BUG/MEDIUM: zero-weight servers must not dequeue requests from the backend
It was reported that a server configured with a zero weight would
sometimes still take connections from the backend queue. This issue is
real, it happens this way :
1) the disabled server accepts a request with a cookie
2) many cookie-less requests accumulate in the backend queue
3) when the disabled server completes its request, it checks its own
queue and the backend's queue
4) the server takes a pending request from the backend queue and
processes it. In response, the server's cookie is assigned to
the client, which ensures that some requests will continue to
be served by this server, leading back to point 1 above.
The fix consists in preventing a zero-weight server from dequeuing pending
requests from the backend. Making use of srv_is_usable() in such tests makes
the tests more robust against future changes.
This fix must be backported to 1.4 and 1.3.
diff --git a/include/proto/queue.h b/include/proto/queue.h
index 77964fe..7bf8137 100644
--- a/include/proto/queue.h
+++ b/include/proto/queue.h
@@ -1,23 +1,23 @@
/*
- include/proto/queue.h
- This file defines everything related to queues.
-
- Copyright (C) 2000-2008 Willy Tarreau - w@1wt.eu
-
- This library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation, version 2.1
- exclusively.
-
- This library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public
- License along with this library; if not, write to the Free Software
- Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
-*/
+ * include/proto/queue.h
+ * This file defines everything related to queues.
+ *
+ * Copyright (C) 2000-2012 Willy Tarreau - w@1wt.eu
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation, version 2.1
+ * exclusively.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
#ifndef _PROTO_QUEUE_H
#define _PROTO_QUEUE_H
@@ -32,6 +32,8 @@
#include <types/server.h>
#include <types/task.h>
+#include <proto/backend.h>
+
extern struct pool_head *pool2_pendconn;
int init_pendconn();
@@ -68,7 +70,7 @@
* for and if/else usage.
*/
static inline int may_dequeue_tasks(const struct server *s, const struct proxy *p) {
- return (s && (s->nbpend || (p->nbpend && (s->state & SRV_RUNNING))) &&
+ return (s && (s->nbpend || (p->nbpend && srv_is_usable(s->state, s->eweight))) &&
(!s->maxconn || s->cur_sess < srv_dynamic_maxconn(s)));
}
diff --git a/src/queue.c b/src/queue.c
index 395d752..dd6e962 100644
--- a/src/queue.c
+++ b/src/queue.c
@@ -109,7 +109,7 @@
ps = pendconn_from_srv(srv);
pp = pendconn_from_px(px);
/* we want to get the definitive pendconn in <ps> */
- if (!pp || !(rsrv->state & SRV_RUNNING) || (rsrv->state & (SRV_GOINGDOWN|SRV_MAINTAIN))) {
+ if (!pp || !srv_is_usable(rsrv->state, rsrv->eweight)) {
if (!ps)
return NULL;
} else {