walreceiver-latch-1.patch

diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index ddf7d79..40e1718 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -46,6 +46,7 @@
 #include "storage/bufmgr.h"
 #include "storage/fd.h"
 #include "storage/ipc.h"
+#include "storage/latch.h"
 #include "storage/pmsignal.h"
 #include "storage/procarray.h"
 #include "storage/smgr.h"
@@ -9139,6 +9140,13 @@ startupproc_quickdie(SIGNAL_ARGS)
 }
 
 
+/* SIGUSR1: let latch facility handle the signal */
+static void
+StartupProcSigUsr1Handler(SIGNAL_ARGS)
+{
+	latch_sigusr1_handler();
+}
+
 /* SIGHUP: set flag to re-read config file at next convenient time */
 static void
 StartupProcSigHupHandler(SIGNAL_ARGS)
@@ -9213,7 +9221,7 @@ StartupProcessMain(void)
 	else
 		pqsignal(SIGALRM, SIG_IGN);
 	pqsignal(SIGPIPE, SIG_IGN);
-	pqsignal(SIGUSR1, SIG_IGN);
+	pqsignal(SIGUSR1, StartupProcSigUsr1Handler);
 	pqsignal(SIGUSR2, SIG_IGN);
 
 	/*
@@ -9397,16 +9405,13 @@ retry:
 					}
 
 					/*
-					 * Data not here yet, so check for trigger then sleep.
+					 * Data not here yet, so check for trigger then sleep for
+					 * five seconds like in the WAL file polling case below.
 					 */
 					if (CheckForStandbyTrigger())
 						goto triggered;
 
-					/*
-					 * When streaming is active, we want to react quickly when
-					 * the next WAL record arrives, so sleep only a bit.
-					 */
-					pg_usleep(100000L); /* 100ms */
+					WaitForWalArrival(5000000L);
 				}
 				else
 				{
diff --git a/src/backend/replication/walreceiver.c b/src/backend/replication/walreceiver.c
index b868707..e12f1f5 100644
--- a/src/backend/replication/walreceiver.c
+++ b/src/backend/replication/walreceiver.c
@@ -529,6 +529,9 @@ XLogWalRcvFlush(void)
 		walrcv->receivedUpto = LogstreamResult.Flush;
 		SpinLockRelease(&walrcv->mutex);
 
+		/* Signal the startup process that new WAL has arrived */
+		SetLatch(&walrcv->receivedLatch);
+
 		/* Report XLOG streaming progress in PS display */
 		if (update_process_title)
 		{
diff --git a/src/backend/replication/walreceiverfuncs.c b/src/backend/replication/walreceiverfuncs.c
index b206885..8182160 100644
--- a/src/backend/replication/walreceiverfuncs.c
+++ b/src/backend/replication/walreceiverfuncs.c
@@ -64,6 +64,7 @@ WalRcvShmemInit(void)
 		MemSet(WalRcv, 0, WalRcvShmemSize());
 		WalRcv->walRcvState = WALRCV_STOPPED;
 		SpinLockInit(&WalRcv->mutex);
+		InitSharedLatch(&WalRcv->receivedLatch);
 	}
 }
 
@@ -163,6 +164,9 @@ ShutdownWalRcv(void)
 
 		pg_usleep(100000);		/* 100ms */
 	}
+
+	/* We don't need the latch anymore */
+	DisownLatch(&walrcv->receivedLatch);
 }
 
 /*
@@ -187,6 +191,9 @@ RequestXLogStreaming(XLogRecPtr recptr, const char *conninfo)
 	if (recptr.xrecoff % XLogSegSize != 0)
 		recptr.xrecoff -= recptr.xrecoff % XLogSegSize;
 
+	/*
+	 * Update shared memory status with information needed by walreceiver
+	 */
 	SpinLockAcquire(&walrcv->mutex);
 
 	/* It better be stopped before we try to restart it */
@@ -204,6 +211,10 @@ RequestXLogStreaming(XLogRecPtr recptr, const char *conninfo)
 
 	SpinLockRelease(&walrcv->mutex);
 
+	/* Take ownership of the latch so that we can wait on it */
+	OwnLatch(&walrcv->receivedLatch);
+
+	/* Request postmaster to start the walreceiver process */
 	SendPostmasterSignal(PMSIGNAL_START_WALRECEIVER);
 }
 
@@ -229,3 +240,20 @@ GetWalRcvWriteRecPtr(XLogRecPtr *latestChunkStart)
 
 	return recptr;
 }
+
+/*
+ * Wait for more WAL to arrive, or timeout (in microseconds) to be reached
+ */
+void
+WaitForWalArrival(int timeout)
+{
+	/* Wait for more WAL to arrive */
+	if (WaitLatch(&WalRcv->receivedLatch, timeout))
+	{
+		/*
+		 * Reset the latch so that next call to WaitForWalArrival will sleep
+		 * again.
+		 */
+		ResetLatch(&WalRcv->receivedLatch);
+	}
+}
diff --git a/src/include/replication/walreceiver.h b/src/include/replication/walreceiver.h
index 2ea881e..66a8229 100644
--- a/src/include/replication/walreceiver.h
+++ b/src/include/replication/walreceiver.h
@@ -13,6 +13,7 @@
 #define _WALRECEIVER_H
 
 #include "access/xlogdefs.h"
+#include "storage/latch.h"
 #include "storage/spin.h"
 #include "pgtime.h"
 
@@ -72,6 +73,13 @@ typedef struct
 	char		conninfo[MAXCONNINFO];
 
 	slock_t		mutex;			/* locks shared variables shown above */
+
+	/*
+	 * Walreceiver sets this latch every time new WAL has been received and
+	 * fsync'd to disk, allowing startup process to wait for new WAL to
+	 * arrive.
+	 */
+	Latch		receivedLatch;
 } WalRcvData;
 
 extern WalRcvData *WalRcv;
@@ -92,8 +100,8 @@ extern Size WalRcvShmemSize(void);
 extern void WalRcvShmemInit(void);
 extern void ShutdownWalRcv(void);
 extern bool WalRcvInProgress(void);
-extern XLogRecPtr WaitNextXLogAvailable(XLogRecPtr recptr, bool *finished);
 extern void RequestXLogStreaming(XLogRecPtr recptr, const char *conninfo);
 extern XLogRecPtr GetWalRcvWriteRecPtr(XLogRecPtr *latestChunkStart);
+extern void WaitForWalArrival(int timeout);
 
 #endif   /* _WALRECEIVER_H */