MEDIUM: connections: Add a way to control the number of idling connections.
As by default we add all keepalive connections to the idle pool, if we run
into a pathological case, where all client don't do keepalive, but the server
does, and haproxy is configured to only reuse "safe" connections, we will
soon find ourself having lots of idling, unusable for new sessions, connections,
while we won't have any file descriptors available to create new connections.
To fix this, add 2 new global settings, "pool_low_ratio" and "pool_high_ratio".
pool-low-fd-ratio is the % of fds we're allowed to use (against the maximum
number of fds available to haproxy) before we stop adding connections to the
idle pool, and destroy them instead. The default is 20. pool-high-fd-ratio is
the % of fds we're allowed to use (against the maximum number of fds available
to haproxy) before we start killing idling connection in the event we have to
create a new outgoing connection, and no reuse is possible. The default is 25.
diff --git a/src/backend.c b/src/backend.c
index abe7308..40ce949 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -1338,6 +1338,39 @@
reuse = 0;
}
}
+ if ((!reuse || (srv_conn && !(srv_conn->flags & CO_FL_CONNECTED)))
+ && ha_used_fds > global.tune.pool_high_count) {
+ struct connection *tokill_conn;
+
+ /* We can't reuse a connection, and e have more FDs than deemd
+ * acceptable, attempt to kill an idling connection
+ */
+ /* First, try from our own idle list */
+ tokill_conn = LIST_POP_LOCKED(&srv->idle_orphan_conns[tid],
+ struct connection *, list);
+ if (tokill_conn)
+ tokill_conn->mux->destroy(tokill_conn->ctx);
+ /* If not, iterate over other thread's idling pool, and try to grab one */
+ else {
+ int i;
+
+ for (i = 0; i < global.nbthread; i++) {
+ if (i == tid)
+ continue;
+ tokill_conn = LIST_POP_LOCKED(&srv->idle_orphan_conns[i],
+ struct connection *, list);
+ if (tokill_conn) {
+ /* We got one, put it into the concerned thread's to kill list, and wake it's kill task */
+
+ LIST_ADDQ_LOCKED(&toremove_connections[i],
+ &tokill_conn->list);
+ task_wakeup(idle_conn_cleanup[i], TASK_WOKEN_OTHER);
+ break;
+ }
+ }
+ }
+
+ }
/* If we're really reusing the connection, remove it from the orphan
* list and add it back to the idle list.
*/