Hi Till, Thanks for the reply. I don’t use batch, so I assume what I am seeing is streaming related. I thought rocksdb writes to a different dir though ( as defined by checkpoint.data.uri)? Regards, Anand
From: Till Rohrmann [mailto:trohrm...@apache.org] Sent: 08 October 2018 13:39 To: Kostas Kloudas Cc: Gopinath, Anand; user; Till Rohrmann Subject: Re: flink memory management / temp-io dir question Hi Anand, spilling using the io directories is only relevant for Flink's batch processing. This happens, for example if you enable blocking data exchange where the produced data cannot be kept in memory. Moreover, it is used by many of Flink's out-of-core data structures to enable exactly this feature (e.g. users are the MutableHashTable, the MergeIterator to combine sorted ata which has been spilled or the SorterMerger to actually spill data). In streaming Flink uses the RocksDB state backend to spill very large state gracefully to disk. Thus, you would need to configure RocksDB in order to control the spilling behaviour. Cheers, Till On Mon, Oct 8, 2018 at 2:18 PM Kostas Kloudas <k.klou...@data-artisans.com<mailto:k.klou...@data-artisans.com>> wrote: Sorry, I forgot to cc’ Till. On Oct 8, 2018, at 2:17 PM, Kostas Kloudas <k.klou...@data-artisans.com<mailto:k.klou...@data-artisans.com>> wrote: Hi Anand, I think that Till is the best person to answer your question. Cheers, Kostas On Oct 5, 2018, at 3:44 PM, anand.gopin...@ubs.com<mailto:anand.gopin...@ubs.com> wrote: 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 Visit our website at http://www.ubs.com<http://www.ubs.com/> This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. E-mails are not encrypted and cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. 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