Instrumenting web frameworks deployed to serverless environments

Using the Amazon CLI, create a directory for the application. Then change to the new directory.

mkdir serverless_application
cd serverless_application

Next, create a virtual environment within your new directory. Use the following command to activate it.

# Create our virtual environment
virtualenv serverless_env

# Activate it
source serverless_env/bin/activate

Install X-Ray, Flask, Zappa, and the Requests library to your environment.

# Install X-Ray, Flask, Zappa, and Requests into your environment
pip install aws-xray-sdk flask zappa requests

Add application code to the serverless_application directory. For this example, we can build off of Flasks's Hello World example.

In the serverless_application directory, create a file named my_app.py. Then use a text editor to add the following commands. This application instruments the Requests library, patches the Flask application's middleware, and opens the endpoint '/'.

# Import the X-Ray modules
from aws_xray_sdk.ext.flask.middleware import XRayMiddleware
from aws_xray_sdk.core import patcher, xray_recorder
from flask import Flask
import requests

# Patch the requests module to enable automatic instrumentation
patcher.patch(('requests',))

app = Flask(__name__)

# Configure the X-Ray recorder to generate segments with our service name
xray_recorder.configure(service='My First Serverless App')

# Instrument the Flask application
XRayMiddleware(app, xray_recorder)
 
@app.route('/')
def hello_world():
    resp = requests.get("https://aws.amazon.com")
    return 'Hello, World: %s' % resp.url

Initialize Zappa from within the serverless_application directory. For this example, we used the default settings, but if you have customization preferences, Zappa displays configuration instructions.

zappa init

What do you want to call this environment (default 'dev'): dev
...
What do you want to call your bucket? (default 'zappa-*******'): zappa-*******
...
...
It looks like this is a Flask application.
What's the modular path to your app's function?
This will likely be something like 'your_module.app'.
We discovered: my_app.app
Where is your app's function? (default 'my_app.app'): my_app.app
...
Would you like to deploy this application globally? (default 'n') [y/n/(p)rimary]: n

Enable X-Ray. Open the zappa_settings.json file and verify that it looks similar to the example.

{
    "dev": {
        "app_function": "my_app.app",
        "aws_region": "us-west-2",
        "profile_name": "default",
        "project_name": "serverless-exam",
        "runtime": "python2.7",
        "s3_bucket": "zappa-*********"
    }
}

Add "xray_tracing": true as an entry to the configuration file.

{
    "dev": {
        "app_function": "my_app.app",
        "aws_region": "us-west-2",
        "profile_name": "default",
        "project_name": "serverless-exam",
        "runtime": "python2.7",
        "s3_bucket": "zappa-*********",
        "xray_tracing": true
    }
}

Deploy the application. This automatically configures the API Gateway endpoint and uploads your code to Lambda.

zappa deploy

...
Deploying API Gateway..
Deployment complete!: https://**********.execute-api.us-west-2.amazonaws.com/dev

Sign in to the Amazon Web Services Management Console and open the API Gateway console at https://console.amazonaws.cn/apigateway/.

Find your newly generated API. It should look something like serverless-exam-dev.

Choose Stages.

Choose the name of your deployment stage. The default is dev.

On the Logs/Tracing tab, select the Enable X-Ray Tracing box.

Choose Save Changes.

Access the endpoint in your browser. If you used the example Hello World application, it should display the following.

"Hello, World: https://aws.amazon.com/"

Sign in to the Amazon Web Services Management Console and open the X-Ray console at https://console.amazonaws.cn/xray/home.

View segments generated by API Gateway, the Lambda function, and the Lambda container.

Under the Lambda function segment, view a subsegment named My First Serverless App. It's followed by a second subsegment named https://aws.amazon.com.

During initialization, Lambda might also generate a third subsegment named initialization.