From 91886b692a743a63c3f25aca65bac3f2dc7c38bd Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@1wt.eu>
Date: Wed, 7 Sep 2011 14:38:31 +0200
Subject: [PATCH] [MEDIUM] stats: add the "set maxconn" setting to the command
 line interface

This option permits to change the global maxconn setting within the
limit that was set by the initial value, which is now reported as the
hard maxconn value. This allows to immediately accept more concurrent
connections or to stop accepting new ones until the value passes below
the indicated setting.

The main use of this option is on systems where many haproxy instances
are loaded and admins need to re-adjust resource sharing at run time
to regain a bit of fairness between processes.
---
 doc/configuration.txt  |  8 ++++++++
 include/types/global.h |  2 +-
 src/dumpstats.c        | 39 +++++++++++++++++++++++++++++++++++++--
 3 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/doc/configuration.txt b/doc/configuration.txt
index 98d021e61..becdab745 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -9561,6 +9561,14 @@ set maxconn frontend <frontend> <value>
   delayed until the threshold is reached. The frontend might be specified by
   either its name or its numeric ID prefixed with a sharp ('#').
 
+set maxconn global <maxconn>
+  Dynamically change the global maxconn setting within the range defined by the
+  initial global maxconn setting. If it is increased and connections were
+  pending, they will immediately be accepted. If it is lowered to a value below
+  the current number of connections, new connections acceptation will be
+  delayed until the threshold is reached. A value of zero restores the initial
+  setting.
+
 set timeout cli <delay>
   Change the CLI interface timeout for current connection. This can be useful
   during long debugging sessions where the user needs to constantly inspect
diff --git a/include/types/global.h b/include/types/global.h
index 94e21a28b..cdd1bc478 100644
--- a/include/types/global.h
+++ b/include/types/global.h
@@ -65,7 +65,7 @@ struct global {
 	int uid;
 	int gid;
 	int nbproc;
-	int maxconn;
+	int maxconn, hardmaxconn;
 	int maxpipes;		/* max # of pipes */
 	int maxsock;		/* max # of sockets */
 	int rlimit_nofile;	/* default ulimit-n value : 0=unset */
diff --git a/src/dumpstats.c b/src/dumpstats.c
index feeb85091..c9c40557a 100644
--- a/src/dumpstats.c
+++ b/src/dumpstats.c
@@ -1020,8 +1020,42 @@ static int stats_sock_parse_request(struct stream_interface *si, char *line)
 
 				return 1;
 			}
+			else if (strcmp(args[2], "global") == 0) {
+				int v;
+
+				if (s->listener->perm.ux.level < ACCESS_LVL_ADMIN) {
+					si->applet.ctx.cli.msg = stats_permission_denied_msg;
+					si->applet.st0 = STAT_CLI_PRINT;
+					return 1;
+				}
+
+				if (!*args[3]) {
+					si->applet.ctx.cli.msg = "Expects an integer value.\n";
+					si->applet.st0 = STAT_CLI_PRINT;
+					return 1;
+				}
+
+				v = atoi(args[3]);
+				if (v > global.hardmaxconn) {
+					si->applet.ctx.cli.msg = "Value out of range.\n";
+					si->applet.st0 = STAT_CLI_PRINT;
+					return 1;
+				}
+
+				/* check for unlimited values */
+				if (v <= 0)
+					v = global.hardmaxconn;
+
+				global.maxconn = v;
+
+				/* Dequeues all of the listeners waiting for a resource */
+				if (!LIST_ISEMPTY(&global_listener_queue))
+					dequeue_all_listeners(&global_listener_queue);
+
+				return 1;
+			}
 			else {
-				si->applet.ctx.cli.msg = "'set maxconn' only supports 'frontend'.\n";
+				si->applet.ctx.cli.msg = "'set maxconn' only supports 'frontend' and 'global'.\n";
 				si->applet.st0 = STAT_CLI_PRINT;
 				return 1;
 			}
@@ -1393,6 +1427,7 @@ static int stats_dump_raw_to_buffer(struct stream_interface *si)
 				     "Ulimit-n: %d\n"
 				     "Maxsock: %d\n"
 				     "Maxconn: %d\n"
+				     "Hard_maxconn: %d\n"
 				     "Maxpipes: %d\n"
 				     "CurrConns: %d\n"
 				     "PipesUsed: %d\n"
@@ -1409,7 +1444,7 @@ static int stats_dump_raw_to_buffer(struct stream_interface *si)
 				     up,
 				     global.rlimit_memmax,
 				     global.rlimit_nofile,
-				     global.maxsock, global.maxconn, global.maxpipes,
+				     global.maxsock, global.maxconn, global.hardmaxconn, global.maxpipes,
 				     actconn, pipes_used, pipes_free,
 				     nb_tasks_cur, run_queue_cur,
 				     global.node, global.desc?global.desc:""