Re: .ready and .done files considered harmful
| От | Dipesh Pandit |
|---|---|
| Тема | Re: .ready and .done files considered harmful |
| Дата | |
| Msg-id | CAN1g5_ECegnUtHM-fg66UN=f1qFXJ_rZyrC+QoGcURJMOB-+Rw@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: .ready and .done files considered harmful ("Bossart, Nathan" <bossartn@amazon.com>) |
| Ответы |
Re: .ready and .done files considered harmful
|
| Список | pgsql-hackers |
Thanks for the feedback.
> + StatusFilePath(archiveStatusPath, xlog, ".ready");
> + if (stat(archiveStatusPath, &stat_buf) == 0)
> + PgArchEnableDirScan();
> We may want to call PgArchWakeup() after setting the flag.
Yes, added a call to wake up archiver.
> >
> > I wonder if we really need to perform a directory scan in this case.
> > Unless there are other cases where the .ready files are created out of
> > order, I think this just causes an unnecessary directory scan every
> > time the archiver catches up.
> Thinking further, I suppose this is necessary for when lastSegNo gets
> reset after processing an out-of-order .ready file.
Also, this is necessary when lastTLI gets reset after switching to a new
timeline.
> + pg_atomic_flag dirScan;
> I personally don't think it's necessary to use an atomic here. A
> spinlock or LWLock would probably work just fine, as contention seems
> unlikely. If we use a lock, we also don't have to worry about memory
> barriers.
> I personally don't think it's necessary to use an atomic here. A
> spinlock or LWLock would probably work just fine, as contention seems
> unlikely. If we use a lock, we also don't have to worry about memory
> barriers.
History file should be archived as soon as it gets created. The atomic flag
here will make sure that there is no reordering of read/write instructions while
accessing the flag in shared memory. Archiver needs to read this flag at the
here will make sure that there is no reordering of read/write instructions while
accessing the flag in shared memory. Archiver needs to read this flag at the
beginning of each cycle. Write to atomic flag is synchronized and it provides
a lockless read. I think an atomic flag here is an efficient choice unless I am
missing something.
Please find the attached patch v7.
Thanks,
Dipesh
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