From 61913e7277e7c1c8f7a6573c2e3676a3fb0e70c2 Mon Sep 17 00:00:00 2001
From: Simon Rettberg
Date: Sun, 18 Aug 2019 20:54:17 +0200
Subject: [SERVER] altservers: Don't run check if <= 1 alt server available

---
 src/server/altservers.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

(limited to 'src/server/altservers.c')

diff --git a/src/server/altservers.c b/src/server/altservers.c
index 3d5e71e..60c046c 100644
--- a/src/server/altservers.c
+++ b/src/server/altservers.c
@@ -18,7 +18,7 @@ static dnbd3_connection_t * _Atomic pending[SERVER_MAX_PENDING_ALT_CHECKS];
 static dnbd3_signal_t * _Atomic runSignal = NULL;
 
 static dnbd3_alt_server_t altServers[SERVER_MAX_ALTS];
-static int numAltServers = 0;
+static atomic_int numAltServers = 0;
 static pthread_mutex_t altServersLock;
 
 static pthread_t altThread;
@@ -125,6 +125,8 @@ void altservers_findUplink(dnbd3_connection_t *uplink)
 {
 	if ( uplink->shutdown )
 		return;
+	if ( uplink->fd != -1 && numAltServers <= 1 )
+		return;
 	int i;
 	// if betterFd != -1 it means the uplink is supposed to switch to another
 	// server. As this function here is called by the uplink thread, it can
@@ -454,6 +456,13 @@ static void *altservers_main(void *data UNUSED)
 			dnbd3_connection_t * const uplink = pending[itLink];
 			if ( uplink == NULL )
 				continue;
+			// First, get 4 alt servers
+			numAlts = altservers_getListForUplink( servers, ALTS, uplink->fd == -1 );
+			// If we're already connected and only got one server anyways, there isn't much to do
+			if ( numAlts <= 1 && uplink->fd != -1 ) {
+				uplink->rttTestResult = RTT_DONTCHANGE;
+				continue;
+			}
 			dnbd3_image_t * const image = image_lock( uplink->image );
 			if ( image == NULL ) { // Check again after locking
 				mutex_lock( &uplink->rttLock );
@@ -461,13 +470,11 @@ static void *altservers_main(void *data UNUSED)
 				assert( pending[itLink] == uplink );
 				pending[itLink] = NULL;
 				mutex_unlock( &uplink->rttLock );
-				logadd( LOG_DEBUG1, "Image has gone away that was queued for RTT measurement" );
+				logadd( LOG_WARNING, "Image has gone away that was queued for RTT measurement" );
 				continue;
 			}
 			LOG( LOG_DEBUG2, "[%d] Running alt check", itLink );
 			assert( uplink->rttTestResult == RTT_INPROGRESS );
-			// Now get 4 alt servers
-			numAlts = altservers_getListForUplink( servers, ALTS, uplink->fd == -1 );
 			if ( uplink->fd != -1 ) {
 				// Add current server if not already in list
 				found = false;
-- 
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