WIP: Detect connection socket close

src/backend/distributed/connection/connection_management.c

@@ -1562,6 +1562,8 @@ CitusAddWaitEventSetToSet(WaitEventSet *set, uint32 events, pgsocket fd,
 	volatile int waitEventSetIndex = WAIT_EVENT_SET_INDEX_NOT_INITIALIZED;
 	MemoryContext savedContext = CurrentMemoryContext;
 
+	events |= WL_SOCKET_CLOSED;
+
 	PG_TRY();
 	{
 		waitEventSetIndex =

src/backend/distributed/executor/adaptive_executor.c

@@ -2783,6 +2783,11 @@ ProcessWaitEvents(DistributedExecution *execution, WaitEvent *events, int eventC
 			ereport(ERROR, (errmsg("postmaster was shut down, exiting")));
 		}
 
+		if (event->events & WL_SOCKET_CLOSED)
+		{
+			ereport(WARNING, (errmsg("Connection closed detected")));
+		}
+
 		if (event->events & WL_LATCH_SET)
 		{
 			ResetLatch(MyLatch);
@@ -2808,6 +2813,7 @@ ProcessWaitEvents(DistributedExecution *execution, WaitEvent *events, int eventC
 		WorkerSession *session = (WorkerSession *) event->user_data;
 		session->latestUnconsumedWaitEvents = event->events;
 
+
 		ConnectionStateMachine(session);
 	}
 }
@@ -4158,6 +4164,8 @@ UpdateConnectionWaitFlags(WorkerSession *session, int waitFlags)
 	MultiConnection *connection = session->connection;
 	DistributedExecution *execution = session->workerPool->distributedExecution;
 
+	waitFlags |= WL_SOCKET_CLOSED;
+
 	/* do not take any actions if the flags not changed */
 	if (connection->waitFlags == waitFlags)
 	{
@@ -4202,6 +4210,11 @@ CheckConnectionReady(WorkerSession *session)
 		waitFlags = waitFlags | WL_SOCKET_WRITEABLE;
 	}
 
+	if ((session->latestUnconsumedWaitEvents & WL_SOCKET_CLOSED) != 0)
+	{
+		elog(WARNING, "DETECT SOCKET CLOSED");
+	}
+
 	if ((session->latestUnconsumedWaitEvents & WL_SOCKET_READABLE) != 0)
 	{
 		if (PQconsumeInput(connection->pgConn) == 0)

src/include/pg_version_compat.h

@@ -62,6 +62,12 @@ RelationGetSmgr(Relation rel)
 }
 
 
+/*
+ * Postgres 15+ supports detecting the remote connection closed. For earlier version,
+ * we simply ignore that.
+ */
+#define WL_SOCKET_CLOSED 0
+
 #endif
 
 #if PG_VERSION_NUM >= PG_VERSION_14