Camunda外部客户端：TASK / CLIENT-02002建立请求连接时发生异常

Question

我们从实施基于camunda的工作流解决方案开始。 目前的设置是这样的：

1. 带有嵌入式camunda BPM的spring boot应用程序（通过camunda-bpm-spring-boot-starter-rest和camunda-bpm-spring-boot-starter-webapp）
2. 一个带有外部任务客户端的Spring Boot应用程序（通过camunda-external-task-client）

到目前为止一切正常。 我们的工作流正在运行，外部客户端正在执行其工作...但是一段时间（当外部客户端无需执行任何操作时）在外部任务客户端的日志中看到异常：

15:49:09.692 [E] [TopicSubscripti] client.logError:70 - TASK/CLIENT-03001 Exception while fetch and lock task.
org.camunda.bpm.client.impl.EngineClientException: TASK/CLIENT-02002 Exception while establishing connection for request 'POST http://localhost:8080/enrichmentservice/api/rest/1.0/rest/external-task/fetchAndLock HTTP/1.1'
at org.camunda.bpm.client.impl.EngineClientLogger.exceptionWhileEstablishingConnection(EngineClientLogger.java:36)
at org.camunda.bpm.client.impl.RequestExecutor.executeRequest(RequestExecutor.java:101)
at org.camunda.bpm.client.impl.RequestExecutor.postRequest(RequestExecutor.java:74)
at org.camunda.bpm.client.impl.EngineClient.fetchAndLock(EngineClient.java:72)
at org.camunda.bpm.client.topic.impl.TopicSubscriptionManager.fetchAndLock(TopicSubscriptionManager.java:135)
at org.camunda.bpm.client.topic.impl.TopicSubscriptionManager.acquire(TopicSubscriptionManager.java:101)
at org.camunda.bpm.client.topic.impl.TopicSubscriptionManager.run(TopicSubscriptionManager.java:87)
at java.lang.Thread.run(Thread.java:748)
Caused by: org.apache.http.NoHttpResponseException: localhost:8080 failed to respond
at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:141)
at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:56)
at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:259)
at org.apache.http.impl.DefaultBHttpClientConnection.receiveResponseHeader(DefaultBHttpClientConnection.java:163)
at org.apache.http.impl.conn.CPoolProxy.receiveResponseHeader(CPoolProxy.java:165)
at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:273)
at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:125)
at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:272)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:185)
at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:72)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:221)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:165)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:140)
at org.camunda.bpm.client.impl.RequestExecutor.executeRequest(RequestExecutor.java:88)
at org.camunda.bpm.client.impl.RequestExecutor.postRequest(RequestExecutor.java:74)
at org.camunda.bpm.client.impl.EngineClient.fetchAndLock(EngineClient.java:72)
at org.camunda.bpm.client.topic.impl.TopicSubscriptionManager.fetchAndLock(TopicSubscriptionManager.java:135)

这可能是什么原因？ 也许服务器或客户端中的配置错误？ 备注：外部任务的执行速度很慢（例如10到30秒）

更新：我创建了一个完整的示例： https : //c.gmx.net/@505442085592110443/BIItJGdwTcuWwk7_XqNOXw

要创建错误方案，您必须：

1. 在spring-boot项目中启动ExampleApplication
2. 在Spring-Boot-Client项目中启动ExternalClientApp
3. 等一下

外部客户端的日志输出应如下所示：

Subscribe client for: approveLoan
Subscription done
Subscribe client for: waitTask
Subscription done
pojo before: ObjectValue [value=ExamplePojo [num=123, textVal=some text], isDeserialized=true, serializationDataFormat=application/x-java-serialized-object, objectTypeName=org.camunda.bpm.example.tasks.ExamplePojo, serializedValue=156 chars, isTransient=false]
pojo changed: ObjectValue [value=ExamplePojo [num=123, textVal=external changed], isDeserialized=true, serializationDataFormat=application/x-java-serialized-object, objectTypeName=org.camunda.bpm.example.tasks.ExamplePojo, serializedValue=156 chars, isTransient=false]
The External Task 28 has been completed!
The External Task 32 has been completed! (done = false)
The External Task 39 has been completed! (done = false)
The External Task 46 has been completed! (done = true)
149038 [TopicSubscriptionManager] ERROR org.camunda.bpm.client - TASK/CLIENT-03001 Exception while fetch and lock task.
org.camunda.bpm.client.impl.EngineClientException: TASK/CLIENT-02002 Exception while establishing connection for request 'POST http://localhost:8080/rest/external-task/fetchAndLock HTTP/1.1'
at org.camunda.bpm.client.impl.EngineClientLogger.exceptionWhileEstablishingConnection(EngineClientLogger.java:36)
at org.camunda.bpm.client.impl.RequestExecutor.executeRequest(RequestExecutor.java:101)
at org.camunda.bpm.client.impl.RequestExecutor.postRequest(RequestExecutor.java:74)
at org.camunda.bpm.client.impl.EngineClient.fetchAndLock(EngineClient.java:72)
at org.camunda.bpm.client.topic.impl.TopicSubscriptionManager.fetchAndLock(TopicSubscriptionManager.java:135)
at org.camunda.bpm.client.topic.impl.TopicSubscriptionManager.acquire(TopicSubscriptionManager.java:101)
at org.camunda.bpm.client.topic.impl.TopicSubscriptionManager.run(TopicSubscriptionManager.java:87)
at java.lang.Thread.run(Thread.java:748)
Caused by: org.apache.http.NoHttpResponseException: localhost:8080 failed to respond
at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:141)
at org.apache.http.impl.conn.DefaultHttpResponseParser.parseHead(DefaultHttpResponseParser.java:56)
at org.apache.http.impl.io.AbstractMessageParser.parse(AbstractMessageParser.java:259)
at org.apache.http.impl.DefaultBHttpClientConnection.receiveResponseHeader(DefaultBHttpClientConnection.java:163)
at org.apache.http.impl.conn.CPoolProxy.receiveResponseHeader(CPoolProxy.java:157)
at org.apache.http.protocol.HttpRequestExecutor.doReceiveResponse(HttpRequestExecutor.java:273)
at org.apache.http.protocol.HttpRequestExecutor.execute(HttpRequestExecutor.java:125)
at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:272)
at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:185)
at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:89)
at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:110)
at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:185)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:72)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:221)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:165)
at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:140)
at org.camunda.bpm.client.impl.RequestExecutor.executeRequest(RequestExecutor.java:88)
... 6 more

Answer 1

在不同的机器/ jdk / OS上对其进行测试后，问题似乎仅出现在Windows 7机器上。

我认为错误原因描述如下： Apache HttpClient临时错误：NoHttpResponseException

因此服务器正在终止http会话，因为它已经使用了很长时间了！

我的解决方法是在客户端中配置其他备份策略，到目前为止，我没有任何错误了：

tldr：我认为这是仅在Win7上发生的外部客户端错误，但我找到了解决方法：

    ExternalTaskClient client = ExternalTaskClient.create().baseUrl(baseUrl).backoffStrategy(new ExponentialBackoffStrategy(500L, 2, 30000L)).
            build();

PS我报告它是一个错误： https : //app.camunda.com/jira/browse/CAM-10526