Tracing calls to downstream HTTP web services with the X-Ray SDK for Java - Amazon X-Ray
Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Tracing calls to downstream HTTP web services with the X-Ray SDK for Java

When your application makes calls to microservices or public HTTP APIs, you can use the X-Ray SDK for Java's version of HttpClient to instrument those calls and add the API to the service graph as a downstream service.

The X-Ray SDK for Java includes DefaultHttpClient and HttpClientBuilder classes that can be used in place of the Apache HttpComponents equivalents to instrument outgoing HTTP calls.

  • com.amazonaws.xray.proxies.apache.http.DefaultHttpClient - org.apache.http.impl.client.DefaultHttpClient

  • com.amazonaws.xray.proxies.apache.http.HttpClientBuilder - org.apache.http.impl.client.HttpClientBuilder

These libraries are in the aws-xray-recorder-sdk-apache-http submodule.

You can replace your existing import statements with the X-Ray equivalent to instrument all clients, or use the fully qualified name when you initialize a client to instrument specific clients.

Example HttpClientBuilder
import com.fasterxml.jackson.databind.ObjectMapper; import org.apache.http.HttpEntity; import org.apache.http.client.methods.CloseableHttpResponse; import org.apache.http.client.methods.HttpGet; import org.apache.http.impl.client.CloseableHttpClient; import org.apache.http.util.EntityUtils; import com.amazonaws.xray.proxies.apache.http.HttpClientBuilder; ... public String randomName() throws IOException { CloseableHttpClient httpclient = HttpClientBuilder.create().build(); HttpGet httpGet = new HttpGet(""); CloseableHttpResponse response = httpclient.execute(httpGet); try { HttpEntity entity = response.getEntity(); InputStream inputStream = entity.getContent(); ObjectMapper mapper = new ObjectMapper(); Map<String, String> jsonMap = mapper.readValue(inputStream, Map.class); String name = jsonMap.get("name"); EntityUtils.consume(entity); return name; } finally { response.close(); } }

When you instrument a call to a downstream web api, the X-Ray SDK for Java records a subsegment with information about the HTTP request and response. X-Ray uses the subsegment to generate an inferred segment for the remote API.

Example Subsegment for a downstream HTTP call
{ "id": "004f72be19cddc2a", "start_time": 1484786387.131, "end_time": 1484786387.501, "name": "", "namespace": "remote", "http": { "request": { "method": "GET", "url": "" }, "response": { "content_length": -1, "status": 200 } } }
Example Inferred segment for a downstream HTTP call
{ "id": "168416dc2ea97781", "name": "", "trace_id": "1-62be1272-1b71c4274f39f122afa64eab", "start_time": 1484786387.131, "end_time": 1484786387.501, "parent_id": "004f72be19cddc2a", "http": { "request": { "method": "GET", "url": "" }, "response": { "content_length": -1, "status": 200 } }, "inferred": true }