Reword messages about impending (M)XID exhaustion.

First, we shouldn't recommend switching to single-user mode, because
that's terrible advice. Especially on newer versions where VACUUM
will enter emergency mode when nearing (M)XID exhaustion, it's
perfectly fine to just VACUUM in multi-user mode. Doing it that way
is less disruptive and avoids disabling the safeguards that prevent
actual wraparound, so recommend that instead.

Second, be more precise about what is going to happen (when we're
nearing the limits) or what is happening (when we actually hit them).
The database doesn't shut down, nor does it refuse all commands. It
refuses commands that assign whichever of XIDs and MXIDs are nearly
exhausted.

No back-patch. The existing hint that advises going to single-user
mode is sufficiently awful advice that removing it or changing it
might be justifiable even though we normally avoid changing
user-facing messages in back-branches, but I (rhaas) felt that it
was better to be more conservative and limit this fix to master
only. Aside from the usual risk of breaking translations, people
might be used to the existing message, or even have monitoring
scripts that look for it.

Alexander Alekseev, John Naylor, Robert Haas, reviewed at various
times by Peter Geoghegan, Hannu Krosing, and Andres Freund.

Discussion: http://postgr.es/m/CA+TgmoZBg95FiR9wVQPAXpGPRkacSt2okVge+PKPPFppN7sfnQ@mail.gmail.com

2 files changed, 10 insertions, 10 deletions

diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index 546d411610a..57ed34c0a88 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -2335,7 +2335,7 @@ SetMultiXactIdLimit(MultiXactId oldest_datminmxid, Oid oldest_datoid,
 								   multiWrapLimit - curMulti,
 								   oldest_datname,
 								   multiWrapLimit - curMulti),
-					 errhint("To avoid a database shutdown, execute a database-wide VACUUM in that database.\n"
+					 errhint("To avoid MultiXactId assignment failures, execute a database-wide VACUUM in that database.\n"
 							 "You might also need to commit or roll back old prepared transactions, or drop stale replication slots.")));
 		else
 			ereport(WARNING,
@@ -2344,7 +2344,7 @@ SetMultiXactIdLimit(MultiXactId oldest_datminmxid, Oid oldest_datoid,
 								   multiWrapLimit - curMulti,
 								   oldest_datoid,
 								   multiWrapLimit - curMulti),
-					 errhint("To avoid a database shutdown, execute a database-wide VACUUM in that database.\n"
+					 errhint("To avoid MultiXactId assignment failures, execute a database-wide VACUUM in that database.\n"
 							 "You might also need to commit or roll back old prepared transactions, or drop stale replication slots.")));
 	}
 }
diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 334adac09e8..abfee483174 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -126,16 +126,16 @@ GetNewTransactionId(bool isSubXact)
 			if (oldest_datname)
 				ereport(ERROR,
 						(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-						 errmsg("database is not accepting commands to avoid wraparound data loss in database \"%s\"",
+						 errmsg("database is not accepting commands that assign new XIDs to avoid wraparound data loss in database \"%s\"",
 								oldest_datname),
-						 errhint("Stop the postmaster and vacuum that database in single-user mode.\n"
+						 errhint("Execute a database-wide VACUUM in that database.\n"
 								 "You might also need to commit or roll back old prepared transactions, or drop stale replication slots.")));
 			else
 				ereport(ERROR,
 						(errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
-						 errmsg("database is not accepting commands to avoid wraparound data loss in database with OID %u",
+						 errmsg("database is not accepting commands that assign new XIDs to avoid wraparound data loss in database with OID %u",
 								oldest_datoid),
-						 errhint("Stop the postmaster and vacuum that database in single-user mode.\n"
+						 errhint("Execute a database-wide VACUUM in that database.\n"
 								 "You might also need to commit or roll back old prepared transactions, or drop stale replication slots.")));
 		}
 		else if (TransactionIdFollowsOrEquals(xid, xidWarnLimit))
@@ -148,14 +148,14 @@ GetNewTransactionId(bool isSubXact)
 						(errmsg("database \"%s\" must be vacuumed within %u transactions",
 								oldest_datname,
 								xidWrapLimit - xid),
-						 errhint("To avoid a database shutdown, execute a database-wide VACUUM in that database.\n"
+						 errhint("To avoid XID assignment failures, execute a database-wide VACUUM in that database.\n"
 								 "You might also need to commit or roll back old prepared transactions, or drop stale replication slots.")));
 			else
 				ereport(WARNING,
 						(errmsg("database with OID %u must be vacuumed within %u transactions",
 								oldest_datoid,
 								xidWrapLimit - xid),
-						 errhint("To avoid a database shutdown, execute a database-wide VACUUM in that database.\n"
+						 errhint("To avoid XID assignment failures, execute a database-wide VACUUM in that database.\n"
 								 "You might also need to commit or roll back old prepared transactions, or drop stale replication slots.")));
 		}
 
@@ -463,14 +463,14 @@ SetTransactionIdLimit(TransactionId oldest_datfrozenxid, Oid oldest_datoid)
 					(errmsg("database \"%s\" must be vacuumed within %u transactions",
 							oldest_datname,
 							xidWrapLimit - curXid),
-					 errhint("To avoid a database shutdown, execute a database-wide VACUUM in that database.\n"
+					 errhint("To avoid XID assignment failures, execute a database-wide VACUUM in that database.\n"
 							 "You might also need to commit or roll back old prepared transactions, or drop stale replication slots.")));
 		else
 			ereport(WARNING,
 					(errmsg("database with OID %u must be vacuumed within %u transactions",
 							oldest_datoid,
 							xidWrapLimit - curXid),
-					 errhint("To avoid a database shutdown, execute a database-wide VACUUM in that database.\n"
+					 errhint("To avoid XID assignment failures, execute a database-wide VACUUM in that database.\n"
 							 "You might also need to commit or roll back old prepared transactions, or drop stale replication slots.")));
 	}
 }