I had a quick look at it, and we could do that, even for RocksDB: the method does a meta data lookup similar to what state registration does, remove the meta data and drop the column family. But until then, there is currently no complete dropping a keyed state.
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> Am 22.02.2018 um 12:19 schrieb Stefan Richter <s.rich...@data-artisans.com>: > > Right now, I don’t think there is a way of doing that. I don’t think there is > something fundament against having a method that drops a state complete, data > and registered meta data. But so far that never existed and it seems nobody > ever needed it (or asked for it at least). The closest thing for keyed state > is calling the „clear()“ method, but the meta data will stick. > >> Am 22.02.2018 um 12:06 schrieb Gyula Fóra <gyula.f...@gmail.com>: >> >> Do you have any suggestion how to completely delete an operator and keyed >> state? >> For operator state this seems to be easy enough, but what about completely >> dropping a keyed state? >> >> Gyula >> >> Stefan Richter <s.rich...@data-artisans.com> ezt írta (időpont: 2018. febr. >> 22., Cs, 11:46): >> >>> >>> Hi, >>> >>> I don’t think that this is a bug, but rather a necessity that comes with >>> the (imo questionable) design of allowing lazy state registration. In this >>> design, just because a state is *currently* not registered does not mean >>> that you can simply drop it. Imagine that your code did *not yet* >>> re-register a state, but could still do so in the future. If a >>> checkpoint/recovery happens in between, all data for that state would >>> suddenly be lost, just because by chance the state was not registered „fast >>> enough“. As I see it, the proper way is the register the state under the >>> same name and clear it if you want to get rid of the data. There is >>> currently no call that explicitly drops a state that was once declared, and >>> you might make a case that this is a feature to have for the future. Then >>> again, we need a general decision about lazy and eager state IMO. >>> >>> Best, >>> Stefan >>> >>>> Am 22.02.2018 um 11:10 schrieb Gyula Fóra <gyula.f...@gmail.com>: >>>> >>>> Hi all, >>>> >>>> We have discovered a fairly serious memory leak >>>> in DefaultOperatorStateBackend, with broadcast (union) list states. >>>> >>>> The problem seems to occur when a broadcast state name is changed, in >>> order >>>> to drop some state (intentionally). >>>> >>>> Flink does not drop the "garbage" broadcast state, and keeps >>> snapshotting, >>>> broadcasting, multiplying it exponentially at every savepoint/restore >>> cycle. >>>> >>>> With high enough parallelism this can easily lead to small states (few >>>> bytes) growing to several gigs and more over a few restarts eventually >>>> leading to a very bad crash restart cycle where TMs OOM in a few secs. >>>> >>>> Basically 2 things seems to be missing, garbage collection of >>> unreferenced >>>> operator states (they are eagerly restored into memory). And probably >>> lazy >>>> restore would also be nice :) >>>> >>>> We run Flink 1.4.0 but 1.4.1 seems to be affected as well, haven't >>> checked >>>> the latest master. >>>> >>>> Could someone please confirm that this behaviour is not as intended? >>>> >>>> Cheers, >>>> Gyula >>> >>> >
