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From "Bajaj, Abhinav" <abhinav.ba...@here.com>
Subject Jobsubmission fails in Flink 1.7.1 High Availability mode
Date Fri, 13 Sep 2019 02:29:48 GMT
Hi,

I came across an issue during job submission via Flink Cli Client with Flink 1.7.1 in high
availability mode.

Setup:
Flink version:: 1.7.1
Cluster:: K8s
Mode:: High availability with 2 jobmanagers

CLI Command
./bin/flink run -d -c MyExample /myexample.jar
The CLI runs inside a K8s job and submits the Flink job to the Flink cluster. The K8s job
spec allows it to try 3 times to submit the job.

Result:
2019-09-11 22:32:12.908 [Flink-RestClusterClient-IO-thread-4] level=DEBUG org.apache.flink.runtime.rest.RestClient
 - Sending request of class class org.apache.flink.runtime.rest.messages.job.JobSubmitRequestBody
to job-jm-1.job-jm-svc.job-namespace.svc.cluster.local:8081/v1/jobs
2019-09-11 22:32:14.186 [flink-rest-client-netty-thread-1] level=ERROR org.apache.flink.runtime.rest.RestClient
 - Response was not valid JSON.
org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.JsonMappingException: No content
to map due to end-of-input
at [Source: org.apache.flink.shaded.netty4.io.netty.buffer.ByteBufInputStream@2b88f8bb; line:
1, column: 0]
      at org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:256)
      at org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.ObjectMapper._initForReading(ObjectMapper.java:3851)
      at org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3792)
      at org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.ObjectMapper.readTree(ObjectMapper.java:2272)
      at org.apache.flink.runtime.rest.RestClient$ClientHandler.readRawResponse(RestClient.java:504)
      at org.apache.flink.runtime.rest.RestClient$ClientHandler.channelRead0(RestClient.java:452)
             ………
2019-09-11 22:32:14.186 [flink-rest-client-netty-thread-1] level=ERROR org.apache.flink.runtime.rest.RestClient
 - Unexpected plain-text response:
……..

The job submission fails after exhausting the number of retries.

Observations:
I looked into the debug logs & Flink code to come to below conclusions –

  *   CLI rest client received an empty response body from the jobmanager (job-jm-1). I think
the response was a redirect and the RestClient class does not handle redirects. This explains
the above exception from Jackson and missing response body logged in “org.apache.flink.runtime.rest.RestClient
 - Unexpected plain-text response:” logs above.
  *   The ZooKeeperLeaderRetrievalService in the rest client logs that job-jm-1 became leader
followed by a log that job-jm-0 became leader. The address of job-jm-1 is http and address
of job-jm-0 is akka url. CLI logs at end of email.
  *   The RestClusterClient class does not update the leader during the job submission if
the leader changes.
  *   All the 3 times the CLI K8s job tried to submit the Flink job, ZooKeeperLeaderRetrievalService
finds both the events of job-jm-1 becoming the leader followed by job-jm-0. So all the 3 retries
fails to submit the job with same reason of empty response.
  *   The jobmanager logs from both job-jm-0 and job-jm-1 shows that job-jm-0 is the leader
and job-jm-1 was never a leader. This contradicts the CLI logs.

Open questions:

  *   I am not sure why the CLI’s ZooKeeperLeaderRetrievalService thinks job-jm-1 was the
leader whereas the both jobmanager’s ZooKeeperLeaderRetrievalService considers job-jm-0
as the leader throughout the cluster lifetime.
  *   Even if CLI’s ZooKeeperLeaderRetrievalService thinks leader has changed from job-jm-1
to job-jm-0, it still uses job-jm-1. Is that a known issue with Flink 1.7.1 rest client that
it doesn’t update the leader if it changed?
  *   Why one leader address is http while other is akka url?

Can someone help check and confirm my observations above and help answer the questions?

Highly appreciate your time and help.

~ Abhinav Bajaj


CLI Logs -

2019-09-11 22:30:31.077 [main-EventThread] level=DEBUG o.a.f.r.leaderretrieval.ZooKeeperLeaderRetrievalService
 - Leader node has changed.
2019-09-11 22:30:31.171 [main-EventThread] level=DEBUG o.a.f.r.leaderretrieval.ZooKeeperLeaderRetrievalService
 - New leader information: Leader=http://job-jm-1.job-jm-svc.job-namespace.svc.cluster.local:8081,
session ID=c1422a1b-a6b8-43b0-85d7-87b95af16932.

……
2019-09-11 22:30:31.270 [main-EventThread] level=DEBUG o.a.f.r.leaderretrieval.ZooKeeperLeaderRetrievalService
 - Leader node has changed
2019-09-11 22:30:31.270 [main-EventThread] level=DEBUG o.a.f.r.leaderretrieval.ZooKeeperLeaderRetrievalService
 - New leader information: Leader=akka.tcp://flink@job-jm-0.job-jm-svc.job-namespace.svc.cluster.local:6126/user/dispatcher,
session ID=4e4d03d5-2abe-449c-af2e-df2e0cd80e26



job-jm-0 Logs -
2019-09-11 22:29:59.781 [main-EventThread] level=DEBUG o.a.f.r.leaderretrieval.ZooKeeperLeaderRetrievalService
 - New leader information: Leader=akka.tcp://flink@job-jm-0.job-jm-svc.job-namespace.svc.cluster.local:6126/user/resourcemanager,
session ID=e1f026b1-e368-4524-9fab-2e031423f74f.
2019-09-11 22:29:59.876 [main-EventThread] level=DEBUG o.a.f.r.leaderretrieval.ZooKeeperLeaderRetrievalService
 - New leader information: Leader=akka.tcp://flink@job-jm-0.job-jm-svc.job-namespace.svc.cluster.local:6126/user/dispatcher,
session ID=4e4d03d5-2abe-449c-af2e-df2e0cd80e26.


job-jm-1 Logs -
2019-09-11 22:29:59.889 [main-EventThread] level=DEBUG o.a.f.r.leaderretrieval.ZooKeeperLeaderRetrievalService
 - New leader information: Leader=akka.tcp://flink@job-jm-0.job-jm-svc.job-namespace.svc.cluster.local:6126/user/resourcemanager,
session ID=e1f026b1-e368-4524-9fab-2e031423f74f.
2019-09-11 22:29:59.976 [main-EventThread] level=DEBUG o.a.f.r.leaderretrieval.ZooKeeperLeaderRetrievalService
 - New leader information: Leader=akka.tcp://flink@job-jm-0.job-jm-svc.job-namespace.svc.cluster.local:6126/user/dispatcher,
session ID=4e4d03d5-2abe-449c-af2e-df2e0cd80e26.





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