From d42462a77bfb47a114b1e92f974ed557d25913cc Mon Sep 17 00:00:00 2001 From: Michael Paquier Date: Sat, 2 Sep 2017 21:15:04 +0900 Subject: [PATCH 2/2] Minimize window between history file and end-of-recovery record Once a standby node is promoted, this makes the assignment of the new timeline number booked earlier as the history file gets archived immediately. This way the other nodes are aware that this new timeline number is taken and should not be assigned to other nodes. The window between which the history file is archived and the end-of-recovery record is written cannot be zeroed, but this way it is minimized as much as possible. The new order of actions prevents as well a corrupted data directory on failure. --- src/backend/access/transam/xlog.c | 27 ++++++++++++++++++--------- 1 file changed, 18 insertions(+), 9 deletions(-) diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c index 64a7d24e85..b767c6a968 100644 --- a/src/backend/access/transam/xlog.c +++ b/src/backend/access/transam/xlog.c @@ -7524,6 +7524,24 @@ StartupXLOG(void) else snprintf(reason, sizeof(reason), "no recovery target specified"); + /* + * We are now done reading the old WAL. Turn off archive fetching + * if it was active, and make a writable copy of the last WAL segment. + * (Note that we also have a copy of the last block of the old WAL + * in readBuf; we will use that below.) + */ + exitArchiveRecovery(EndOfLogTLI, EndOfLog); + + /* + * Write the timeline history file, and have it archived. After this + * point (or rather, as soon as the file is archived), the timeline + * will appear as "taken" in the WAL archive and to any standby servers. + * If we crash before actually switching to the new timeline, standby + * servers will nevertheless think that we switched to the new timeline, + * and will try to connect to the new timeline. To minimize the window + * for that, try to do as little as possible between here and writing the + * end-of-recovery record. + */ writeTimeLineHistory(ThisTimeLineID, recoveryTargetTLI, EndRecPtr, reason); } @@ -7532,15 +7550,6 @@ StartupXLOG(void) XLogCtl->ThisTimeLineID = ThisTimeLineID; XLogCtl->PrevTimeLineID = PrevTimeLineID; - /* - * We are now done reading the old WAL. Turn off archive fetching if it - * was active, and make a writable copy of the last WAL segment. (Note - * that we also have a copy of the last block of the old WAL in readBuf; - * we will use that below.) - */ - if (ArchiveRecoveryRequested) - exitArchiveRecovery(EndOfLogTLI, EndOfLog); - /* * Prepare to write WAL starting at EndOfLog location, and init xlog * buffer cache using the block containing the last record from the -- 2.14.2