Horton

Re: logical decoding : exceeded maxAllocatedDescs for .spill files

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Noah Misch <noah@leadboat.com>, Amit Khandekar <amitdkhan.pg@gmail.com>, Alvaro Herrera from 2ndQuadrant <alvherre@alvh.no-ip.org>, Andres Freund <andres@anarazel.de>, Juan José Santamaría Flecha <juanjo.santamaria@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Robert Haas <robertmhaas@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>
Date: 2020-01-11T05:36:35Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. When a TAP file has non-zero exit status, retain temporary directories.

  2. Fix running out of file descriptors for spill files.

  3. Track statistics for spilling of changes from ReorderBuffer.

  4. Handle ReadFile() EOF correctly on Windows.

  5. Add logical_decoding_work_mem to limit ReorderBuffer memory usage.

  6. Generational memory allocator

  7. Support retaining data dirs on successful TAP tests

Attachments

On Fri, Jan 10, 2020 at 9:31 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
>
> On Fri, Jan 10, 2020 at 6:10 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> >
> > I wrote:
> > >           ReorderBuffer: 223302560 total in 26995 blocks; 7056 free (3 chunks); 223295504 used
> >
> > > The test case is only inserting 50K fairly-short rows, so this seems
> > > like an unreasonable amount of memory to be consuming for that; and
> > > even if you think it's reasonable, it clearly isn't going to scale
> > > to large production transactions.
> >
> > > Now, the good news is that v11 and later get through
> > > 006_logical_decoding.pl just fine under the same restriction.
> > > So we did something in v11 to fix this excessive memory consumption.
> > > However, unless we're willing to back-port whatever that was, this
> > > test case is clearly consuming excessive resources for the v10 branch.
> >
> > I dug around a little in the git history for backend/replication/logical/,
> > and while I find several commit messages mentioning memory leaks and
> > faulty spill logic, they all claim to have been back-patched as far
> > as 9.4.
> >
> > It seems reasonably likely to me that this result is telling us about
> > an actual bug, ie, faulty back-patching of one or more of those fixes
> > into v10 and perhaps earlier branches.
> >
>
> I think it would be good to narrow down this problem, but it seems we
> can do this separately.   I think to avoid forgetting about this, can
> we track it somewhere as an open issue (In Older Bugs section of
> PostgreSQL 12 Open Items or some other place)?
>
> It seems to me that this test has found a problem in back-branches, so
> we might want to keep it after removing the max_files_per_process
> restriction.  However, unless we narrow down this memory leak it is
> not a good idea to keep it at least not in v10.  So, we have the below
> options:
> (a) remove this test entirely from all branches and once we found the
> memory leak problem in back-branches, then consider adding it again
> without max_files_per_process restriction.
> (b) keep this test without max_files_per_process restriction till v11
> and once the memory leak issue in v10 is found, we can back-patch to
> v10 as well.
>

I am planning to go with option (a) and attached are patches to revert
the entire test on HEAD and back branches.  I am planning to commit
these by Tuesday unless someone has a better idea.

-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com