diff options
| author | Noah Misch <noah@leadboat.com> | 2020-08-15 10:15:53 -0700 |
|---|---|---|
| committer | Noah Misch <noah@leadboat.com> | 2020-08-15 10:15:57 -0700 |
| commit | e525770dd504e5f182229b9bee64430ebe71a2a8 (patch) | |
| tree | e51aa6374e2eefc8b1fbab6e95ed5559b5f1c661 /doc/src | |
| parent | dea07098af20f3dbaac873263020a5d95ea24ed8 (diff) | |
Prevent concurrent SimpleLruTruncate() for any given SLRU.
The SimpleLruTruncate() header comment states the new coding rule. To
achieve this, add locktype "frozenid" and two LWLocks. This closes a
rare opportunity for data loss, which manifested as "apparent
wraparound" or "could not access status of transaction" errors. Data
loss is more likely in pg_multixact, due to released branches' thin
margin between multiStopLimit and multiWrapLimit. If a user's physical
replication primary logged ": apparent wraparound" messages, the user
should rebuild standbys of that primary regardless of symptoms. At less
risk is a cluster having emitted "not accepting commands" errors or
"must be vacuumed" warnings at some point. One can test a cluster for
this data loss by running VACUUM FREEZE in every database. Back-patch
to 9.5 (all supported versions).
Discussion: https://postgr.es/m/20190218073103.GA1434723@rfd.leadboat.com
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/catalogs.sgml | 4 | ||||
| -rw-r--r-- | doc/src/sgml/monitoring.sgml | 20 |
2 files changed, 21 insertions, 3 deletions
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml index f314f93051d..96e55193f19 100644 --- a/doc/src/sgml/catalogs.sgml +++ b/doc/src/sgml/catalogs.sgml @@ -8886,7 +8886,8 @@ SCRAM-SHA-256$<replaceable><iteration count></>:<replaceable><salt>< and general database objects (identified by class OID and object OID, in the same way as in <structname>pg_description</structname> or <structname>pg_depend</structname>). Also, the right to extend a - relation is represented as a separate lockable object. + relation is represented as a separate lockable object, as is the right to + update <structname>pg_database</structname>.<structfield>datfrozenxid</structfield>. Also, <quote>advisory</> locks can be taken on numbers that have user-defined meanings. </para> @@ -8912,6 +8913,7 @@ SCRAM-SHA-256$<replaceable><iteration count></>:<replaceable><salt>< Type of the lockable object: <literal>relation</>, <literal>extend</>, + <literal>frozenid</literal>, <literal>page</>, <literal>tuple</>, <literal>transactionid</>, diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml index c492114f331..601616ec2ce 100644 --- a/doc/src/sgml/monitoring.sgml +++ b/doc/src/sgml/monitoring.sgml @@ -845,7 +845,7 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser <tbody> <row> - <entry morerows="62"><literal>LWLock</></entry> + <entry morerows="64"><literal>LWLock</></entry> <entry><literal>ShmemIndexLock</></entry> <entry>Waiting to find or allocate space in shared memory.</entry> </row> @@ -1044,6 +1044,16 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser the oldest transaction id available to it.</entry> </row> <row> + <entry><literal>WrapLimitsVacuumLock</literal></entry> + <entry>Waiting to update limits on transaction id and multixact + consumption.</entry> + </row> + <row> + <entry><literal>NotifyQueueTailLock</literal></entry> + <entry>Waiting to update limit on notification message + storage.</entry> + </row> + <row> <entry><literal>clog</></entry> <entry>Waiting for I/O on a clog (transaction status) buffer.</entry> </row> @@ -1118,7 +1128,7 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser <entry>Waiting for TBM shared iterator lock.</entry> </row> <row> - <entry morerows="9"><literal>Lock</></entry> + <entry morerows="10"><literal>Lock</></entry> <entry><literal>relation</></entry> <entry>Waiting to acquire a lock on a relation.</entry> </row> @@ -1127,6 +1137,12 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser <entry>Waiting to extend a relation.</entry> </row> <row> + <entry><literal>frozenid</literal></entry> + <entry>Waiting to + update <structname>pg_database</structname>.<structfield>datfrozenxid</structfield> + and <structname>pg_database</structname>.<structfield>datminmxid</structfield>.</entry> + </row> + <row> <entry><literal>page</></entry> <entry>Waiting to acquire a lock on page of a relation.</entry> </row> |