AWS X-Ray
Developer Guide

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("http://names.example.com/api/"); 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": "names.example.com", "namespace": "remote", "http": { "request": { "method": "GET", "url": "https://names.example.com/" }, "response": { "content_length": -1, "status": 200 } } }

Example Inferred Segment for a Downstream HTTP Call

{ "id": "168416dc2ea97781", "name": "names.example.com", "trace_id": "1-5880168b-fd5153bb58284b67678aa78c", "start_time": 1484786387.131, "end_time": 1484786387.501, "parent_id": "004f72be19cddc2a", "http": { "request": { "method": "GET", "url": "https://names.example.com/" }, "response": { "content_length": -1, "status": 200 } }, "inferred": true }