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Abort transactions that sits idle for too long. (#20077)

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Set `idle_in_transaction_session_timeout` on new postgres connections

Idle transactions can block maintenance tasks server-side like vacuums,
which can lead to bloat and performance issues.

We should never hit this timeout in normal operation, as Synapse should
always be actively using the connection when in a transaction and so it
should only ever be briefly idle. If we do hit this timeout, it's likely
that no progress is being made and so aborting the session is safe.

In certain cases we have seen connections leak, particularly when using
a connection pooler like pgcat, and this timeout will help with that.

---------

Co-authored-by: Eric Eastwood <erice@element.io>
This commit is contained in:
Erik Johnston
2026-08-10 15:46:39 +01:00
committed by GitHub
co-authored by Eric Eastwood
parent 8aef536bbe
commit 81a42c42ad
2 changed files with 27 additions and 0 deletions
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changelog.d/20077.misc
+1
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@@ -0,0 +1 @@
Set `idle_in_transaction_session_timeout` (default 30 minutes) on new PostgreSQL connections, so that wedged connections don't hold locks or block vacuum indefinitely.
synapse/storage/engines/postgres.py
+26
View File
@@ -65,6 +65,24 @@ class PostgresEngine(
self.statement_timeout: int | None = database_config.get(
"statement_timeout", Duration(minutes=10).as_millis()
)
# Abort transactions that sit idle for too long.
#
# Idle transactions can block maintenance tasks server-side like
# vacuums, which can lead to bloat and performance issues.
#
# We should never hit this timeout in normal operation, as Synapse
# should always be actively using the connection when in a transaction
# and so it should only ever be briefly idle. If we do hit this timeout,
# it's likely that no progress is being made and so aborting the session
# is safe.
#
# In certain cases we have seen connections leak, particularly when
# using a connection pooler like pgcat, and this timeout will help with
# that.
self.idle_in_transaction_session_timeout: int | None = database_config.get(
"idle_in_transaction_session_timeout", Duration(minutes=30).as_millis()
)
self._version: int | None = None # unknown as yet
self.isolation_level_map: Mapping[int, int] = {
@@ -187,6 +205,14 @@ class PostgresEngine(
if self.statement_timeout is not None:
cursor.execute("SET statement_timeout TO ?", (self.statement_timeout,))
# Abort transactions that sit idle for too long, as they hold locks
# and block vacuum.
if self.idle_in_transaction_session_timeout is not None:
cursor.execute(
"SET idle_in_transaction_session_timeout TO ?",
(self.idle_in_transaction_session_timeout,),
)
cursor.close()
db_conn.commit()