Hi Enrico, I have rebased https://github.com/apache/pulsar/pull/9292 PR again after you helped to dismiss the blocker. Can you please help to review it again as you were part of the PR reviewer earlier.
I think below two PRs were the most critical one to scale the unack message path because earlier guava-Range data-structure was forcing broker to load millions of objects in memory which causing high memory-pressure and large gc-pauses which was making impossible to scale large number of unack messages into the system. But below PRs made it possible to scale unack messages paths in the broker and PR#9292 was built by extending the same vision of below PRs but somehow it got delayed. https://github.com/apache/pulsar/pull/3818 https://github.com/apache/pulsar/pull/3819 Thanks, Rajan On Mon, Sep 23, 2024 at 6:59 PM Rajan Dhabalia <rdhaba...@apache.org> wrote: > >> I am sorry I haven't followed up andI am not able to spend much time. I > don't want to block your proposal Rajan. > > I totally understand and I am sure it was not intentional by you to block > this PR. > > However, there are multiple other PRs related to key-shared sub, stats, > cursor performance, and other PRs are still blocked by others and people > just block it because they think they don't have this usecase. It's so > unfortunate that people easily merge implementations which only handle > small-scale usecases but the usecases for which Pulsar was built are > being blocked or take a long time to merge. It's just that I don't have > that energy to keep following up for useful and important changes for > Pulsar. And this is one of these examples as well. I have also started > discussion about improving the PIP process because it has become painful in > many cases. > > Thanks, > Rajan > > > On Sat, Sep 21, 2024 at 4:18 AM Enrico Olivelli <eolive...@gmail.com> > wrote: > >> Il Sab 21 Set 2024, 01:51 Rajan Dhabalia <rdhaba...@apache.org> ha >> scritto: >> >> > Hi Andrey, >> > >> > Thanks for submitting the PR as we have been facing this issue for a >> long >> > time now and we also have PR which solves this issue in a simple and a >> > fundamental way with proven perf results as well. >> > >> > PR: https://github.com/apache/pulsar/pull/9292 >> > >> > But again I am not sure some folks blocked this PR without saying the >> > reason even after asking multiple times and PR progress has been blocked >> > since then , and it could be a good time to revive it and try to find >> the >> > right solution to address this issue. >> > >> >> I have dismissed my review. >> I am sorry I haven't followed up andI am not able to spend much time. I >> don't want to block your proposal Rajan. >> >> The other Request Changes review was from Sijie, I don't know if he wants >> to dismiss his own review and let the community restart the discussion. >> >> I support both of the proposals. >> I had worked with Andrey for this PIP and we saw it solving a problem for >> one usecase with millions of holes in the sequence of acks. >> >> Let's solve this problem >> >> Enrico >> >> >> >> > Thanks, >> > Rajan >> > >> > On Fri, Sep 20, 2024 at 4:40 PM Andrey Yegorov <ayego...@apache.org> >> > wrote: >> > >> > > Hello, >> > > >> > > I created a PIP for handling large PositionInfo state (large number of >> > > unacked ranges in cursor.) >> > > >> > > PIP PR: https://github.com/apache/pulsar/pull/23328 >> > > Proposed implementation: https://github.com/apache/pulsar/pull/22799 >> > > >> > > Relevant excerpts from PIP: >> > > ----------- >> > > Background knowledge >> > > < >> > > >> > >> https://github.com/apache/pulsar/blob/124255a82d145160d6d729a6aebd6aad47fa051e/pip/pip-381-large-positioninfo.md#background-knowledge >> > > > >> > > >> > > In case of KEY_SHARED subscription and out-of-order acknowledgments, >> the >> > > PositionInfo state can be persisted to preserve the state, with >> > > configurable maximum number of ranges to persist: >> > > >> > > # Max number of "acknowledgment holes" that are going to be >> persistently >> > > stored. >> > > # When acknowledging out of order, a consumer will leave holes that >> are >> > > supposed >> > > # to be quickly filled by acking all the messages. The information of >> > which >> > > # messages are acknowledged is persisted by compressing in "ranges" of >> > > messages >> > > # that were acknowledged. After the max number of ranges is reached, >> > > the information >> > > # will only be tracked in memory and messages will be redelivered in >> case >> > > of >> > > # crashes. >> > > managedLedgerMaxUnackedRangesToPersist=10000 >> > > >> > > The PositionInfo state is stored to the BookKeeper as a single entry, >> and >> > > it can grow large if the number of ranges is large. Currently, this >> means >> > > that BookKeeper can fail persisting too large PositionInfo state, e.g. >> > over >> > > 1MB by default and the ManagedCursor recovery on topic reload might >> not >> > > succeed. >> > > Motivation >> > > >> > > While keeping the number of ranges low to prevent such problems is a >> > common >> > > sense solution, there are cases where the higher number of ranges is >> > > required. For example, in case of the JMS protocol handler, JMS >> consumers >> > > with filters may end up processing data out of order and/or at >> different >> > > speed, and the number of ranges can grow large. >> > > Goals >> > > < >> > > >> > >> https://github.com/apache/pulsar/blob/124255a82d145160d6d729a6aebd6aad47fa051e/pip/pip-381-large-positioninfo.md#goals >> > > > >> > > >> > > Store the PositionInfo state in a BookKeeper ledger as multiple >> entries >> > if >> > > the state grows too large to be stored as a single entry. >> > > In Scope >> > > < >> > > >> > >> https://github.com/apache/pulsar/blob/124255a82d145160d6d729a6aebd6aad47fa051e/pip/pip-381-large-positioninfo.md#in-scope >> > > > >> > > >> > > Transparent backwards compatibility if the PositionInfo state is small >> > > enough. >> > > Out of Scope >> > > < >> > > >> > >> https://github.com/apache/pulsar/blob/124255a82d145160d6d729a6aebd6aad47fa051e/pip/pip-381-large-positioninfo.md#out-of-scope >> > > > >> > > >> > > Backwards compatibility in case of the PositionInfo state is too >> large to >> > > be stored as a single entry. >> > > High Level Design >> > > < >> > > >> > >> https://github.com/apache/pulsar/blob/124255a82d145160d6d729a6aebd6aad47fa051e/pip/pip-381-large-positioninfo.md#high-level-design >> > > > >> > > >> > > Cursor state writes and reads are happening at the same cases as >> > currently, >> > > without changes. >> > > >> > > Write path: >> > > >> > > 1. serialize the PositionInfo state to a byte array. >> > > 2. if the byte array is smaller than the threshold, store it as a >> > single >> > > entry, as now. Done. >> > > 3. if the byte array is larger than the threshold, split it to >> smaller >> > > chunks and store the chunks in a BookKeeper ledger. >> > > 4. write the "footer" into the metadata store as a last entry. >> > > >> > > See persistPositionToLedger() in ManagedCursorImpl for the >> > implementation. >> > > >> > > The footer is a JSON representation of >> > > >> > > public static final class ChunkSequenceFooter { >> > > private int numParts; >> > > private int length; >> > > } >> > > >> > > >> > > Read path: >> > > >> > > 1. read the last entry from the metadata store. >> > > 2. if the entry does not appear to be a JSON, treat it as >> serialized >> > > PositionInfo state and use it as is. Done. >> > > 3. if the footer is a JSON, parse number of chunks and length from >> the >> > > json. >> > > 4. read the chunks from the BookKeeper ledger (entries from >> startPos = >> > > footerPosition - chunkSequenceFooter.numParts to footerPosition - >> 1) >> > and >> > > merge them. >> > > 5. parse the merged byte array as a PositionInfo state. >> > > >> > > See recoverFromLedgerByEntryId() in ManagedCursorImpl for the >> > > implementation. >> > > >> > > --- >> > > Andrey >> > > >> > >> >
