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Reduce overhead of renaming archive status files.

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Presently, archive status files are durably renamed from .ready to
.done to indicate that a file has been archived.  Persisting this
rename to disk accounts for a significant amount of the overhead
associated with archiving.  While durably renaming the file
prevents re-archiving in most cases, archive commands and libraries
must already gracefully handle attempts to re-archive the last
archived file after a crash (e.g., a crash immediately after
archive_command exits but before the server renames the status
file).

This change reduces the amount of overhead associated with
archiving by using rename() instead of durable_rename() to rename
the archive status files.  As a consequence, the server is more
likely to attempt to re-archive files after a crash, but as noted
above, archive commands and modules are already expected to handle
this.  It is also possible that the server will attempt to re-
archive files that have been removed or recycled, but the archiver
already handles this, too.

Author: Nathan Bossart
Reviewed-by: Kyotaro Horiguchi, Fujii Masao
Discussion: https://postgr.es/m/20220222011948.GA3850532@nathanxps13
This commit is contained in:
Fujii Masao 2022-07-26 16:00:18 +09:00
parent 27e0ee57f6
commit 756e221db6
1 changed files with 13 additions and 1 deletions
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14
src/backend/postmaster/pgarch.c
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@ -745,7 +745,19 @@ pgarch_archiveDone(char *xlog)
StatusFilePath(rlogready, xlog, ".ready");
StatusFilePath(rlogdone, xlog, ".done");
(void) durable_rename(rlogready, rlogdone, WARNING);
/*
* To avoid extra overhead, we don't durably rename the .ready file to
* .done. Archive commands and libraries must gracefully handle attempts
* to re-archive files (e.g., if the server crashes just before this
* function is called), so it should be okay if the .ready file reappears
* after a crash.
*/
if (rename(rlogready, rlogdone) < 0)
ereport(WARNING,
(errcode_for_file_access(),
errmsg("could not rename file \"%s\" to \"%s\": %m",
rlogready, rlogdone)));
}