Use standard die() signal handler in walreceiver

This gets rid of the bespoken ProcessWalRcvInterrupts() function,
which lets walreceiver terminate at any CHECK_FOR_INTERRUPTS() call.
And it's less code anyway.

We can now use the standard libpqsrv_connect_params() libpq wrapper
from libpq-be-fe-helpers.h, removing more code. We attempted to do
that earlier already in commit 728f86f, but that was reverted
because it didn't call ProcessWalRcvInterrupts() and therefore didn't
react to shutdown requests. Now that ProcessWalRcvInterrupts() is
gone, it works. As stated in that commit, this also leads to
libpqwalreceiver reserving file descriptors for libpq conncetions,
which is nice.

Author: Andres Freund <[email protected]> (the earlier commit)
Author: Kyotaro Horiguchi <[email protected]>
Reviewed-by: Fujii Masao <[email protected]>
Reviewed-by: Yura Sokolov <[email protected]>

Author: hlinnaka

src/backend/replication/libpqwalreceiver/libpqwalreceiver.c

@@ -25,6 +25,7 @@
 #include "common/connect.h"
 #include "funcapi.h"
 #include "libpq-fe.h"
+#include "libpq/libpq-be-fe-helpers.h"
 #include "mb/pg_wchar.h"
 #include "miscadmin.h"
 #include "pgstat.h"
@@ -113,8 +114,6 @@ static WalReceiverFunctionsType PQWalReceiverFunctions = {
 };
 
 /* Prototypes for private functions */
-static PGresult *libpqrcv_PQexec(PGconn *streamConn, const char *query);
-static PGresult *libpqrcv_PQgetResult(PGconn *streamConn);
 static char *stringlist_to_identifierstr(PGconn *conn, List *strings);
 
 /*
@@ -148,7 +147,6 @@ libpqrcv_connect(const char *conninfo, bool replication, bool logical,
 				 bool must_use_password, const char *appname, char **err)
 {
 	WalReceiverConn *conn;
-	PostgresPollingStatusType status;
 	const char *keys[6];
 	const char *vals[6];
 	int			i = 0;
@@ -214,56 +212,17 @@ libpqrcv_connect(const char *conninfo, bool replication, bool logical,
 	Assert(i < lengthof(keys));
 
 	conn = palloc0(sizeof(WalReceiverConn));
-	conn->streamConn = PQconnectStartParams(keys, vals,
-											 /* expand_dbname = */ true);
-	if (PQstatus(conn->streamConn) == CONNECTION_BAD)
-		goto bad_connection_errmsg;
-
-	/*
-	 * Poll connection until we have OK or FAILED status.
-	 *
-	 * Per spec for PQconnectPoll, first wait till socket is write-ready.
-	 */
-	status = PGRES_POLLING_WRITING;
-	do
-	{
-		int			io_flag;
-		int			rc;
-
-		if (status == PGRES_POLLING_READING)
-			io_flag = WL_SOCKET_READABLE;
-#ifdef WIN32
-		/* Windows needs a different test while waiting for connection-made */
-		else if (PQstatus(conn->streamConn) == CONNECTION_STARTED)
-			io_flag = WL_SOCKET_CONNECTED;
-#endif
-		else
-			io_flag = WL_SOCKET_WRITEABLE;
-
-		rc = WaitLatchOrSocket(MyLatch,
-							   WL_EXIT_ON_PM_DEATH | WL_LATCH_SET | io_flag,
-							   PQsocket(conn->streamConn),
-							   0,
-							   WAIT_EVENT_LIBPQWALRECEIVER_CONNECT);
-
-		/* Interrupted? */
-		if (rc & WL_LATCH_SET)
-		{
-			ResetLatch(MyLatch);
-			ProcessWalRcvInterrupts();
-		}
-
-		/* If socket is ready, advance the libpq state machine */
-		if (rc & io_flag)
-			status = PQconnectPoll(conn->streamConn);
-	} while (status != PGRES_POLLING_OK && status != PGRES_POLLING_FAILED);
+	conn->streamConn =
+		libpqsrv_connect_params(keys, vals,
+								 /* expand_dbname = */ true,
+								WAIT_EVENT_LIBPQWALRECEIVER_CONNECT);
 
 	if (PQstatus(conn->streamConn) != CONNECTION_OK)
 		goto bad_connection_errmsg;
 
 	if (must_use_password && !PQconnectionUsedPassword(conn->streamConn))
 	{
-		PQfinish(conn->streamConn);
+		libpqsrv_disconnect(conn->streamConn);
 		pfree(conn);
 
 		ereport(ERROR,
@@ -281,8 +240,9 @@ libpqrcv_connect(const char *conninfo, bool replication, bool logical,
 	{
 		PGresult   *res;
 
-		res = libpqrcv_PQexec(conn->streamConn,
-							  ALWAYS_SECURE_SEARCH_PATH_SQL);
+		res = libpqsrv_exec(conn->streamConn,
+							ALWAYS_SECURE_SEARCH_PATH_SQL,
+							WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 		if (PQresultStatus(res) != PGRES_TUPLES_OK)
 		{
 			PQclear(res);
@@ -303,7 +263,7 @@ libpqrcv_connect(const char *conninfo, bool replication, bool logical,
 
 	/* error path, error already set */
 bad_connection:
-	PQfinish(conn->streamConn);
+	libpqsrv_disconnect(conn->streamConn);
 	pfree(conn);
 	return NULL;
 }
@@ -454,7 +414,9 @@ libpqrcv_identify_system(WalReceiverConn *conn, TimeLineID *primary_tli)
 	 * Get the system identifier and timeline ID as a DataRow message from the
 	 * primary server.
 	 */
-	res = libpqrcv_PQexec(conn->streamConn, "IDENTIFY_SYSTEM");
+	res = libpqsrv_exec(conn->streamConn,
+						"IDENTIFY_SYSTEM",
+						WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
 	{
 		PQclear(res);
@@ -631,7 +593,9 @@ libpqrcv_startstreaming(WalReceiverConn *conn,
 						 options->proto.physical.startpointTLI);
 
 	/* Start streaming. */
-	res = libpqrcv_PQexec(conn->streamConn, cmd.data);
+	res = libpqsrv_exec(conn->streamConn,
+						cmd.data,
+						WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 	pfree(cmd.data);
 
 	if (PQresultStatus(res) == PGRES_COMMAND_OK)
@@ -661,7 +625,7 @@ libpqrcv_endstreaming(WalReceiverConn *conn, TimeLineID *next_tli)
 	PGresult   *res;
 
 	/*
-	 * Send copy-end message.  As in libpqrcv_PQexec, this could theoretically
+	 * Send copy-end message.  As in libpqsrv_exec, this could theoretically
 	 * block, but the risk seems small.
 	 */
 	if (PQputCopyEnd(conn->streamConn, NULL) <= 0 ||
@@ -681,7 +645,8 @@ libpqrcv_endstreaming(WalReceiverConn *conn, TimeLineID *next_tli)
 	 * If we had not yet received CopyDone from the backend, PGRES_COPY_OUT is
 	 * also possible in case we aborted the copy in mid-stream.
 	 */
-	res = libpqrcv_PQgetResult(conn->streamConn);
+	res = libpqsrv_get_result(conn->streamConn,
+							  WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 	if (PQresultStatus(res) == PGRES_TUPLES_OK)
 	{
 		/*
@@ -696,7 +661,8 @@ libpqrcv_endstreaming(WalReceiverConn *conn, TimeLineID *next_tli)
 		PQclear(res);
 
 		/* the result set should be followed by CommandComplete */
-		res = libpqrcv_PQgetResult(conn->streamConn);
+		res = libpqsrv_get_result(conn->streamConn,
+								  WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 	}
 	else if (PQresultStatus(res) == PGRES_COPY_OUT)
 	{
@@ -710,7 +676,8 @@ libpqrcv_endstreaming(WalReceiverConn *conn, TimeLineID *next_tli)
 							pchomp(PQerrorMessage(conn->streamConn)))));
 
 		/* CommandComplete should follow */
-		res = libpqrcv_PQgetResult(conn->streamConn);
+		res = libpqsrv_get_result(conn->streamConn,
+								  WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 	}
 
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
@@ -721,7 +688,8 @@ libpqrcv_endstreaming(WalReceiverConn *conn, TimeLineID *next_tli)
 	PQclear(res);
 
 	/* Verify that there are no more results */
-	res = libpqrcv_PQgetResult(conn->streamConn);
+	res = libpqsrv_get_result(conn->streamConn,
+							  WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 	if (res != NULL)
 		ereport(ERROR,
 				(errcode(ERRCODE_PROTOCOL_VIOLATION),
@@ -746,7 +714,9 @@ libpqrcv_readtimelinehistoryfile(WalReceiverConn *conn,
 	 * Request the primary to send over the history file for given timeline.
 	 */
 	snprintf(cmd, sizeof(cmd), "TIMELINE_HISTORY %u", tli);
-	res = libpqrcv_PQexec(conn->streamConn, cmd);
+	res = libpqsrv_exec(conn->streamConn,
+						cmd,
+						WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
 	{
 		PQclear(res);
@@ -776,114 +746,13 @@ libpqrcv_readtimelinehistoryfile(WalReceiverConn *conn,
 	PQclear(res);
 }
 
-/*
- * Send a query and wait for the results by using the asynchronous libpq
- * functions and socket readiness events.
- *
- * The function is modeled on libpqsrv_exec(), with the behavior difference
- * being that it calls ProcessWalRcvInterrupts().  As an optimization, it
- * skips try/catch, since all errors terminate the process.
- *
- * May return NULL, rather than an error result, on failure.
- */
-static PGresult *
-libpqrcv_PQexec(PGconn *streamConn, const char *query)
-{
-	PGresult   *lastResult = NULL;
-
-	/*
-	 * PQexec() silently discards any prior query results on the connection.
-	 * This is not required for this function as it's expected that the caller
-	 * (which is this library in all cases) will behave correctly and we don't
-	 * have to be backwards compatible with old libpq.
-	 */
-
-	/*
-	 * Submit the query.  Since we don't use non-blocking mode, this could
-	 * theoretically block.  In practice, since we don't send very long query
-	 * strings, the risk seems negligible.
-	 */
-	if (!PQsendQuery(streamConn, query))
-		return NULL;
-
-	for (;;)
-	{
-		/* Wait for, and collect, the next PGresult. */
-		PGresult   *result;
-
-		result = libpqrcv_PQgetResult(streamConn);
-		if (result == NULL)
-			break;				/* query is complete, or failure */
-
-		/*
-		 * Emulate PQexec()'s behavior of returning the last result when there
-		 * are many.  We are fine with returning just last error message.
-		 */
-		PQclear(lastResult);
-		lastResult = result;
-
-		if (PQresultStatus(lastResult) == PGRES_COPY_IN ||
-			PQresultStatus(lastResult) == PGRES_COPY_OUT ||
-			PQresultStatus(lastResult) == PGRES_COPY_BOTH ||
-			PQstatus(streamConn) == CONNECTION_BAD)
-			break;
-	}
-
-	return lastResult;
-}
-
-/*
- * Perform the equivalent of PQgetResult(), but watch for interrupts.
- */
-static PGresult *
-libpqrcv_PQgetResult(PGconn *streamConn)
-{
-	/*
-	 * Collect data until PQgetResult is ready to get the result without
-	 * blocking.
-	 */
-	while (PQisBusy(streamConn))
-	{
-		int			rc;
-
-		/*
-		 * We don't need to break down the sleep into smaller increments,
-		 * since we'll get interrupted by signals and can handle any
-		 * interrupts here.
-		 */
-		rc = WaitLatchOrSocket(MyLatch,
-							   WL_EXIT_ON_PM_DEATH | WL_SOCKET_READABLE |
-							   WL_LATCH_SET,
-							   PQsocket(streamConn),
-							   0,
-							   WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
-
-		/* Interrupted? */
-		if (rc & WL_LATCH_SET)
-		{
-			ResetLatch(MyLatch);
-			ProcessWalRcvInterrupts();
-		}
-
-		/* Consume whatever data is available from the socket */
-		if (PQconsumeInput(streamConn) == 0)
-		{
-			/* trouble; return NULL */
-			return NULL;
-		}
-	}
-
-	/* Now we can collect and return the next PGresult */
-	return PQgetResult(streamConn);
-}
-
 /*
  * Disconnect connection to primary, if any.
  */
 static void
 libpqrcv_disconnect(WalReceiverConn *conn)
 {
-	PQfinish(conn->streamConn);
+	libpqsrv_disconnect(conn->streamConn);
 	PQfreemem(conn->recvBuf);
 	pfree(conn);
 }
@@ -937,13 +806,15 @@ libpqrcv_receive(WalReceiverConn *conn, char **buffer,
 	{
 		PGresult   *res;
 
-		res = libpqrcv_PQgetResult(conn->streamConn);
+		res = libpqsrv_get_result(conn->streamConn,
+								  WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 		if (PQresultStatus(res) == PGRES_COMMAND_OK)
 		{
 			PQclear(res);
 
 			/* Verify that there are no more results. */
-			res = libpqrcv_PQgetResult(conn->streamConn);
+			res = libpqsrv_get_result(conn->streamConn,
+									  WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 			if (res != NULL)
 			{
 				PQclear(res);
@@ -1094,7 +965,9 @@ libpqrcv_create_slot(WalReceiverConn *conn, const char *slotname,
 			appendStringInfoString(&cmd, " PHYSICAL RESERVE_WAL");
 	}
 
-	res = libpqrcv_PQexec(conn->streamConn, cmd.data);
+	res = libpqsrv_exec(conn->streamConn,
+						cmd.data,
+						WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 	pfree(cmd.data);
 
 	if (PQresultStatus(res) != PGRES_TUPLES_OK)
@@ -1147,7 +1020,8 @@ libpqrcv_alter_slot(WalReceiverConn *conn, const char *slotname,
 
 	appendStringInfoString(&cmd, " );");
 
-	res = libpqrcv_PQexec(conn->streamConn, cmd.data);
+	res = libpqsrv_exec(conn->streamConn, cmd.data,
+						WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 	pfree(cmd.data);
 
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
@@ -1214,7 +1088,7 @@ libpqrcv_processTuples(PGresult *pgres, WalRcvExecResult *walres,
 	{
 		char	   *cstrs[MaxTupleAttributeNumber];
 
-		ProcessWalRcvInterrupts();
+		CHECK_FOR_INTERRUPTS();
 
 		/* Do the allocations in temporary context. */
 		oldcontext = MemoryContextSwitchTo(rowcontext);
@@ -1260,7 +1134,9 @@ libpqrcv_exec(WalReceiverConn *conn, const char *query,
 				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
 				 errmsg("the query interface requires a database connection")));
 
-	pgres = libpqrcv_PQexec(conn->streamConn, query);
+	pgres = libpqsrv_exec(conn->streamConn,
+						  query,
+						  WAIT_EVENT_LIBPQWALRECEIVER_RECEIVE);
 
 	switch (PQresultStatus(pgres))
 	{