Add idle_in_transaction_session_timeout.

Vik Fearing, reviewed by Stéphane Schildknecht and me, and revised
slightly by me.

Author: robertmhaas

doc/src/sgml/config.sgml

@@ -6063,6 +6063,26 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-idle-in-transaction-session-timeout" xreflabel="idle_in_transaction_session_timeout">
+      <term><varname>idle_in_transaction_session_timeout</varname> (<type>integer</type>)
+      <indexterm>
+       <primary><varname>idle_in_transaction_session_timeout</> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+       Terminate any session with an open transaction that has been idle for
+       longer than the specified duration in milliseconds. This allows any
+       locks held by that session to be released and the connection slot to be reused;
+       it also allows tuples visible only to this transaction to be vacuumed.  See
+       <xref linkend="routine-vacuuming"> for more details about this.
+       </para>
+       <para>
+       The default value of 0 disables this feature.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-vacuum-freeze-table-age" xreflabel="vacuum_freeze_table_age">
       <term><varname>vacuum_freeze_table_age</varname> (<type>integer</type>)
       <indexterm>

doc/src/sgml/mvcc.sgml

@@ -725,7 +725,9 @@ ERROR:  could not serialize access due to read/write dependencies among transact
      <listitem>
       <para>
        Don't leave connections dangling <quote>idle in transaction</quote>
-       longer than necessary.
+       longer than necessary.  The configuration parameter
+       <xref linkend="guc-idle-in-transaction-session-timeout"> may be used to
+       automatically disconnect lingering sessions.
       </para>
      </listitem>
      <listitem>

src/backend/storage/lmgr/proc.c

@@ -58,6 +58,7 @@
 int			DeadlockTimeout = 1000;
 int			StatementTimeout = 0;
 int			LockTimeout = 0;
+int			IdleInTransactionSessionTimeout = 0;
 bool		log_lock_waits = false;
 
 /* Pointer to this process's PGPROC and PGXACT structs, if any */

src/backend/tcop/postgres.c

@@ -2978,6 +2978,18 @@ ProcessInterrupts(void)
 		}
 	}
 
+	if (IdleInTransactionSessionTimeoutPending)
+	{
+		/* Has the timeout setting changed since last we looked? */
+		if (IdleInTransactionSessionTimeout > 0)
+			ereport(FATAL,
+					(errcode(ERRCODE_IDLE_IN_TRANSACTION_SESSION_TIMEOUT),
+					 errmsg("terminating connection due to idle-in-transaction timeout")));
+		else
+			IdleInTransactionSessionTimeoutPending = false;
+
+	}
+
 	if (ParallelMessagePending)
 		HandleParallelMessages();
 }
@@ -3553,6 +3565,7 @@ PostgresMain(int argc, char *argv[],
 	StringInfoData input_message;
 	sigjmp_buf	local_sigjmp_buf;
 	volatile bool send_ready_for_query = true;
+	bool		disable_idle_in_transaction_timeout = false;
 
 	/* Initialize startup process environment if necessary. */
 	if (!IsUnderPostmaster)
@@ -3942,11 +3955,27 @@ PostgresMain(int argc, char *argv[],
 			{
 				set_ps_display("idle in transaction (aborted)", false);
 				pgstat_report_activity(STATE_IDLEINTRANSACTION_ABORTED, NULL);
+
+				/* Start the idle-in-transaction timer */
+				if (IdleInTransactionSessionTimeout > 0)
+				{
+					disable_idle_in_transaction_timeout = true;
+					enable_timeout_after(IDLE_IN_TRANSACTION_SESSION_TIMEOUT,
+										 IdleInTransactionSessionTimeout);
+				}
 			}
 			else if (IsTransactionOrTransactionBlock())
 			{
 				set_ps_display("idle in transaction", false);
 				pgstat_report_activity(STATE_IDLEINTRANSACTION, NULL);
+
+				/* Start the idle-in-transaction timer */
+				if (IdleInTransactionSessionTimeout > 0)
+				{
+					disable_idle_in_transaction_timeout = true;
+					enable_timeout_after(IDLE_IN_TRANSACTION_SESSION_TIMEOUT,
+										 IdleInTransactionSessionTimeout);
+				}
 			}
 			else
 			{
@@ -3987,7 +4016,16 @@ PostgresMain(int argc, char *argv[],
 		DoingCommandRead = false;
 
 		/*
-		 * (5) check for any other interesting events that happened while we
+		 * (5) turn off the idle-in-transaction timeout
+		 */
+		if (disable_idle_in_transaction_timeout)
+		{
+			disable_timeout(IDLE_IN_TRANSACTION_SESSION_TIMEOUT, false);
+			disable_idle_in_transaction_timeout = false;
+		}
+
+		/*
+		 * (6) check for any other interesting events that happened while we
 		 * slept.
 		 */
 		if (got_SIGHUP)
@@ -3997,7 +4035,7 @@ PostgresMain(int argc, char *argv[],
 		}
 
 		/*
-		 * (6) process the command.  But ignore it if we're skipping till
+		 * (7) process the command.  But ignore it if we're skipping till
 		 * Sync.
 		 */
 		if (ignore_till_sync && firstchar != EOF)

src/backend/utils/errcodes.txt

@@ -229,6 +229,7 @@ Section: Class 25 - Invalid Transaction State
 25007    E    ERRCODE_SCHEMA_AND_DATA_STATEMENT_MIXING_NOT_SUPPORTED         schema_and_data_statement_mixing_not_supported
 25P01    E    ERRCODE_NO_ACTIVE_SQL_TRANSACTION                              no_active_sql_transaction
 25P02    E    ERRCODE_IN_FAILED_SQL_TRANSACTION                              in_failed_sql_transaction
+25P03    E    ERRCODE_IDLE_IN_TRANSACTION_SESSION_TIMEOUT                    idle_in_transaction_session_timeout
 
 Section: Class 26 - Invalid SQL Statement Name
 

src/backend/utils/init/globals.c

@@ -30,6 +30,7 @@ volatile bool InterruptPending = false;
 volatile bool QueryCancelPending = false;
 volatile bool ProcDiePending = false;
 volatile bool ClientConnectionLost = false;
+volatile bool IdleInTransactionSessionTimeoutPending = false;
 volatile uint32 InterruptHoldoffCount = 0;
 volatile uint32 QueryCancelHoldoffCount = 0;
 volatile uint32 CritSectionCount = 0;

src/backend/utils/init/postinit.c

@@ -70,6 +70,7 @@ static void InitCommunication(void);
 static void ShutdownPostgres(int code, Datum arg);
 static void StatementTimeoutHandler(void);
 static void LockTimeoutHandler(void);
+static void IdleInTransactionSessionTimeoutHandler(void);
 static bool ThereIsAtLeastOneRole(void);
 static void process_startup_options(Port *port, bool am_superuser);
 static void process_settings(Oid databaseid, Oid roleid);
@@ -597,6 +598,8 @@ InitPostgres(const char *in_dbname, Oid dboid, const char *username,
 		RegisterTimeout(DEADLOCK_TIMEOUT, CheckDeadLockAlert);
 		RegisterTimeout(STATEMENT_TIMEOUT, StatementTimeoutHandler);
 		RegisterTimeout(LOCK_TIMEOUT, LockTimeoutHandler);
+		RegisterTimeout(IDLE_IN_TRANSACTION_SESSION_TIMEOUT,
+						IdleInTransactionSessionTimeoutHandler);
 	}
 
 	/*
@@ -1178,6 +1181,13 @@ LockTimeoutHandler(void)
 	kill(MyProcPid, SIGINT);
 }
 
+static void
+IdleInTransactionSessionTimeoutHandler(void)
+{
+	IdleInTransactionSessionTimeoutPending = true;
+	InterruptPending = true;
+	SetLatch(MyLatch);
+}
 
 /*
  * Returns true if at least one role is defined in this database cluster.

src/backend/utils/misc/guc.c

@@ -2065,6 +2065,17 @@ static struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"idle_in_transaction_session_timeout", PGC_USERSET, CLIENT_CONN_STATEMENT,
+			gettext_noop("Sets the maximum allowed duration of any idling transaction."),
+			gettext_noop("A value of 0 turns off the timeout."),
+			GUC_UNIT_MS
+		},
+		&IdleInTransactionSessionTimeout,
+		0, 0, INT_MAX,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"vacuum_freeze_min_age", PGC_USERSET, CLIENT_CONN_STATEMENT,
 			gettext_noop("Minimum age at which VACUUM should freeze a table row."),

src/backend/utils/misc/postgresql.conf.sample

@@ -529,6 +529,7 @@
 #session_replication_role = 'origin'
 #statement_timeout = 0			# in milliseconds, 0 is disabled
 #lock_timeout = 0			# in milliseconds, 0 is disabled
+#idle_in_transaction_session_timeout = 0		# in milliseconds, 0 is disabled
 #vacuum_freeze_min_age = 50000000
 #vacuum_freeze_table_age = 150000000
 #vacuum_multixact_freeze_min_age = 5000000

src/include/miscadmin.h

@@ -80,6 +80,7 @@
 extern PGDLLIMPORT volatile bool InterruptPending;
 extern PGDLLIMPORT volatile bool QueryCancelPending;
 extern PGDLLIMPORT volatile bool ProcDiePending;
+extern PGDLLIMPORT volatile bool IdleInTransactionSessionTimeoutPending;
 
 extern volatile bool ClientConnectionLost;