Details
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Sub-task
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Status: Open
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Minor
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Resolution: Unresolved
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1.9.0
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None
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None
Description
Hi, all,
Previously I'm testing HighAvailabilityService of Flink 1.9 on k8s. When testing Flink session cluster with 3 JM pods deployed on k8s, I find the jar I previously uploaded to the web frontend will continuously dispear in "Uploaded Jars" web page. As a result, it's hard to submit the job.
After investigation, I find that it has something to do with (1) the implementation of method "handleRequest" of "JarListHandler" and "JarUploadHandler" RestHandlers along with (2) the routing mechanism of k8s service.
(1) It seem to me that "handleRequest" method should dispatch the message through "DispatcherGateway gateway" to the leader JM. While the two RestHanders don't use the gateway and just do things locally. That is to say if a "upload jar" request or "list loaded jars" request is sent to any of the 3 JMs, the web frontend will only storage or fetch jars from local directory.
(2) I use k8s service to open a flink web page, the URL pattern is (PS: start "kubectl proxy" locally): http://127.0.0.1:8001/api/v1/namespaces/${my_ns}/services/${my_session_cluster_service}:ui/proxy/#/submit
Since there a 3 endpoints (3 JMs) of this k8s service, the k8s routing mechanism will randomly choose which endpoint (JM) a REST message sends to.
As a result of the two factors, Flink session cluster previously cannot be deployed with multiple JMs using HighAvailablityService on k8s.
Proposals:
(1) redirect jar related REST messages to the leader JM
(2) (along with proposal(1)) synchronize jar files with the standby JMs incase of standby JM taking the leadership
(3) support upload jars to global filesystem (etc. dfs)
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