1. 问题描述
最近做一个针对 Yarn Application 进行错误诊断的需求，需要从 Resource Manager 获取 Application 的运行信息，比如：
GET /ws/v1/cluster/apps/application_1561545353229_936285 HTTP/1.1
Host: yarn.xxx.com
Accept: */*
accept-encoding: gzip, deflate
这个接口使用 Postman 可以得到对应的结果：
{
"app": {
"id": "application_1561545353229_936285",
"user": "bp_growth",
"name": "moses:278648",
"queue": "root.bp_growth_dev",
"state": "FINISHED",
"finalStatus": "FAILED",
"progress": 100,
"trackingUI": "History",
"trackingUrl": "http://yarn-rm02.tc.rack.xxx.com:8088/proxy/application_1561545353229_936285/",
"diagnostics": "Task failed task_1561545353229_936285_m_000008\nJob failed as tasks failed. failedMaps:1 failedReduces:0\n",
"clusterId": 1561545353229,
"applicationType": "MAPREDUCE",
"applicationTags": "",
"startedTime": 1562740151124,
"finishedTime": 1562740195218,
"elapsedTime": 44094,
"amContainerLogs": "http://data1117.tc.rack.xxx.com:8042/node/containerlogs/container_e93_1561545353229_936285_01_000001/bp_growth",
"amHostHttpAddress": "data1117.tc.rack.xxx.com:8042",
"allocatedMB": -1,
"allocatedVCores": -1,
"reservedMB": -1,
"reservedVCores": -1,
"runningContainers": -1,
"memorySeconds": 1583688,
"vcoreSeconds": 721,
"preemptedResourceMB": 0,
"preemptedResourceVCores": 0,
"numNonAMContainerPreempted": 0,
"numAMContainerPreempted": 0,
"logAggregationStatus": "TIME_OUT"
}
}
但是使用 RestTemplate 去请求的时候却会得到异常：
org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Illegal character ((CTRL-CHAR, code 31)): only regular white space (\r, \n, \t) is allowed between tokens; nested exception is com.fasterxml.jackson.core.JsonParseException: Illegal character ((CTRL-CHAR, code 31)): only regular white space (\r, \n, \t) is allowed between tokens
at [Source: (PushbackInputStream); line: 1, column: 2]
原因是 Response 的结果使用了 Gzip 进行压缩。
2. 解决方案
在网上找到的最简单的解决方案来自：How to parse gzip encoded response with RestTemplate from Spring-Web。
简单来说就是在构造 RestTemplate 的时候指定 ClientHttpRequestFactory。
Maven 项目引入一个依赖：
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
</dependency>
由于我同时使用了 SpringBoot，所以不需要指定版本。
public void test() {
HttpComponentsClientHttpRequestFactory clientHttpRequestFactory = new HttpComponentsClientHttpRequestFactory(
HttpClientBuilder.create().build());
RestTemplate restTemplate = new RestTemplate(clientHttpRequestFactory);
Map forObject = restTemplate.getForObject("http://yarn.xxx.com/ws/v1/cluster/apps/application_1561545353229_936285", Map.class);
System.out.println("forObject = " + forObject);
}