Github user mxm commented on the pull request: https://github.com/apache/flink/pull/925#issuecomment-123213630 In the master, I only serialize the user-defined accumulators but not the Flink accumulators. As of this pull request, the accumulators are always serialized even in local setups. Starting multiple actor systems did not solve the problem because Akka always optimizes message passing in local one VM setups, i.e. it does not serialize objects even across actor systems.
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