Hey Hackers, If a postmaster is running and the pg_control file is removed postgres will PANIC.
Steps to recreate: 1.) start a new cluster 2.) rm $DATADIR/pg_control 3.) psql => CHECKPOINT; PANIC: could not open control file "global/pg_control": No such file or directory After the PANIC there is no pg_control. Recovery would be difficult without a replica or a backup. Instead of crashing we can just write a new pg_control file since all the data is in memory at the time. There does not really seem to be a need for this behavior as all the information postgres needs is in memory at this point. I propose with a patch to just recreate pg_control on updates if it does not exist. -- Brian Faherty
From 80b84792d3c54a90e1e221c818a7ef025fe30b61 Mon Sep 17 00:00:00 2001 From: Brian Faherty <anothergenericu...@gmail.com> Date: Mon, 23 Jul 2018 15:08:57 -0400 Subject: [PATCH] Create pg_control on update if not exists Removing the global/pg_control file on a running postgres cluster will no longer crash the postmaster during a checkpoint. --- src/backend/access/transam/xlog.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 335b4a573d..4721ea0168 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -4758,7 +4758,7 @@ UpdateControlFile(void) FIN_CRC32C(ControlFile->crc); fd = BasicOpenFile(XLOG_CONTROL_FILE, - O_RDWR | PG_BINARY); + O_RDWR | O_CREAT | PG_BINARY); if (fd < 0) ereport(PANIC, (errcode_for_file_access(), -- 2.17.1
