Zhou Parker created FLINK-21289:
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Summary: Application mode on kubernetes deployment support run
PackagedProgram.main with pipeline.classpaths
Key: FLINK-21289
URL: https://issues.apache.org/jira/browse/FLINK-21289
Project: Flink
Issue Type: Improvement
Components: Client / Job Submission, Deployment / Kubernetes
Affects Versions: 1.12.1, 1.11.2
Environment: flink: 1.11
kubernetes: 1.15
Reporter: Zhou Parker
Attachments: 0001-IMP.patch
我尝试将flink作业以application
mode方式提交到kubernetes上运行。但程序的依赖包并不完全存在于local:///opt/flink/usrlib/xxxx.jar中。导致找不到类。
在yarn上可以工作，是因为我们用 {color:#FF0000}-C [http://xxxx|http://xxxx/]
{color}的方式，让依赖可以被URLClassloader加载。
但我发现，当实验提交到kubernetes时，-C只会在 configmap/flink-conf.yaml 中生成一个pipeline.classpaths
配置条目。我们的main函数可以执行，但是在加载外部依赖类的时候提示找不到类。
通过阅读源码，*我发现运行用户代码的类加载器实际并把 pipeline.classpaths
中的条目加入候选URL*，这导致了无法加载类的情况。从源码中，我也发现，可以通过将依赖包放在usrlib目录下（默认的userClassPath）可以解决问题。但我们的依赖可能是动态的，不合适一次性打到镜像里面。
我提议可以改进这个过程，将pipeline.classpaths也加入到对应的类加载器。这个改动很小，我自己经过测试，可以完美解决问题。
I'm trying to submit flink job to kubernetes cluster with application mode, but
throw ClassNotFoundException when dependency class is not shipped in kind of
local:///opt/flink/usrlib/xxxx.jar.
This works on yarn, since we use {color:#FF0000}-C http://xxxx{color} command
line style that let dependency class can be load by URLClassloader.
But i figure out that not works on kubernetes. When submit to kubernetes
cluster, -C is only shipped as item "pipeline.classpaths" in
configmap/flink-conf.yaml。
After read the source code, *i find out that the Classloader launching the
"main" entry of user code without consider add pipeline.classpaths into
candidates URLs*. from source code, i also learn that we can ship the
dependency jar in the usrlib dir to solve the problem. But failed for me, we
are not _preferred_ to ship dependencies in image at compile time, since they
are known dynamically in runtime
I proposed improving the process, let the Classloader consider usrlib as well
as pipeline.classpaths, this is a quite little change. I test the solution and
it works quite well
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