From: Marko Kreen <markokr@gmail.com>
Date: Wed, 19 Nov 2008 12:06:37 +0000 (+0000)
Subject: New tunable 'sbuf_loopcnt' to limit time spent on one socket.
X-Git-Tag: pgbouncer_1_3_rc1~42
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=ac4ab0fc88a17fff8cad6f07da9ff12b1f025276;p=pgbouncer

New tunable 'sbuf_loopcnt' to limit time spent on one socket.

In some situations - eg SMP server, local Postgres and fast network -
pgbouncer can run recv()->send() loop many times without blocking
on either side.  But that means other connections will stall for
a long time.  To make processing more fair, limit the times
of doing recv()->send() one socket.  If count reaches limit,
just proceed processing other sockets.  The processing for
that socket will resume on next event loop.

Thanks to Alexander Schöcke for report and testing.
---

diff --git a/doc/config.txt b/doc/config.txt
index d5adbd5..7eba7e3 100644
--- a/doc/config.txt
+++ b/doc/config.txt
@@ -303,6 +303,15 @@ large.
 
 Default: 2048
 
+==== sbuf_loopcnt ====
+
+How many times to process data on one connection, before proceeding.
+Without limit, one connection with big resultset can stall pgbouncer
+for a long time.  One loop processes one `pkt_buf` amount of data.
+0 means no limit.
+
+Default: 5
+
 ==== tcp_defer_accept ====
 
 Details about following options shouldbe looked from man 7 tcp
diff --git a/include/bouncer.h b/include/bouncer.h
index e398a26..c34bc0a 100644
--- a/include/bouncer.h
+++ b/include/bouncer.h
@@ -336,6 +336,7 @@ extern int cf_pause_mode;
 extern int cf_shutdown;
 extern int cf_reboot;
 
+extern int cf_sbuf_loopcnt;
 extern int cf_sbuf_len;
 extern int cf_tcp_keepalive;
 extern int cf_tcp_keepcnt;
diff --git a/src/main.c b/src/main.c
index 98c6cd9..1973837 100644
--- a/src/main.c
+++ b/src/main.c
@@ -72,6 +72,7 @@ int cf_pool_mode = POOL_SESSION;
 
 /* sbuf config */
 int cf_sbuf_len = 2048;
+int cf_sbuf_loopcnt = 5;
 int cf_tcp_socket_buffer = 0;
 #if defined(TCP_DEFER_ACCEPT) || defined(SO_ACCEPTFILTER)
 int cf_tcp_defer_accept = 1;
@@ -154,6 +155,7 @@ ConfElem bouncer_params[] = {
 {"ignore_startup_parameters", true, CF_STR, &cf_ignore_startup_params},
 
 {"pkt_buf",		false, CF_INT, &cf_sbuf_len},
+{"sbuf_loopcnt",	true, CF_INT, &cf_sbuf_loopcnt},
 {"tcp_defer_accept",	true, {cf_get_int, set_defer_accept}, &cf_tcp_defer_accept},
 {"tcp_socket_buffer",	true, CF_INT, &cf_tcp_socket_buffer},
 {"tcp_keepalive",	true, CF_INT, &cf_tcp_keepalive},
diff --git a/src/sbuf.c b/src/sbuf.c
index 02146ad..f8dcb61 100644
--- a/src/sbuf.c
+++ b/src/sbuf.c
@@ -585,6 +585,7 @@ static bool allocate_iobuf(SBuf *sbuf)
 static void sbuf_main_loop(SBuf *sbuf, bool skip_recv)
 {
 	unsigned free, ok;
+	int loopcnt = 0;
 
 	/* sbuf was closed before in this event loop */
 	if (!sbuf->sock)
@@ -602,6 +603,13 @@ static void sbuf_main_loop(SBuf *sbuf, bool skip_recv)
 		goto skip_recv;
 
 try_more:
+	/* avoid spending too much time on single socket */
+	if (cf_sbuf_loopcnt > 0 && loopcnt >= cf_sbuf_loopcnt) {
+		log_debug("loopcnt full");
+		return;
+	}
+	loopcnt++;
+
 	/* make room in buffer */
 	sbuf_try_resync(sbuf, false);