Full_Name: Howard Chu Version: 2.4 OS: URL: ftp://ftp.openldap.org/incoming/ Submission from: (NULL) (70.87.222.79) Submitted by: hyc Long-lived read transactions prevent old pages from being reused in LMDB. We've seen a situation triggered by the syncprov overlay that aggravates this problem - a consumer connects and performs a syncrepl refresh. Its sync cookie is too old for the syncprov sessionlog to be used, so syncprov must generate a presentlist of all of the entryUUIDs in the database. This is a very long search (in this case, around 1.5 million objects) and writes are continuing while this happens. Also, there are multiple consumers repeating this at staggered times (due to the situation described in ITS#8225 they all tend to reconnect at closely situated times). Because of these long read transactions the incoming writes are forced to use new database pages, and so the DB file size grows drastically during these refreshes. This specific case for syncprov can be mitigated by using a much larger syncprov sessionlog (and in the future, by enhancing syncprov to use accesslog), but there are many other instances when clients may legitimately issue searches that span the entire database. The fix from ITS#7904 should be extended to release and reacquire the read transaction every N entries to make large searches friendlier to write traffic. The default value of N probably should not be zero, but could be a value (e.g. 1000, with a default sizelimit of 500) that won't affect the majority of normal search requests.
changed notes changed state Open to Test moved from Incoming to Software Bugs
changed notes changed state Test to Release
changed notes changed state Release to Closed
fixed in master fixed in RE25 fixed in RE24 (2.4.44) Optimization added (2.4.46)
changed notes