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https://issues.apache.org/jira/browse/FLINK-15032?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16988778#comment-16988778
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Till Rohrmann commented on FLINK-15032:
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Thanks for opening this issue [~maguowei]. The main reason why eager
serialization was introduced was to check if we are exceeding the maximum
framesize of Akka. If that's the case, then we fail with an explicit message
instead of dropping the message and logging a message as Akka does. There was
also the idea to offload large messages to the {{BlobService}} in order to
transmit large messages.
If we are able to maintain these properties while postponing the serialization,
then I'm fine with the proposal. But I would need a bit more details on how we
will achieve this.
> Remove the eager serialization from `RemoteRpcInvocation`
> ----------------------------------------------------------
>
> Key: FLINK-15032
> URL: https://issues.apache.org/jira/browse/FLINK-15032
> Project: Flink
> Issue Type: Improvement
> Components: Runtime / Coordination
> Reporter: Guowei Ma
> Priority: Major
>
> Currently, the constructor of `RemoteRpcInvocation` serializes the
> `parameterTypes` and `arg` of an RPC call. This could lead to a problem:
> Consider a job that has 1k parallelism and has a 1m union list state. When
> deploying the 1k tasks, the eager serialization would use 1G memory
> instantly(Some time the serialization amplifies the memory usage). However,
> the serialized object is only used when the Akka sends the message. So we
> could reduce the memory pressure if we only serialize the object when the
> message would be sent by the Akka.
> Akka would serialize the message at last and all the XXXGateway related class
> could be visible by the RPC level. Because of that, I think the eager
> serialization in the constructor of `RemoteRpcInvocation` could be avoided. I
> also do a simple test and find this could reduce the time cost of the RPC
> call. The 1k number of RPC calls with 1m `String` message: The current
> version costs around 2700ms; the Nonserialization version cost about 37ms.
>
> In summary, this Jira proposes to remove the eager serialization at the
> constructor of `RemoteRpcInvocation`.
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