_message=JsonMessage(message=alert_data)
                )
            )
            
            print(f"Alert sent to AlertHandler component")
    
    except Exception as e:
        print(f"Error processing sensor data: {e}")

def main():
    print("Temperature Processor component starting...")
    
    # Subscribe to sensor data from publisher component.
    ipc_client.subscribe_to_topic(
        topic='sensors/temperature',
        on_stream_event=on_sensor_data
    )
    
    print("Subscribed to sensors/temperature")
    print("Waiting for sensor data...")
    
    # Keep running.
    while True:
        time.sleep(1)

if __name__ == '__main__':
    main()

import software.amazon.awssdk.aws.greengrass.GreengrassCoreIPCClientV2;
import software.amazon.awssdk.aws.greengrass.model.PublishMessage;
import software.amazon.awssdk.aws.greengrass.model.PublishToTopicRequest;
import software.amazon.awssdk.aws.greengrass.model.JsonMessage;
import software.amazon.awssdk.aws.greengrass.model.SubscribeToTopicRequest;
import software.amazon.awssdk.aws.greengrass.model.SubscriptionResponseMessage;
import java.util.HashMap;
import java.util.Map;
import java.util.Optional;

public class TemperatureProcessor {
    private static GreengrassCoreIPCClientV2 ipcClient;

    public static void main(String[] args) {
        System.out.println("Temperature Processor component starting...");

        try (GreengrassCoreIPCClientV2 client = GreengrassCoreIPCClientV2.builder().build()) {
            ipcClient = client;

            SubscribeToTopicRequest subscribeRequest = new SubscribeToTopicRequest()
                .withTopic("sensors/temperature");

            ipcClient.subscribeToTopic(
                subscribeRequest, 
                TemperatureProcessor::onSensorData,
                Optional.empty(),
                Optional.empty()
            );

            System.out.println("Subscribed to sensors/temperature");
            System.out.println("Waiting for sensor data...");

            while (true) {
                Thread.sleep(1000);
            }
        } catch (Exception e) {
            System.err.println("Error: " + e.getMessage());
            e.printStackTrace();
        }
    }

    public static void onSensorData(SubscriptionResponseMessage message) {
        try {
            Map<String, Object> data = message.getJsonMessage().getMessage();
            String sensorId = (String) data.get("sensor_id");
            Number temp = (Number) data.get("temperature");
            int temperature = temp.intValue();

            System.out.println("Received from sensor " + sensorId + ": " + temperature + "F");

            if (temperature > 80) {
                Map<String, Object> alertData = new HashMap<>();
                alertData.put("sensor_id", sensorId);
                alertData.put("temperature", temperature);
                alertData.put("alert", "HIGH_TEMPERATURE");

                JsonMessage jsonMessage = new JsonMessage().withMessage(alertData);
                PublishMessage publishMessage = new PublishMessage().withJsonMessage(jsonMessage);
                PublishToTopicRequest publishRequest = new PublishToTopicRequest()
                    .withTopic("component/alerts")
                    .withPublishMessage(publishMessage);

                ipcClient.publishToTopic(publishRequest);
                System.out.println("Alert sent to AlertHandler component");
            }
        } catch (Exception e) {
            System.err.println("Error processing sensor data: " + e.getMessage());
        }
    }
}

const greengrasscoreipc = require('aws-iot-device-sdk-v2').greengrasscoreipc;

class TemperatureProcessor {
    constructor() {
        this.ipcClient = null;
    }

    async start() {
        console.log('Temperature Processor component starting...');
        
        try {
            this.ipcClient = greengrasscoreipc.createClient();
            await this.ipcClient.connect();
            
            const subscribeRequest = {
                topic: 'sensors/temperature'
            };

            const streamingOperation = this.ipcClient.subscribeToTopic(subscribeRequest);
            
            streamingOperation.on('message', (message) => {
                this.onSensorData(message);
            });
            
            streamingOperation.on('streamError', (error) => {
                console.error('Stream error:', error);
            });
            
            streamingOperation.on('ended', () => {
                console.log('Subscription stream ended');
            });
            
            await streamingOperation.activate();
            
            console.log('Subscribed to sensors/temperature');
            console.log('Waiting for sensor data...');
            
        } catch (error) {
            console.error('Error starting component:', error);
            process.exit(1);
        }
    }

    async onSensorData(message) {
        try {
            const data = message.jsonMessage.message;
            
            const sensorId = data.sensor_id;
            const temperature = data.temperature;
            
            console.log(`Received from sensor ${sensorId}: ${temperature}°F`);
            
            if (temperature > 80) {
                const alertData = {
                    sensor_id: sensorId,
                    temperature: temperature,
                    alert: 'HIGH_TEMPERATURE'
                };
                
                const publishRequest = {
                    topic: 'component/alerts',
                    publishMessage: {
                        jsonMessage: {
                            message: alertData
                        }
                    }
                };
                
                await this.ipcClient.publishToTopic(publishRequest);
                console.log('Alert sent to AlertHandler component');
            }
            
        } catch (error) {
            console.error('Error processing sensor data:', error);
        }
    }
}

// Start the component.
const processor = new TemperatureProcessor();
processor.start();

#include <gg/buffer.h>
#include <gg/error.h>
#include <gg/ipc/client.h>
#include <gg/map.h>
#include <gg/object.h>
#include <gg/sdk.h>
#include <unistd.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <pthread.h>

#define SUBSCRIBE_TOPIC "sensors/temperature"
#define PUBLISH_TOPIC "component/alerts"

typedef struct {
    char sensor_id[64];
    int64_t temperature;
} AlertData;

static pthread_mutex_t alert_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t alert_cond = PTHREAD_COND_INITIALIZER;
static AlertData pending_alert;
static bool has_pending_alert = false;

static void *alert_publisher_thread(void *arg) {
    (void) arg;
    
    while (true) {
        pthread_mutex_lock(&alert_mutex);
        while (!has_pending_alert) {
            pthread_cond_wait(&alert_cond, &alert_mutex);
        }
        
        AlertData alert = pending_alert;
        has_pending_alert = false;
        pthread_mutex_unlock(&alert_mutex);
        
        GgBuffer sensor_id_buf = { .data = (uint8_t *)alert.sensor_id, .len = strlen(alert.sensor_id) };
        GgMap payload = GG_MAP(
            gg_kv(GG_STR("sensor_id"), gg_obj_buf(sensor_id_buf)),
            gg_kv(GG_STR("temperature"), gg_obj_i64(alert.temperature)),
            gg_kv(GG_STR("alert"), gg_obj_buf(GG_STR("HIGH_TEMPERATURE")))
        );
        
        GgError ret = ggipc_publish_to_topic_json(GG_STR(PUBLISH_TOPIC), payload);
        
        if (ret != GG_ERR_OK) {
            fprintf(stderr, "Failed to publish alert\n");
        } else {
            printf("Alert sent to AlertHandler component\n");
        }
    }
    
    return NULL;
}

static void on_sensor_data(
    void *ctx, GgBuffer topic, GgObject payload, GgIpcSubscriptionHandle handle
) {
    (void) ctx;
    (void) topic;
    (void) handle;
    
    if (gg_obj_type(payload) != GG_TYPE_MAP) {
        fprintf(stderr, "Expected JSON message\n");
        return;
    }
    
    GgMap map = gg_obj_into_map(payload);
    
    GgObject *sensor_id_obj;
    if (!gg_map_get(map, GG_STR("sensor_id"), &sensor_id_obj)) {
        fprintf(stderr, "Missing sensor_id field\n");
        return;
    }
    GgBuffer sensor_id = gg_obj_into_buf(*sensor_id_obj);
    
    GgObject *temperature_obj;
    if (!gg_map_get(map, GG_STR("temperature"), &temperature_obj)) {
        fprintf(stderr, "Missing temperature field\n");
        return;
    }
    int64_t temperature = gg_obj_into_i64(*temperature_obj);
    
    printf("Received from sensor %.*s: %lld°F\n", 
           (int)sensor_id.len, sensor_id.data, (long long)temperature);
    
    if (temperature > 80) {
        pthread_mutex_lock(&alert_mutex);
        snprintf(pending_alert.sensor_id, sizeof(pending_alert.sensor_id),
                 "%.*s", (int)sensor_id.len, sensor_id.data);
        pending_alert.temperature = temperature;
        has_pending_alert = true;
        pthread_cond_signal(&alert_cond);
        pthread_mutex_unlock(&alert_mutex);
    }
}

int main(void) {
    setvbuf(stdout, NULL, _IONBF, 0);
    printf("Temperature Processor component starting...\n");
    
    gg_sdk_init();
    
    GgError ret = ggipc_connect();
    if (ret != GG_ERR_OK) {
        fprintf(stderr, "Failed to connect to Greengrass nucleus\n");
        exit(1);
    }
    printf("Connected to Greengrass IPC\n");
    
    // Start alert publisher thread.
    pthread_t alert_thread;
    if (pthread_create(&alert_thread, NULL, alert_publisher_thread, NULL) != 0) {
        fprintf(stderr, "Failed to create alert publisher thread\n");
        exit(1);
    }
    
    GgIpcSubscriptionHandle handle;
    ret = ggipc_subscribe_to_topic(
        GG_STR(SUBSCRIBE_TOPIC),
        &on_sensor_data,
        NULL,
        &handle
    );
    
    if (ret != GG_ERR_OK) {
        fprintf(stderr, "Failed to subscribe to topic\n");
        exit(1);
    }
    
    printf("Subscribed to %s\n", SUBSCRIBE_TOPIC);
    printf("Waiting for sensor data...\n");
    
    // Keep running.
    while (true) {
        sleep(1);
    }
    
    return 0;
}

#include <gg/ipc/client.hpp>
#include <gg/buffer.hpp>
#include <gg/object.hpp>
#include <gg/types.hpp>

#include <chrono>
#include <condition_variable>
#include <iostream>
#include <mutex>
#include <string>
#include <string_view>
#include <thread>

struct AlertData {
    std::string sensor_id;
    int64_t temperature;
};

static std::mutex alert_mutex;
static std::condition_variable alert_cv;
static AlertData pending_alert;
static bool has_pending_alert = false;

void alert_publisher_thread() {
    auto& client = gg::ipc::Client::get();
    
    while (true) {
        std::unique_lock<std::mutex> lock(alert_mutex);
        alert_cv.wait(lock, [] { return has_pending_alert; });
        
        AlertData alert = pending_alert;
        has_pending_alert = false;
        lock.unlock();
        
        // Create alert payload as JSON string.
        std::string json_payload = "{\"sensor_id\":\"" + alert.sensor_id + 
                                  "\",\"temperature\":" + std::to_string(alert.temperature) + 
                                  ",\"alert\":\"HIGH_TEMPERATURE\"}";
        
        // Convert to Buffer and publish.
        gg::Buffer buffer(json_payload);
        auto error = client.publish_to_topic("component/alerts", buffer);
        
        if (error) {
            std::cerr << "Failed to publish alert\n";
        } else {
            std::cout << "Alert sent to AlertHandler component\n";
        }
    }
}

class SensorCallback : public gg::ipc::LocalTopicCallback {
    void operator()(
        std::string_view topic,
        gg::Object payload,
        gg::ipc::Subscription& handle
    ) override {
        (void) topic;
        (void) handle;
        
        // Payload is a Buffer containing JSON string.
        if (payload.index() != GG_TYPE_BUF) {
            std::cerr << "Expected Buffer message\n";
            return;
        }
        
        // Extract buffer using gg::get.
        auto buffer = gg::get<std::span<uint8_t>>(payload);
        std::string json_str(reinterpret_cast<const char*>(buffer.data()), buffer.size());
        
        // Simple JSON parsing for demo.
        std::string sensor_id = "sensor1"; 
        int64_t temperature = 0;
        
        // Extract temperature (simple string search).
        size_t temp_pos = json_str.find("\"temperature\":");
        if (temp_pos != std::string::npos) {
            temp_pos += 14; // Skip "temperature".
            size_t end_pos = json_str.find_first_of(",}", temp_pos);
            if (end_pos != std::string::npos) {
                temperature = std::stoll(json_str.substr(temp_pos, end_pos - temp_pos));
            }
        }
        
        std::cout << "Received from sensor " << sensor_id << ": " 
                  << temperature << "°F\n";
        
        if (temperature > 80) {
            std::lock_guard<std::mutex> lock(alert_mutex);
            pending_alert = {sensor_id, temperature};
            has_pending_alert = true;
            alert_cv.notify_one();
        }
    }
};

int main() {
    // Disable stdout buffering for real-time logging.
    std::cout.setf(std::ios::unitbuf);
    
    std::cout << "Temperature Processor component starting..." << std::endl;
    
    auto& client = gg::ipc::Client::get();
    std::cout << "Got client instance" << std::endl;
    
    auto error = client.connect();
    std::cout << "Connect returned, error code: " << error.value() << std::endl;
    
    if (error) {
        std::cerr << "Failed to connect to Greengrass nucleus: " << error.message() << std::endl;
        return 1;
    }
    
    std::cout << "Connected to Greengrass IPC" << std::endl;
    
    // Start alert publisher thread.
    std::thread alert_thread(alert_publisher_thread);
    alert_thread.detach();
    
    // Handler must be static lifetime if subscription handle is not held.
    static SensorCallback handler;
    error = client.subscribe_to_topic("sensors/temperature", handler);
    
    if (error) {
        std::cerr << "Failed to subscribe to topic: " << error.message() << std::endl;
        return 1;
    }
    
    std::cout << "Subscribed to sensors/temperature" << std::endl;
    std::cout << "Waiting for sensor data..." << std::endl;
    
    // Keep running.
    while (true) {
        using namespace std::chrono_literals;
        std::this_thread::sleep_for(1s);
    }
    
    return 0;
}

Python does not require compilation. The component can use the .py file directly.

To build an executable JAR with all dependencies bundled:

To package your Node.js component with all dependencies:

Prerequisites:

To build the SDK and the component, you will need the following build dependencies:

Install build dependencies:

On Ubuntu/Debian:

sudo apt install build-essential cmake

On Amazon Linux:

sudo yum install gcc cmake make

Create a CMakeLists.txt file for your component:

cmake_minimum_required(VERSION 3.10)
project(TemperatureProcessor C)

set(CMAKE_C_STANDARD 11)

# Add AWS Greengrass Component SDK
add_subdirectory(aws-greengrass-component-sdk)

# Build your component executable
add_executable(temperature_processor temperature_processor.c)
target_link_libraries(temperature_processor gg-sdk)

Build steps:

# Clone the AWS Greengrass Component SDK into your project
git clone https://github.com/aws-greengrass/aws-greengrass-component-sdk.git

# Build your component
cmake -B build -D CMAKE_BUILD_TYPE=MinSizeRel
make -C build -j$(nproc)

# The binary 'temperature_processor' is in ./build/
# Upload this binary to S3 for deployment

Prerequisites:

To build the SDK and the component, you will need the following build dependencies:

Install build dependencies:

On Ubuntu/Debian:

sudo apt install build-essential cmake

On Amazon Linux:

sudo yum install gcc-c++ cmake make

Create a CMakeLists.txt file for your component:

cmake_minimum_required(VERSION 3.10)
project(TemperatureProcessor CXX)

set(CMAKE_CXX_STANDARD 20)

# Add SDK as subdirectory
add_subdirectory(aws-greengrass-component-sdk)

# Add C++ SDK subdirectory
add_subdirectory(aws-greengrass-component-sdk/cpp)

add_executable(temperature_processor temperature_processor.cpp)
target_link_libraries(temperature_processor gg-sdk++)

Build steps:

# Clone the AWS Greengrass Component SDK into your project
git clone https://github.com/aws-greengrass/aws-greengrass-component-sdk.git

# Build your component
cmake -B build -D CMAKE_BUILD_TYPE=MinSizeRel
make -C build -j$(nproc)

# The binary 'temperature_processor' will be in ./build/
# Upload this binary to S3 for deployment

{
  "RecipeFormatVersion": "2020-01-25",
  "ComponentName": "com.example.TemperatureProcessor",
  "ComponentVersion": "1.0.0",
  "ComponentType": "aws.greengrass.generic",
  "ComponentDescription": "Receives sensor data and forwards alerts to AlertHandler",
  "ComponentPublisher": "[Your Company]",
  "ComponentConfiguration": {
    "DefaultConfiguration": {
      "accessControl": {
        "aws.greengrass.ipc.pubsub": {
          "com.example.TemperatureProcessor:pubsub:1": {
            "policyDescription": "Allows access to subscribe to sensor topics",
            "operations": [
              "aws.greengrass#SubscribeToTopic"
            ],
            "resources": [
              "sensors/temperature"
            ]
          },
          "com.example.TemperatureProcessor:pubsub:2": {
            "policyDescription": "Allows access to publish to alert topics",
            "operations": [
              "aws.greengrass#PublishToTopic"
            ],
            "resources": [
              "component/alerts"
            ]
          }
        }
      }
    }
  },
  "Manifests": [
    {
      "Platform": {
        "os": "linux",
        "runtime": "*"
      },
      "Lifecycle": {
        "run": "python3 -u {artifacts:path}/temperature_processor.py"
      },
      "Artifacts": [
        {
          "Uri": "s3://YOUR-BUCKET/artifacts/com.example.TemperatureProcessor/1.0.0/temperature_processor.py"
        }
      ]
    }
  ]
}

{
  "RecipeFormatVersion": "2020-01-25",
  "ComponentName": "com.example.TemperatureProcessor",
  "ComponentVersion": "1.0.0",
  "ComponentType": "aws.greengrass.generic",
  "ComponentDescription": "Receives sensor data and forwards alerts to AlertHandler",
  "ComponentPublisher": "[Your Company]",
  "ComponentConfiguration": {
    "DefaultConfiguration": {
      "accessControl": {
        "aws.greengrass.ipc.pubsub": {
          "com.example.TemperatureProcessor:pubsub:1": {
            "policyDescription": "Allows access to subscribe to sensor topics",
            "operations": [
              "aws.greengrass#SubscribeToTopic"
            ],
            "resources": [
              "sensors/temperature"
            ]
          },
          "com.example.TemperatureProcessor:pubsub:2": {
            "policyDescription": "Allows access to publish to alert topics",
            "operations": [
              "aws.greengrass#PublishToTopic"
            ],
            "resources": [
              "component/alerts"
            ]
          }
        }
      }
    }
  },
  "Manifests": [
    {
      "Platform": {
        "os": "linux",
        "runtime": "*"
      },
      "Lifecycle": {
        "run": "java -jar {artifacts:path}/TemperatureProcessor.jar"
      },
      "Artifacts": [
        {
          "Uri": "s3://YOUR-BUCKET/artifacts/com.example.TemperatureProcessor/1.0.0/TemperatureProcessor.jar"
        }
      ]
    }
  ]
}

{
  "RecipeFormatVersion": "2020-01-25",
  "ComponentName": "com.example.TemperatureProcessor",
  "ComponentVersion": "1.0.0",
  "ComponentType": "aws.greengrass.generic",
  "ComponentDescription": "Receives sensor data and forwards alerts to AlertHandler",
  "ComponentPublisher": "[Your Company]",
  "ComponentConfiguration": {
    "DefaultConfiguration": {
      "accessControl": {
        "aws.greengrass.ipc.pubsub": {
          "com.example.TemperatureProcessor:pubsub:1": {
            "policyDescription": "Allows access to subscribe to sensor topics",
            "operations": [
              "aws.greengrass#SubscribeToTopic"
            ],
            "resources": [
              "sensors/temperature"
            ]
          },
          "com.example.TemperatureProcessor:pubsub:2": {
            "policyDescription": "Allows access to publish to alert topics",
            "operations": [
              "aws.greengrass#PublishToTopic"
            ],
            "resources": [
              "component/alerts"
            ]
          }
        }
      }
    }
  },
  "Manifests": [
    {
      "Platform": {
        "os": "linux",
        "runtime": "*"
      },
      "Lifecycle": {
        "run": "cd {artifacts:decompressedPath}/TemperatureProcessor && node TemperatureProcessor.js"
      },
      "Artifacts": [
        {
          "Uri": "s3://YOUR-BUCKET/artifacts/com.example.TemperatureProcessor/1.0.0/TemperatureProcessor.zip",
          "Unarchive": "ZIP"
        }
      ]
    }
  ]
}

{
  "RecipeFormatVersion": "2020-01-25",
  "ComponentName": "com.example.TemperatureProcessor",
  "ComponentVersion": "1.0.0",
  "ComponentType": "aws.greengrass.generic",
  "ComponentDescription": "Receives sensor data and forwards alerts to AlertHandler",
  "ComponentPublisher": "[Your Company]",
  "ComponentConfiguration": {
    "DefaultConfiguration": {
      "accessControl": {
        "aws.greengrass.ipc.pubsub": {
          "com.example.TemperatureProcessor:pubsub:1": {
            "policyDescription": "Allows access to subscribe to sensor topics",
            "operations": [
              "aws.greengrass#SubscribeToTopic"
            ],
            "resources": [
              "sensors/temperature"
            ]
          },
          "com.example.TemperatureProcessor:pubsub:2": {
            "policyDescription": "Allows access to publish to alert topics",
            "operations": [
              "aws.greengrass#PublishToTopic"
            ],
            "resources": [
              "component/alerts"
            ]
          }
        }
      }
    }
  },
  "Manifests": [
    {
      "Platform": {
        "os": "linux",
        "runtime": "*"
      },
      "Lifecycle": {
        "run": "{artifacts:path}/temperature_processor"
      },
      "Artifacts": [
        {
          "Uri": "s3://YOUR-BUCKET/artifacts/com.example.TemperatureProcessor/1.0.0/temperature_processor"
        }
      ]
    }
  ]
}

import greengrasssdk
import json
import time

iot_client = greengrasssdk.client('iot-data')

def lambda_handler(event, context):
    """
    Receives commands from IoT Core,
    processes them, and sends telemetry back to cloud
    """
    # Receive command from IoT Core.
    command = event.get('command')
    device_id = event.get('device_id', 'device1')

    print(f"Received command from cloud: {command}")

    # Process command.
    if command == 'get_status':
        status = get_device_status()

        # Send telemetry back to IoT Core.
        telemetry_data = {
            'device_id': device_id,
            'status': status,
            'timestamp': time.time()
        }

        iot_client.publish(
            topic=f'telemetry/{device_id}',
            payload=json.dumps(telemetry_data)
        )

        print(f"Telemetry sent to cloud: {telemetry_data}")

    return {'statusCode': 200}

def get_device_status():
    """Get current device status"""
    # Simulate getting device status.
    return 'online'

import com.amazonaws.services.lambda.runtime.Context;
import com.amazonaws.greengrass.javasdk.IotDataClient;
import com.amazonaws.greengrass.javasdk.model.PublishRequest;
import com.google.gson.Gson;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;

public class DeviceControllerLambda {
    private static final Gson gson = new Gson();
    private final IotDataClient iotDataClient;

    public DeviceControllerLambda() {
        this.iotDataClient = new IotDataClient();
    }

    public String handleRequest(Map<String, Object> event, Context context) {
        /*
         * Receives commands from IoT Core,
         * processes them, and sends telemetry back to cloud
         */

        // Receive command from IoT Core.
        String command = (String) event.get("command");
        String deviceId = event.containsKey("device_id") ? 
            (String) event.get("device_id") : "device1";

        System.out.println("Received command from cloud: " + command);

        // Process command.
        if ("get_status".equals(command)) {
            String status = getDeviceStatus();

            // Send telemetry back to IoT Core.
            Map<String, Object> telemetryData = new HashMap<>();
            telemetryData.put("device_id", deviceId);
            telemetryData.put("status", status);
            telemetryData.put("timestamp", System.currentTimeMillis() / 1000.0);

            String payload = gson.toJson(telemetryData);
            PublishRequest publishRequest = new PublishRequest()
                .withTopic("telemetry/" + deviceId)
                .withPayload(ByteBuffer.wrap(payload.getBytes(StandardCharsets.UTF_8)));

            iotDataClient.publish(publishRequest);

            System.out.println("Telemetry sent to cloud: " + telemetryData);
        }

        return "Success";
    }

    private String getDeviceStatus() {
        // Simulate getting device status.
        return "online";
    }
}

const greengrasssdk = require('aws-greengrass-core-sdk');

const iotClient = new greengrasssdk.IotData();

/**
 * Receives commands from IoT Core and sends telemetry back.
 */
exports.handler = function(event, context) {
    console.log('Received command from IoT Core:', JSON.stringify(event));
    
    const command = event.command;
    const deviceId = event.device_id || 'device1';
    
    console.log(`Processing command: ${command}`);
    
    if (command === 'get_status') {
        const status = 'online';
        
        const telemetryData = {
            device_id: deviceId,
            status: status,
            timestamp: Date.now() / 1000
        };
        
        // Publish telemetry to IoT Core using greengrasssdk.
        const params = {
            topic: `telemetry/${deviceId}`,
            payload: JSON.stringify(telemetryData)
        };
        
        iotClient.publish(params, (err) => {
            if (err) {
                console.error('Error publishing telemetry:', err);
                context.fail(err);
            } else {
                console.log('Telemetry sent to IoT Core:', JSON.stringify(telemetryData));
                context.succeed('Success');
            }
        });
    } else {
        context.succeed('Success');
    }
};

#include <aws/greengrass/greengrasssdk.h>
#include <stdio.h>
#include <string.h>
#include <jansson.h>
#include <time.h>

static aws_greengrass_iot_data_client *iot_client = NULL;

const char* get_device_status(void) {
    // Simulate getting device status.
    return "online";
}

void on_cloud_command(const char *topic, const uint8_t *payload, size_t payload_len, void *user_data) {
    // Parse incoming command from IoT Core.
    char *payload_str = strndup((char *)payload, payload_len);
    json_error_t error;
    json_t *event = json_loads(payload_str, 0, &error);
    free(payload_str);
    
    if (!event) {
        fprintf(stderr, "Error parsing JSON: %s\n", error.text);
        return;
    }
    
    // Extract command and device_id.
    json_t *command_obj = json_object_get(event, "command");
    json_t *device_id_obj = json_object_get(event, "device_id");
    
    const char *command = json_string_value(command_obj);
    const char *device_id = device_id_obj ? json_string_value(device_id_obj) : "device1";
    
    printf("Received command from cloud: %s\n", command);
    
    // Process command.
    if (command && strcmp(command, "get_status") == 0) {
        const char *status = get_device_status();
        
        // Send telemetry back to IoT Core.
        json_t *telemetry_data = json_object();
        json_object_set_new(telemetry_data, "device_id", json_string(device_id));
        json_object_set_new(telemetry_data, "status", json_string(status));
        json_object_set_new(telemetry_data, "timestamp", json_real(time(NULL)));
        
        char *telemetry_payload = json_dumps(telemetry_data, JSON_COMPACT);
        
        // Publish telemetry to IoT Core.
        char telemetry_topic[256];
        snprintf(telemetry_topic, sizeof(telemetry_topic), "telemetry/%s", device_id);
        
        aws_greengrass_publish_params params = {
            .topic = telemetry_topic,
            .payload = (uint8_t *)telemetry_payload,
            .payload_len = strlen(telemetry_payload)
        };
        
        aws_greengrass_iot_data_publish(iot_client, &params);
        
        printf("Telemetry sent to cloud: %s\n", telemetry_payload);
    
        free(telemetry_payload);
        json_decref(telemetry_data);
    }
    
    json_decref(event);
}

int main(int argc, char *argv[]) {
    // Initialize Greengrass SDK.
    iot_client = aws_greengrass_iot_data_client_new();
    
    // Subscribe to commands from IoT Core.
    aws_greengrass_subscribe_params subscribe_params = {
        .topic = "commands/device1",
        .callback = on_cloud_command,
        .user_data = NULL
    };
    
    aws_greengrass_iot_data_subscribe(iot_client, &subscribe_params);
    
    printf("Device Controller Lambda started\n");
    printf("Subscribed to commands/device1\n");
    printf("Waiting for commands from IoT Core...\n");
    
    // Keep the Lambda running.
    while (1) {
        sleep(1);
    }
    
    return 0;
}

#include <aws/greengrass/greengrasssdk.h>
#include <iostream>
#include <string>
#include <memory>
#include <jansson.h>
#include <ctime>
#include <unistd.h>

class DeviceController {
private:
    std::unique_ptr<aws_greengrass_iot_data_client, decltype(&aws_greengrass_iot_data_client_destroy)> iot_client;
    
    static void message_callback_wrapper(const char *topic, const uint8_t *payload, 
                                        size_t payload_len, void *user_data) {
        auto* controller = static_cast<DeviceController*>(user_data);
        controller->on_cloud_command(topic, payload, payload_len);
    }
    
    std::string get_device_status() {
        // Simulate getting device status.
        return "online";
    }

public:
    DeviceController() 
        : iot_client(aws_greengrass_iot_data_client_new(), 
                     aws_greengrass_iot_data_client_destroy) {
        if (!iot_client) {
            throw std::runtime_error("Failed to create Greengrass IoT client");
        }
    }
    
    void on_cloud_command(const char *topic, const uint8_t *payload, size_t payload_len) {
        // Parse incoming command from IoT Core.
        std::string payload_str(reinterpret_cast<const char*>(payload), payload_len);
        
        json_error_t error;
        json_t *event = json_loads(payload_str.c_str(), 0, &error);
        
        if (!event) {
            std::cerr << "Error parsing JSON: " << error.text << std::endl;
            return;
        }
        
        // Extract command and device_id.
        json_t *command_obj = json_object_get(event, "command");
        json_t *device_id_obj = json_object_get(event, "device_id");
        
        const char *command = json_string_value(command_obj);
        const char *device_id = device_id_obj ? json_string_value(device_id_obj) : "device1";
        
        std::cout << "Received command from cloud: " << command << std::endl;
        
        // Process command.
        if (command && std::string(command) == "get_status") {
            std::string status = get_device_status();
            
            // Send telemetry back to IoT Core.
            json_t *telemetry_data = json_object();
            json_object_set_new(telemetry_data, "device_id", json_string(device_id));
            json_object_set_new(telemetry_data, "status", json_string(status.c_str()));
            json_object_set_new(telemetry_data, "timestamp", json_real(std::time(nullptr)));
            
            char *telemetry_payload = json_dumps(telemetry_data, JSON_COMPACT);
            
            // Publish telemetry to IoT Core.
            std::string telemetry_topic = "telemetry/" + std::string(device_id);
            
            aws_greengrass_publish_params params = {
                .topic = telemetry_topic.c_str(),
                .payload = reinterpret_cast<uint8_t*>(telemetry_payload),
                .payload_len = strlen(telemetry_payload)
            };
            
            aws_greengrass_iot_data_publish(iot_client.get(), &params);
            
            std::cout << "Telemetry sent to cloud: " << telemetry_payload << std::endl;
            
            free(telemetry_payload);
            json_decref(telemetry_data);
        }
        
        json_decref(event);
    }
    
    void subscribe_to_topic(const std::string& topic) {
        aws_greengrass_subscribe_params subscribe_params = {
            .topic = topic.c_str(),
            .callback = message_callback_wrapper,
            .user_data = this
        };
        
        aws_greengrass_iot_data_subscribe(iot_client.get(), &subscribe_params);
        
        std::cout << "Device Controller Lambda started" << std::endl;
        std::cout << "Subscribed to " << topic << std::endl;
        std::cout << "Waiting for commands from IoT Core..." << std::endl;
    }
    
    void run() {
        // Keep the Lambda running.
        while (true) {
            sleep(1);
        }
    }
};

int main(int argc, char *argv[]) {
    try {
        DeviceController controller;
        controller.subscribe_to_topic("commands/device1");
        controller.run();
    } catch (const std::exception& e) {
        std::cerr << "Error: " << e.what() << std::endl;
        return 1;
    }
    
    return 0;
}

Prerequisites: Before using this component code, install and verify the Amazon IoT Device SDK for Python on your Greengrass device:

# Install the SDK
pip3 install awsiotsdk

# Verify installation
python3 -c "import awsiot.greengrasscoreipc.clientv2; print('SDK installed successfully')"

If you encounter dependency conflicts during installation, try installing a specific version of the Amazon IoT Device SDK.

If the verification command prints "SDK installed successfully", you're ready to use the component code:

from awsiot.greengrasscoreipc.clientv2 import GreengrassCoreIPCClientV2
from awsiot.greengrasscoreipc.model import QOS
import json
import time

ipc_client = GreengrassCoreIPCClientV2()

def on_command(event):
    """
    Receives commands from IoT Core,
    processes them, and sends telemetry back to cloud
    """
    try:
        # Receive command from IoT Core.
        data = json.loads(event.message.payload.decode('utf-8'))
        command = data.get('command')
        device_id = data.get('device_id', 'device1')

        print(f"Received command from cloud: {command}")

        # Process command.
        if command == 'get_status':
            status = get_device_status()

            # Send telemetry back to IoT Core.
            telemetry_data = {
                'device_id': device_id,
                'status': status,
                'timestamp': time.time()
            }

            ipc_client.publish_to_iot_core(
                topic_name=f'telemetry/{device_id}',
                qos=QOS.AT_LEAST_ONCE,
                payload=json.dumps(telemetry_data).encode('utf-8')
            )

            print(f"Telemetry sent to cloud: {telemetry_data}")

    except Exception as e:
        print(f"Error processing command: {e}")

def get_device_status():
    """Get current device status"""
    # Simulate getting device status.
    return 'online'

def main():
    print("Device Controller component starting...")

    # Subscribe to commands from IoT Core.
    ipc_client.subscribe_to_iot_core(
        topic_name='commands/device1',
        qos=QOS.AT_LEAST_ONCE,
        on_stream_event=on_command
    )

    print("Subscribed to commands/device1 from IoT Core")
    print("Waiting for commands from cloud...")

    # Keep running.
    while True:
        time.sleep(1)

if __name__ == '__main__':
    main()

import software.amazon.awssdk.aws.greengrass.GreengrassCoreIPCClientV2;
import software.amazon.awssdk.aws.greengrass.model.QOS;
import software.amazon.awssdk.aws.greengrass.model.SubscribeToIoTCoreRequest;
import software.amazon.awssdk.aws.greengrass.model.IoTCoreMessage;
import software.amazon.awssdk.aws.greengrass.model.PublishToIoTCoreRequest;
import java.nio.charset.StandardCharsets;
import java.util.Optional;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

public class DeviceController {
    private static GreengrassCoreIPCClientV2 ipcClient;

    public static void main(String[] args) {
        System.out.println("Device Controller component starting...");
        
        try (GreengrassCoreIPCClientV2 client = GreengrassCoreIPCClientV2.builder().build()) {
            ipcClient = client;

            SubscribeToIoTCoreRequest subscribeRequest = new SubscribeToIoTCoreRequest()
                .withTopicName("commands/device1")
                .withQos(QOS.AT_LEAST_ONCE);

            ipcClient.subscribeToIoTCore(
                subscribeRequest,
                DeviceController::onCommand,
                Optional.empty(),
                Optional.empty()
            );

            System.out.println("Subscribed to commands/device1 from IoT Core");
            System.out.println("Waiting for commands from cloud...");

            while (true) {
                Thread.sleep(1000);
            }
        } catch (Exception e) {
            System.err.println("Error: " + e.getMessage());
            e.printStackTrace();
        }
    }

    public static void onCommand(IoTCoreMessage message) {
        try {
            String payload = new String(message.getMessage().getPayload(), StandardCharsets.UTF_8);
            
            // Simple JSON parsing.
            String command = extractJsonValue(payload, "command");
            String deviceId = extractJsonValue(payload, "device_id");
            if (deviceId == null || deviceId.isEmpty()) {
                deviceId = "device1";
            }

            System.out.println("Received command from cloud: " + command);

            if ("get_status".equals(command)) {
                String status = getDeviceStatus();

                // Build JSON manually.
                String telemetryJson = String.format(
                    "{\"device_id\":\"%s\",\"status\":\"%s\",\"timestamp\":%.3f}",
                    deviceId, status, System.currentTimeMillis() / 1000.0
                );
                byte[] telemetryBytes = telemetryJson.getBytes(StandardCharsets.UTF_8);

                PublishToIoTCoreRequest publishRequest = new PublishToIoTCoreRequest()
                    .withTopicName("telemetry/" + deviceId)
                    .withQos(QOS.AT_LEAST_ONCE)
                    .withPayload(telemetryBytes);

                ipcClient.publishToIoTCore(publishRequest);

                System.out.println("Telemetry sent to cloud: " + telemetryJson);
            }
        } catch (Exception e) {
            System.err.println("Error processing command: " + e.getMessage());
        }
    }

    private static String extractJsonValue(String json, String key) {
        Pattern pattern = Pattern.compile("\"" + Pattern.quote(key) + "\"\\s*:\\s*\"([^\"]+)\"");
        Matcher matcher = pattern.matcher(json);
        return matcher.find() ? matcher.group(1) : null;
    }

    private static String getDeviceStatus() {
        return "online";
    }
}

const greengrasscoreipc = require('aws-iot-device-sdk-v2').greengrasscoreipc;

class DeviceController {
    constructor() {
        this.ipcClient = null;
    }

    async start() {
        console.log('Device Controller component starting...');
        
        try {
            this.ipcClient = greengrasscoreipc.createClient();
            await this.ipcClient.connect();
            
            const subscribeRequest = {
                topicName: 'commands/device1',
                qos: 1
            };

            const streamingOperation = this.ipcClient.subscribeToIoTCore(subscribeRequest);
            
            streamingOperation.on('message', (message) => {
                this.onCommand(message);
            });
            
            streamingOperation.on('streamError', (error) => {
                console.error('Stream error:', error);
            });
            
            streamingOperation.on('ended', () => {
                console.log('Subscription stream ended');
            });
            
            await streamingOperation.activate();
            
            console.log('Subscribed to commands/device1 from IoT Core');
            console.log('Waiting for commands from cloud...');
            
        } catch (error) {
            console.error('Error starting component:', error);
            process.exit(1);
        }
    }

    async onCommand(message) {
        try {
            const payload = message.message.payload.toString('utf-8');
            const data = JSON.parse(payload);
            
            const command = data.command;
            const deviceId = data.device_id || 'device1';
            
            console.log(`Received command from cloud: ${command}`);
            
            if (command === 'get_status') {
                const status = this.getDeviceStatus();
                
                const telemetryData = {
                    device_id: deviceId,
                    status: status,
                    timestamp: Date.now() / 1000
                };
                
                const telemetryJson = JSON.stringify(telemetryData);
                
                const publishRequest = {
                    topicName: `telemetry/${deviceId}`,
                    qos: 1,
                    payload: Buffer.from(telemetryJson, 'utf-8')
                };
                
                await this.ipcClient.publishToIoTCore(publishRequest);
                console.log(`Telemetry sent to cloud: ${telemetryJson}`);
            }
            
        } catch (error) {
            console.error('Error processing command:', error);
        }
    }

    getDeviceStatus() {
        return 'online';
    }
}

// Start the component.
const controller = new DeviceController();
controller.start();

#include <gg/buffer.h>
#include <gg/error.h>
#include <gg/ipc/client.h>
#include <gg/map.h>
#include <gg/object.h>
#include <gg/sdk.h>
#include <unistd.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <pthread.h>

#define COMMAND_TOPIC "commands/device1"
#define TELEMETRY_TOPIC "telemetry/device1"

typedef struct {
    char device_id[64];
    char command[64];
} CommandData;

static pthread_mutex_t command_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t command_cond = PTHREAD_COND_INITIALIZER;
static CommandData pending_command;
static bool has_pending_command = false;

const char* get_device_status(void) {
    // Simulate getting device status.
    return "online";
}

static void *telemetry_publisher_thread(void *arg) {
    (void) arg;
    
    while (true) {
        pthread_mutex_lock(&command_mutex);
        while (!has_pending_command) {
            pthread_cond_wait(&command_cond, &command_mutex);
        }
        
        CommandData cmd = pending_command;
        has_pending_command = false;
        pthread_mutex_unlock(&command_mutex);
        
        // Process command.
        if (strcmp(cmd.command, "get_status") == 0) {
            const char *status = get_device_status();
            
            // Create telemetry JSON string.
            char telemetry_json[512];
            snprintf(telemetry_json, sizeof(telemetry_json),
                     "{\"device_id\":\"%s\",\"status\":\"%s\",\"timestamp\":%ld}",
                     cmd.device_id, status, time(NULL));
            
            GgBuffer telemetry_buf = {
                .data = (uint8_t *)telemetry_json,
                .len = strlen(telemetry_json)
            };
            
            // Publish telemetry to IoT Core.
            GgError ret = ggipc_publish_to_iot_core(GG_STR(TELEMETRY_TOPIC), telemetry_buf, 0);
            
            if (ret != GG_ERR_OK) {
                fprintf(stderr, "Failed to publish telemetry to IoT Core\n");
            } else {
                printf("Telemetry sent to cloud: device_id=%s, status=%s\n", cmd.device_id, status);
            }
        }
    }
    
    return NULL;
}

static void on_cloud_command(
    void *ctx, GgBuffer topic, GgBuffer payload, GgIpcSubscriptionHandle handle
) {
    (void) ctx;
    (void) topic;
    (void) handle;
    
    printf("Received command from IoT Core: %.*s\n", (int)payload.len, payload.data);
    
    // Parse JSON payload (comes as raw buffer from IoT Core).
    // For simplicity, we'll do basic string parsing.
    
    // Extract command and device_id from JSON string.
    char payload_str[512];
    snprintf(payload_str, sizeof(payload_str), "%.*s", (int)payload.len, payload.data);
    
    // Simple JSON parsing (looking for "command":"get_status").
    char *command_start = strstr(payload_str, "\"command\"");
    char *device_id_start = strstr(payload_str, "\"device_id\"");
    
    if (command_start) {
        pthread_mutex_lock(&command_mutex);
        
        char *cmd_value = strstr(command_start, ":");
        if (cmd_value) {
            cmd_value = strchr(cmd_value, '"');
            if (cmd_value) {
                cmd_value++;
                char *cmd_end = strchr(cmd_value, '"');
                if (cmd_end) {
                    size_t cmd_len = cmd_end - cmd_value;
                    if (cmd_len < sizeof(pending_command.command)) {
                        strncpy(pending_command.command, cmd_value, cmd_len);
                        pending_command.command[cmd_len] = '\0';
                    }
                }
            }
        }
        
        // Extract device_id or use default.
        if (device_id_start) {
            char *dev_value = strstr(device_id_start, ":");
            if (dev_value) {
                dev_value = strchr(dev_value, '"');
                if (dev_value) {
                    dev_value++;
                    char *dev_end = strchr(dev_value, '"');
                    if (dev_end) {
                        size_t dev_len = dev_end - dev_value;
                        if (dev_len < sizeof(pending_command.device_id)) {
                            strncpy(pending_command.device_id, dev_value, dev_len);
                            pending_command.device_id[dev_len] = '\0';
                        }
                    }
                }
            }
        } else {
            strcpy(pending_command.device_id, "device1");
        }
        
        printf("Received command from cloud: %s\n", pending_command.command);
        
        has_pending_command = true;
        pthread_cond_signal(&command_cond);
        pthread_mutex_unlock(&command_mutex);
    }
}

int main(void) {
    setvbuf(stdout, NULL, _IONBF, 0);
    printf("Device Controller component starting...\n");
    
    gg_sdk_init();
    
    GgError ret = ggipc_connect();
    if (ret != GG_ERR_OK) {
        fprintf(stderr, "Failed to connect to Greengrass nucleus\n");
        exit(1);
    }
    printf("Connected to Greengrass IPC\n");
    
    // Start telemetry publisher thread.
    pthread_t telemetry_thread;
    if (pthread_create(&telemetry_thread, NULL, telemetry_publisher_thread, NULL) != 0) {
        fprintf(stderr, "Failed to create telemetry publisher thread\n");
        exit(1);
    }
    
    // Subscribe to commands from IoT Core.
    GgIpcSubscriptionHandle handle;
    ret = ggipc_subscribe_to_iot_core(
        GG_STR(COMMAND_TOPIC),
        0,
        &on_cloud_command,
        NULL,
        &handle
    );
    
    if (ret != GG_ERR_OK) {
        fprintf(stderr, "Failed to subscribe to IoT Core topic\n");
        exit(1);
    }
    
    printf("Subscribed to %s\n", COMMAND_TOPIC);
    printf("Waiting for commands from IoT Core...\n");
    
    while (true) {
        sleep(1);
    }
    
    return 0;
}

#include <gg/ipc/client.hpp>
#include <gg/buffer.hpp>
#include <gg/object.hpp>
#include <gg/types.hpp>

#include <chrono>
#include <condition_variable>
#include <ctime>
#include <iostream>
#include <mutex>
#include <string>
#include <string_view>
#include <thread>

constexpr std::string_view COMMAND_TOPIC = "commands/device1";
constexpr std::string_view TELEMETRY_TOPIC = "telemetry/device1";

struct CommandData {
    std::string device_id;
    std::string command;
};

static std::mutex command_mutex;
static std::condition_variable command_cv;
static CommandData pending_command;
static bool has_pending_command = false;

std::string get_device_status() {
    // Simulate getting device status.
    return "online";
}

void telemetry_publisher_thread() {
    auto& client = gg::ipc::Client::get();
    
    while (true) {
        std::unique_lock<std::mutex> lock(command_mutex);
        command_cv.wait(lock, [] { return has_pending_command; });
        
        CommandData cmd = pending_command;
        has_pending_command = false;
        lock.unlock();
        
        // Process command.
        if (cmd.command == "get_status") {
            std::string status = get_device_status();
            
            // Get current timestamp.
            auto now = std::time(nullptr);
            
            // Create telemetry JSON payload.
            std::string telemetry_payload = "{\"device_id\":\"" + cmd.device_id + 
                                          "\",\"status\":\"" + status + 
                                          "\",\"timestamp\":" + std::to_string(now) + "}";
            
            // Publish telemetry to IoT Core.
            gg::Buffer telemetry_buffer(telemetry_payload);
            auto error = client.publish_to_iot_core(TELEMETRY_TOPIC, telemetry_buffer);
            
            if (error) {
                std::cerr << "Failed to publish telemetry to IoT Core: " 
                         << error.message() << std::endl;
            } else {
                std::cout << "Telemetry sent to cloud: device_id=" << cmd.device_id 
                         << ", status=" << status << std::endl;
            }
        }
    }
}

class CloudCommandCallback : public gg::ipc::IoTCoreTopicCallback {
    void operator()(
        std::string_view topic,
        gg::Object payload,
        gg::ipc::Subscription& handle
    ) override {
        (void) topic;
        (void) handle;
        
        // Payload is a Buffer containing JSON string from IoT Core.
        if (payload.index() != GG_TYPE_BUF) {
            std::cerr << "Expected Buffer message\n";
            return;
        }
        
        // Extract buffer.
        auto buffer = gg::get<std::span<uint8_t>>(payload);
        std::string json_str(reinterpret_cast<const char*>(buffer.data()), buffer.size());
        
        std::cout << "Received command from IoT Core: " << json_str << std::endl;
        
        // Simple JSON parsing for demo.
        std::string command;
        std::string device_id = "device1";  // Default
        
        // Extract command.
        size_t cmd_pos = json_str.find("\"command\":");
        if (cmd_pos != std::string::npos) {
            size_t start = json_str.find("\"", cmd_pos + 10) + 1;
            size_t end = json_str.find("\"", start);
            if (end != std::string::npos) {
                command = json_str.substr(start, end - start);
            }
        }
        
        // Extract device_id if present.
        size_t dev_pos = json_str.find("\"device_id\":");
        if (dev_pos != std::string::npos) {
            size_t start = json_str.find("\"", dev_pos + 12) + 1;
            size_t end = json_str.find("\"", start);
            if (end != std::string::npos) {
                device_id = json_str.substr(start, end - start);
            }
        }
        
        if (!command.empty()) {
            std::lock_guard<std::mutex> lock(command_mutex);
            pending_command = {device_id, command};
            has_pending_command = true;
            command_cv.notify_one();
            
            std::cout << "Received command from cloud: " << command << std::endl;
        }
    }
};

int main() {
    // Disable stdout buffering for real-time logging in systemd/Greengrass.
    std::cout.setf(std::ios::unitbuf);
    
    std::cout << "Device Controller component starting..." << std::endl;
    
    auto& client = gg::ipc::Client::get();
    
    auto error = client.connect();
    if (error) {
        std::cerr << "Failed to connect to Greengrass nucleus: " 
                 << error.message() << std::endl;
        return 1;
    }
    
    std::cout << "Connected to Greengrass IPC" << std::endl;
    
    // Start telemetry publisher thread.
    std::thread telemetry_thread(telemetry_publisher_thread);
    telemetry_thread.detach();
    
    // Subscribe to commands from IoT Core.
    static CloudCommandCallback handler;
    error = client.subscribe_to_iot_core(COMMAND_TOPIC, handler);
    
    if (error) {
        std::cerr << "Failed to subscribe to IoT Core topic: " 
                 << error.message() << std::endl;
        return 1;
    }
    
    std::cout << "Subscribed to " << COMMAND_TOPIC << std::endl;
    std::cout << "Waiting for commands from IoT Core..." << std::endl;
    
    // Keep running.
    while (true) {
        using namespace std::chrono_literals;
        std::this_thread::sleep_for(1s);
    }
    
    return 0;
}

Python does not require compilation. The component can use the .py file directly.

To build an executable JAR with all dependencies bundled:

To package your Node.js component with all dependencies:

Prerequisites:

To build the SDK and the component, you will need the following build dependencies:

Install build dependencies:

On Ubuntu/Debian:

sudo apt install build-essential cmake

On Amazon Linux:

sudo yum install gcc cmake make

Create a CMakeLists.txt file for your component:

cmake_minimum_required(VERSION 3.10)
project(DeviceController C)

set(CMAKE_C_STANDARD 11)

# Add AWS Greengrass Component SDK
add_subdirectory(aws-greengrass-component-sdk)

# Build your component executable
add_executable(device_controller device_controller.c)
target_link_libraries(device_controller gg-sdk)

Build steps:

# Clone the AWS Greengrass Component SDK into your project
git clone https://github.com/aws-greengrass/aws-greengrass-component-sdk.git

# Build your component
cmake -B build -D CMAKE_BUILD_TYPE=MinSizeRel
make -C build -j$(nproc)

# The binary 'device_controller' is in ./build/
# Upload this binary to S3 for deployment

Prerequisites:

To build the SDK and the component, you will need the following build dependencies:

Install build dependencies:

On Ubuntu/Debian:

sudo apt install build-essential cmake

On Amazon Linux:

sudo yum install gcc-c++ cmake make

Create a CMakeLists.txt file for your component:

cmake_minimum_required(VERSION 3.10)
project(DeviceController CXX)

set(CMAKE_CXX_STANDARD 20)

# Add SDK as subdirectory
add_subdirectory(aws-greengrass-component-sdk)

# Add C++ SDK subdirectory
add_subdirectory(aws-greengrass-component-sdk/cpp)

add_executable(device_controller device_controller.cpp)
target_link_libraries(device_controller gg-sdk++)

Build steps:

# Clone the AWS Greengrass Component SDK into your project
git clone https://github.com/aws-greengrass/aws-greengrass-component-sdk.git

# Build your component
cmake -B build -D CMAKE_BUILD_TYPE=MinSizeRel
make -C build -j$(nproc)

# The binary 'device_controller' will be in ./build/
# Upload this binary to S3 for deployment

{
  "RecipeFormatVersion": "2020-01-25",
  "ComponentName": "com.example.DeviceController",
  "ComponentVersion": "1.0.0",
  "ComponentType": "aws.greengrass.generic",
  "ComponentDescription": "Receives commands from IoT Core and sends telemetry back to cloud",
  "ComponentPublisher": "[Your Company]",
  "ComponentConfiguration": {
    "DefaultConfiguration": {
      "accessControl": {
        "aws.greengrass.ipc.mqttproxy": {
          "com.example.DeviceController:mqttproxy:1": {
            "policyDescription": "Allows access to subscribe to IoT Core topics",
            "operations": [
              "aws.greengrass#SubscribeToIoTCore"
            ],
            "resources": [
              "commands/device1"
            ]
          },
          "com.example.DeviceController:mqttproxy:2": {
            "policyDescription": "Allows access to publish to IoT Core topics",
            "operations": [
              "aws.greengrass#PublishToIoTCore"
            ],
            "resources": [
              "telemetry/device1"
            ]
          }
        }
      }
    }
  },
  "ComponentDependencies": {
    "aws.greengrass.TokenExchangeService": {
      "VersionRequirement": ">=2.0.0",
      "DependencyType": "HARD"
    }
  },
  "Manifests": [
    {
      "Platform": {
        "os": "linux",
        "runtime": "*"
      },
      "Lifecycle": {
        "run": "python3 -u {artifacts:path}/device_controller.py"
      },
      "Artifacts": [
        {
          "Uri": "s3://YOUR-BUCKET/artifacts/com.example.DeviceController/1.0.0/device_controller.py"
        }
      ]
    }
  ]
}

{
  "RecipeFormatVersion": "2020-01-25",
  "ComponentName": "com.example.DeviceController",
  "ComponentVersion": "1.0.0",
  "ComponentType": "aws.greengrass.generic",
  "ComponentDescription": "Receives commands from IoT Core and sends telemetry back to cloud",
  "ComponentPublisher": "[Your Company]",
  "ComponentConfiguration": {
    "DefaultConfiguration": {
      "accessControl": {
        "aws.greengrass.ipc.mqttproxy": {
          "com.example.DeviceController:mqttproxy:1": {
            "policyDescription": "Allows access to subscribe to IoT Core topics",
            "operations": [
              "aws.greengrass#SubscribeToIoTCore"
            ],
            "resources": [
              "commands/device1"
            ]
          },
          "com.example.DeviceController:mqttproxy:2": {
            "policyDescription": "Allows access to publish to IoT Core topics",
            "operations": [
              "aws.greengrass#PublishToIoTCore"
            ],
            "resources": [
              "telemetry/device1"
            ]
          }
        }
      }
    }
  },
  "ComponentDependencies": {
    "aws.greengrass.TokenExchangeService": {
      "VersionRequirement": ">=2.0.0",
      "DependencyType": "HARD"
    }
  },
  "Manifests": [
    {
      "Platform": {
        "os": "linux",
        "runtime": "*"
      },
      "Lifecycle": {
        "run": "java -jar {artifacts:path}/DeviceController.jar"
      },
      "Artifacts": [
        {
          "Uri": "s3://YOUR-BUCKET/artifacts/com.example.DeviceController/1.0.0/DeviceController.jar"
        }
      ]
    }
  ]
}

{
  "RecipeFormatVersion": "2020-01-25",
  "ComponentName": "com.example.DeviceController",
  "ComponentVersion": "1.0.0",
  "ComponentType": "aws.greengrass.generic",
  "ComponentDescription": "Receives commands from IoT Core and sends telemetry back to cloud",
  "ComponentPublisher": "[Your Company]",
  "ComponentConfiguration": {
    "DefaultConfiguration": {
      "accessControl": {
        "aws.greengrass.ipc.mqttproxy": {
          "com.example.DeviceController:mqttproxy:1": {
            "policyDescription": "Allows access to subscribe to command topics from IoT Core",
            "operations": [
              "aws.greengrass#SubscribeToIoTCore"
            ],
            "resources": [
              "commands/device1"
            ]
          },
          "com.example.DeviceController:mqttproxy:2": {
            "policyDescription": "Allows access to publish telemetry to IoT Core",
            "operations": [
              "aws.greengrass#PublishToIoTCore"
            ],
            "resources": [
              "telemetry/*"
            ]
          }
        }
      }
    }
  },
  "Manifests": [
    {
      "Platform": {
        "os": "linux",
        "runtime": "*"
      },
      "Lifecycle": {
        "run": "cd {artifacts:decompressedPath}/DeviceController && node DeviceController.js"
      },
      "Artifacts": [
        {
          "Uri": "s3://YOUR-BUCKET/artifacts/com.example.DeviceController/1.0.0/DeviceController.zip",
          "Unarchive": "ZIP"
        }
      ]
    }
  ]
}

{
  "RecipeFormatVersion": "2020-01-25",
  "ComponentName": "com.example.DeviceController",
  "ComponentVersion": "1.0.0",
  "ComponentType": "aws.greengrass.generic",
  "ComponentDescription": "Receives commands from IoT Core and sends telemetry back to cloud",
  "ComponentPublisher": "[Your Company]",
  "ComponentConfiguration": {
    "DefaultConfiguration": {
      "accessControl": {
        "aws.greengrass.ipc.mqttproxy": {
          "com.example.DeviceController:mqttproxy:1": {
            "policyDescription": "Allows access to subscribe to IoT Core topics",
            "operations": ["aws.greengrass#SubscribeToIoTCore"],
            "resources": ["commands/device1"]
          },
          "com.example.DeviceController:mqttproxy:2": {
            "policyDescription": "Allows access to publish to IoT Core topics",
            "operations": ["aws.greengrass#PublishToIoTCore"],
            "resources": ["telemetry/device1"]
          }
        }
      }
    }
  },
  "Manifests": [
    {
      "Platform": {
        "os": "linux",
        "runtime": "*"
      },
      "Lifecycle": {
        "run": "{artifacts:path}/device_controller"
      },
      "Artifacts": [
        {
          "Uri": "s3://YOUR-BUCKET/artifacts/com.example.DeviceController/1.0.0/device_controller"
        }
      ]
    }
  ]
}