Hi , I had a question with respect flink memory management / overspill to /tmp.
In the docs (https://ci.apache.org/projects/flink/flink-docs-release-1.6/ops/config.html#configuring-temporary-io-directories) it says: Although Flink aims to process as much data in main memory as possible, it is not uncommon that more data needs to be processed than memory is available. Flink's runtime is designed to write temporary data to disk to handle these situations.... In a flink job that processes a couple streams of 1M events in a windowed co group function with parallelism 8 - we see 8 dirs created in /tmp with 100s of Meg of data, the name of each dir seems aligned to the data for each parallel thread windowing against the co-group operator e.g. bash-4.2$ du -sh * 0 flink-dist-cache-a4a69215-665a-4c3c-8d90-416cbe192f26 352M flink-io-9033517c-ac92-4baa-9e59-79bc80c72a9e 4.0K localState 7.2M rocksdb-lib-03d9460b15e6bf6af4f3d9b0ff7980c3 bash-4.2$ du -sh flink-io-9033517c-ac92-4baa-9e59-79bc80c72a9e/* ... 36M flink-io-9033517c-ac92-4baa-9e59-79bc80c72a9e/job_cf2dca7843dd6b6296aa1a9d15a1d435_op_WindowOperator_014556c228cb5344d41861769d2bbbc1__1_8__uuid_93307150-4f62-4b06-a71e-0230360f7d86 36M flink-io-9033517c-ac92-4baa-9e59-79bc80c72a9e/job_cf2dca7843dd6b6296aa1a9d15a1d435_op_WindowOperator_014556c228cb5344d41861769d2bbbc1__2_8__uuid_7b2f8957-7044-4bb3-869e-28843bd737a1 36M flink-io-9033517c-ac92-4baa-9e59-79bc80c72a9e/job_cf2dca7843dd6b6296aa1a9d15a1d435_op_WindowOperator_014556c228cb5344d41861769d2bbbc1__3_8__uuid_54306a44-7e06-45ae-ba0e-4649887bca7e ... I was wondering can / should this 'over spill' be avoided by increasing the heap of the task manager or another config or should I not worry about it? Is there more information/docs on how this data is used/ cleaned up & what is the cost of this overspill to latency/ checkpointing? Any impact I should be aware of? thanks Anand
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