2

We started with the implementation of a camunda based workflow solution. In the moment the setup is like this:

  1. A spring boot application with an embedded camunda BPM (via camunda-bpm-spring-boot-starter-rest and camunda-bpm-spring-boot-starter-webapp)
  2. A spring boot application with an external task client (via camunda-external-task-client)

Everything is working fine so far. Our workflow is running and the external client is doing his job... But after a while (when there is nothing to do for the external client) is see an exception in the log of the external task client:

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)

What could be the reason for this? Maybe Configuration error in server or client? One remark: The execution of the external task is slow (like 10-30 seconds)

Update: I created a complete example: https://c.gmx.net/@505442085592110443/BIItJGdwTcuWwk7_XqNOXw

To create the error scenario you have to:

  1. Start the ExampleApplication inside the spring-boot project
  2. Start the ExternalClientApp inside the Spring-Boot-Client project
  3. Wait a few minutes

the log output of the external client should look like this:

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
Improve this question
5
  • Is this a transient exception? The error you're seeing indicates that the application server itself - in this case the embedded Tomcat application server in Spring Boot - isn't responding to HTTP requests, at least for some short period of time. Commented Jun 7, 2019 at 16:15
  • i included a complete example Commented Jun 11, 2019 at 9:24
  • Is this a reliable test case? In other words, will you consistently see this exception after a few minutes every time? Another, very important question: When you see this exception, are you able to connect via the out-of-the-box REST API directly into Camunda BPM? Commented Jun 12, 2019 at 15:39
  • i see it every time. the external client is still working and gets new jobs. the only problem is repeated exception in the logs, when there is nothing todo Commented Jun 13, 2019 at 12:43
  • This sounds like a bug in the External Task Client. Perhaps you should report the bug and send along your test zip file to Camunda? You can report it here: app.camunda.com/jira/browse/CAM Commented Jun 17, 2019 at 23:09

1 Answer 1

Reset to default
0

After testing it on different machines/jdk/OS it looks like the problem is only on windows 7 machines.

i think the error reason is described here: Apache HttpClient Interim Error: NoHttpResponseException

so the server is killing the http session because it has not been used for a longer time!

my workaround is to configure a different backup strategy in the client and so far i have no errors anymore:

tldr: i think it is a bug in the external client that only happens on Win7 but i found a workaround:

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

PS i reported it as a bug: https://app.camunda.com/jira/browse/CAM-10526

Improve this answer
Sign up to request clarification or add additional context in comments.

Comments

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.