Re: Postgres, fsync, and OSs (specifically linux)

On Thu, May 17, 2018 at 11:45 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Thu, May 17, 2018 at 12:44 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>> Hi,
>>
>> On 2018-05-10 09:50:03 +0800, Craig Ringer wrote:
>>> while ((src = (RewriteMappingFile *) hash_seq_search(&seq_status)) != NULL)
>>> {
>>> if (FileSync(src->vfd, WAIT_EVENT_LOGICAL_REWRITE_SYNC) != 0)
>>> - ereport(ERROR,
>>> + ereport(PANIC,
>>> (errcode_for_file_access(),
>>> errmsg("could not fsync file \"%s\": %m", src->path)));
>>
>> To me this (and the other callers) doesn't quite look right. First, I
>> think we should probably be a bit more restrictive about when PANIC
>> out. It seems like we should PANIC on ENOSPC and EIO, but possibly not
>> others. Secondly, I think we should centralize the error handling. It
>> seems likely that we'll acrue some platform specific workarounds, and I
>> don't want to copy that knowledge everywhere.
>
> Maybe something like:
>
> ereport(promote_eio_to_panic(ERROR), ...)

Well, searching for places where error is reported with level PANIC,
using word PANIC would miss these instances. People will have to
remember to search with promote_eio_to_panic. May be handle the errors
inside FileSync() itself or a wrapper around that.

--
Best Wishes,
Ashutosh Bapat
EnterpriseDB Corporation
The Postgres Database Company