On Mon, 17 Jan 2022 at 15:25, Bharath Rupireddy <bharath.rupireddyforpostg...@gmail.com> wrote: > > On Mon, Jan 17, 2022 at 8:14 PM Thom Brown <t...@linux.com> wrote: > > > > Hi, > > > > Should archive_command being blank when archiving is enabled result in > > a fatal error? This doesn't even produce a warning when restarting, > > just an entry in the log when it goes to archive a WAL segment, and > > finds the archive_command is empty. > > > > Is there a valid scenario where someone would have archiving enabled > > but no archive command? Naturally it will build up WAL until it is > > corrected, which will result in a less desirable error, and likely at > > a less convenient time, and to avoid it, someone either has to have > > checked the logs and noticed this error, or got curious as to why > > their WAL collection is nearly running out of shelf space. > > Yes, the .ready files under archive_status and wal files under pg_wal > directory grow up with archive_mode on but no archive_command. The > archiver keeps emitting "archive_mode enabled, yet archive_command is > not set" warnings into server logs, maybe this is something that needs > to be monitored for. The expectation is to have a good archiving > configuration setup in place which updates both archive_command and > archive_mode to appropriate values. > > The server keeps the WAL files from the point when archive_mode is > enabled, but not from the point when the archive_command is set. The > archive_mode needs postmaster restart whereas archive_command doesn't, > if the archive_command too needed a postmaster restart, then we would > have failed FATALly if archive_command was empty. But making the > archive_command a needs-postmaster-restart class of parameter is not > the path we go IMO because avoiding pomaster restarts in production > environments is to be avoided whenever possible.
Okay, that makes sense. Thanks. I guess people have to be careful with their settings. I was hoping there was one less footgun that could be disarmed. > > An extreme scenario I can think of is if the archive_command is set to > empty by a service layer code. Of course, this is something postgres > doesn't need to care about. However, a reasonable thing to do is to > emit a WARNING or ERROR-out when archive_command is set to null in > it's check_archive_command when archive_mode is on? > > Regards, > Bharath Rupireddy. -- Thom
