From 922a80607531e086e9e54a38b19ecd3b1ac46ce4 Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Thu, 4 Dec 2008 09:33:58 +0100 Subject: [PATCH] [BUG] do not dequeue the backend's pending connections on a dead server Kai Krueger found that previous patch was incomplete, because there is an unconditionnal call to process_srv_queue() in session_free() which still causes a dead server to consume pending connections from the backend. This call was made unconditionnal so that we don't leave unserved connections in the server queue, for instance connections coming in with "option persist" which can bypass the server status check. However, the server must not touch the backend's queue if it is down. Another fear was that some connections might remain unserved when the server is using a dynamic maxconn if the number of connections to the backend is too low. Right now, srv_dynamic_maxconn() ensures this cannot happen, so the call can remain conditionnal. The fix consists in allowing a server to process it own queue whatever its state, but not to touch the backend's queue if it is down. Its queue should normally be empty when the server is down because it is redistributed when the server goes down. The only remaining cases are precisely the persistent connections with "option persist" set, coming in after the queue has been redispatched. Those ones must still be processed when a connection terminates. (cherry picked from commit cd485c44807bfcdb4928dd83c1907636b4e1b6f3) --- include/proto/queue.h | 6 +++--- src/queue.c | 6 +++++- src/session.c | 5 ++++- 3 files changed, 12 insertions(+), 5 deletions(-) diff --git a/include/proto/queue.h b/include/proto/queue.h index be78b53561..77964feb37 100644 --- a/include/proto/queue.h +++ b/include/proto/queue.h @@ -64,11 +64,11 @@ static inline struct pendconn *pendconn_from_px(const struct proxy *px) { } /* returns 0 if nothing has to be done for server regarding queued connections, - * and non-zero otherwise. If the server is down, we always return zero. Suited for - * and if/else usage. + * and non-zero otherwise. If the server is down, we only check its own queue. Suited + * for and if/else usage. */ static inline int may_dequeue_tasks(const struct server *s, const struct proxy *p) { - return (s && (s->state & SRV_RUNNING) && (s->nbpend || p->nbpend) && + return (s && (s->nbpend || (p->nbpend && (s->state & SRV_RUNNING))) && (!s->maxconn || s->cur_sess < srv_dynamic_maxconn(s))); } diff --git a/src/queue.c b/src/queue.c index 172e0560d0..fe94043643 100644 --- a/src/queue.c +++ b/src/queue.c @@ -86,6 +86,10 @@ void process_srv_queue(struct server *s) * returned. Note that neither nor may be NULL. * Priority is given to the oldest request in the queue if both and * have pending requests. This ensures that no request will be left unserved. + * The queue is not considered if the server is not RUNNING. The + * queue is still considered in this case, because if some connections remain + * there, it means that some requests have been forced there after it was seen + * down (eg: due to option persist). * The session is immediately marked as "assigned", and both its and * are set to , */ @@ -97,7 +101,7 @@ struct session *pendconn_get_next_sess(struct server *srv, struct proxy *px) ps = pendconn_from_srv(srv); pp = pendconn_from_px(px); /* we want to get the definitive pendconn in */ - if (!pp) { + if (!pp || !(srv->state & SRV_RUNNING)) { if (!ps) return NULL; } else { diff --git a/src/session.c b/src/session.c index c0df6c6850..5046e04264 100644 --- a/src/session.c +++ b/src/session.c @@ -46,13 +46,16 @@ void session_free(struct session *s) if (s->pend_pos) pendconn_free(s->pend_pos); + if (s->srv) { /* there may be requests left pending in queue */ if (s->flags & SN_CURR_SESS) { s->flags &= ~SN_CURR_SESS; s->srv->cur_sess--; } - process_srv_queue(s->srv); + if (may_dequeue_tasks(s->srv, s->be)) + process_srv_queue(s->srv); } + if (unlikely(s->srv_conn)) { /* the session still has a reserved slot on a server, but * it should normally be only the same as the one above, -- 2.39.5