Fix handling of WAL segments ready to be archived during crash recovery

78ea8b5 has fixed an issue related to the recycling of WAL segments on
standbys depending on archive_mode.  However, it has introduced a
regression with the handling of WAL segments ready to be archived during
crash recovery, causing those files to be recycled without getting
archived.

This commit fixes the regression by tracking in shared memory if a live
cluster is either in crash recovery or archive recovery as the handling
of WAL segments ready to be archived is different in both cases (those
WAL segments should not be removed during crash recovery), and by using
this new shared memory state to decide if a segment can be recycled or
not.  Previously, it was not possible to know if a cluster was in crash
recovery or archive recovery as the shared state was able to track only
if recovery was happening or not, leading to the problem.

A set of TAP tests is added to close the gap here, making sure that WAL
segments ready to be archived are correctly handled when a cluster is in
archive or crash recovery with archive_mode set to "on" or "always", for
both standby and primary.

Reported-by: Benoît Lobréau
Author: Jehan-Guillaume de Rorthais
Reviewed-by: Kyotaro Horiguchi, Fujii Masao, Michael Paquier
Discussion: https://postgr.es/m/20200331172229.40ee00dc@firost
Backpatch-through: 9.5

1 files changed, 14 insertions, 7 deletions

diff --git a/src/backend/access/transam/xlogarchive.c b/src/backend/access/transam/xlogarchive.c
index d62c12310a1..55becd65d4d 100644
--- a/src/backend/access/transam/xlogarchive.c
+++ b/src/backend/access/transam/xlogarchive.c
@@ -572,18 +572,25 @@ XLogArchiveCheckDone(const char *xlog)
 {
 	char		archiveStatusPath[MAXPGPATH];
 	struct stat stat_buf;
-	bool		inRecovery = RecoveryInProgress();
+
+	/* The file is always deletable if archive_mode is "off". */
+	if (!XLogArchivingActive())
+		return true;
 
 	/*
-	 * The file is always deletable if archive_mode is "off".  On standbys
-	 * archiving is disabled if archive_mode is "on", and enabled with
-	 * "always".  On a primary, archiving is enabled if archive_mode is "on"
-	 * or "always".
+	 * During archive recovery, the file is deletable if archive_mode is not
+	 * "always".
 	 */
-	if (!((XLogArchivingActive() && !inRecovery) ||
-		  (XLogArchivingAlways() && inRecovery)))
+	if (!XLogArchivingAlways() &&
+		GetRecoveryState() == RECOVERY_STATE_ARCHIVE)
 		return true;
 
+	/*
+	 * At this point of the logic, note that we are either a primary with
+	 * archive_mode set to "on" or "always", or a standby with archive_mode
+	 * set to "always".
+	 */
+
 	/* First check for .done --- this means archiver is done with it */
 	StatusFilePath(archiveStatusPath, xlog, ".done");
 	if (stat(archiveStatusPath, &stat_buf) == 0)