[MEDIUM] add support for "maxqueue" to limit server queue overload

This patch adds the "maxqueue" parameter to the server. This allows new
sessions to be immediately rebalanced when the server's queue is filled.
It's useful when session stickiness is just a performance boost (even a
huge one) but not a requirement.

This should only be used if session affinity isn't a hard functional
requirement but provides performance boost by keeping server-local
caches hot and compact).

Absence of 'maxqueue' option means unlimited queue. When queue gets filled
up to 'maxqueue' client session is moved from server-local queue to a global
one.

diff --git a/doc/haproxy-en.txt b/doc/haproxy-en.txt
index 09d311e52e6ca3669f9eb861e6f2d68398aae97a..3e8ce107b59319b18a43d7fb51788bd42ec48db0 100644 (file)
--- a/doc/haproxy-en.txt
+++ b/doc/haproxy-en.txt
@@ -1364,6 +1364,21 @@ simultaneous sessions when the proxy instance will reach 10000 sessions, and
 will receive only 10 simultaneous sessions when the proxy will be under 1000
 sessions.
 
+It is possible to limit server queue length in order to rebalance excess
+sessions between less busy application servers IF session affinity isn't
+hard functional requirement (for example it just gives huge performance boost
+by keeping server-local caches hot and compact). 'maxqueue' option sets a
+queue limit on a server, as in example below:
+
+... (just the same as in example above)
+        server pentium3-800 192.168.1.1:80 cookie s1 weight  8 minconn 10 maxconn 100 check maxqueue 50
+        server opteron-2.0G 192.168.1.2:80 cookie s2 weight 20 minconn 30 maxconn 300 check maxqueue 200
+        server opteron-2.4G 192.168.1.3:80 cookie s3 weight 24 minconn 30 maxconn 300 check
+
+Absence of 'maxqueue' option means unlimited queue. When queue gets filled
+up to 'maxqueue' client session is moved from server-local queue to a global
+one.
+
 Notes :
 -------
   - The requests will not stay indefinitely in the queue, they follow the

diff --git a/doc/haproxy-fr.txt b/doc/haproxy-fr.txt
index d29259fc7c71dc18070e6fc2ad676366a7a7ada5..7974546bf4cd23f2f0b52739be7ad896ec850ca3 100644 (file)
--- a/doc/haproxy-fr.txt
+++ b/doc/haproxy-fr.txt
@@ -1391,6 +1391,23 @@ connexions simultan
 recevra seulement 10 connexions simultanées tant que le proxy sera sous les 1000
 sessions.
 
+Il est possible de limiter la taille de la file d'attente dans le but de
+redistribuer les connexions destinées à un serveur en particulier qui sont trop
+loin pour avoir une chance d'être servies en un temps raisonnable. Ceci n'est
+acceptable que dans le cas où l'affinité entre le client et le serveur n'est
+pas obligatoire, mais motivée uniquement par des raisons de performances, par
+exemple, par l'utilisation d'un cache local au serveur. L'option 'maxqueue'
+permet de préciser la limite par serveur, tel que dans l'exemple ci-dessous :
+
+... (même exemple que précédemment)
+        server pentium3-800 192.168.1.1:80 cookie s1 weight  8 minconn 10 maxconn 100 check maxqueue 50
+        server opteron-2.0G 192.168.1.2:80 cookie s2 weight 20 minconn 30 maxconn 300 check maxqueue 200
+        server opteron-2.4G 192.168.1.3:80 cookie s3 weight 24 minconn 30 maxconn 300 check
+
+En l'absence du paramètre 'maxqueue', la file d'un serveur n'a pas de limite
+définie. Dans le cas contraire, lorsque la file atteint la limite fixée par
+'maxqueue', les clients sont déplacés vers la file globale.
+
 Notes :
 -------
   - la requête ne restera pas indéfiniment en file d'attente, elle est

diff --git a/include/types/server.h b/include/types/server.h
index 62179f33d89de96b91ca93df8ffe61f18d564808..6e3a9138b450569e5f1a551bd52faddd4a253cf8 100644 (file)
--- a/include/types/server.h
+++ b/include/types/server.h
@@ -64,6 +64,7 @@ struct server {
        int cur_sess, cur_sess_max;             /* number of currently active sessions (including syn_sent) */
        unsigned maxconn, minconn;              /* max # of active sessions (0 = unlimited), min# for dynamic limit. */
        int nbpend, nbpend_max;                 /* number of pending connections */
+       int maxqueue;                           /* maximum number of pending connections allowed */
        struct list pendconns;                  /* pending connections */
        struct task *queue_mgt;                 /* the task associated to the queue processing */
 

diff --git a/src/backend.c b/src/backend.c
index 596d5676cafffdf428815d9e57fcf957b753308e..faf5db89a9cee80ab033dc50d8ae64a33c3b050e 100644 (file)
--- a/src/backend.c
+++ b/src/backend.c
@@ -294,19 +294,25 @@ int assign_server_and_queue(struct session *s)
                return SRV_STATUS_INTERNAL;
 
        if (s->flags & SN_ASSIGNED) {
-               /* a server does not need to be assigned, perhaps because we're in
-                * direct mode, or in dispatch or transparent modes where the server
-                * is not needed.
-                */
-               if (s->srv &&
-                   s->srv->maxconn && s->srv->cur_sess >= srv_dynamic_maxconn(s->srv)) {
-                       p = pendconn_add(s);
-                       if (p)
-                               return SRV_STATUS_QUEUED;
-                       else
-                               return SRV_STATUS_FULL;
+               if (s->srv && s->srv->maxqueue > 0 && s->srv->nbpend >= s->srv->maxqueue) {
+                       s->flags &= ~(SN_DIRECT | SN_ASSIGNED | SN_ADDR_SET);
+                       s->srv = NULL;
+                       http_flush_cookie_flags(&s->txn);
+               } else {
+                       /* a server does not need to be assigned, perhaps because we're in
+                        * direct mode, or in dispatch or transparent modes where the server
+                        * is not needed.
+                        */
+                       if (s->srv &&
+                           s->srv->maxconn && s->srv->cur_sess >= srv_dynamic_maxconn(s->srv)) {
+                               p = pendconn_add(s);
+                               if (p)
+                                       return SRV_STATUS_QUEUED;
+                               else
+                                       return SRV_STATUS_FULL;
+                       }
+                       return SRV_STATUS_OK;
                }
-               return SRV_STATUS_OK;
        }
 
        /* a server needs to be assigned */

diff --git a/src/cfgparse.c b/src/cfgparse.c
index 7b73e0bee1959ee8ab1ea0a6f8fe8f29987f521b..89c8c1997ff881efce6db40637b3131a163ca06c 100644 (file)
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -1413,6 +1413,7 @@ int cfg_parse_listen(const char *file, int linenum, char **args)
                newsrv->fall = DEF_FALLTIME;
                newsrv->health = newsrv->rise; /* up, but will fall down at first failure */
                newsrv->uweight = 1;
+               newsrv->maxqueue = 0;
 
                cur_arg = 3;
                while (*args[cur_arg]) {
@@ -1465,6 +1466,10 @@ int cfg_parse_listen(const char *file, int linenum, char **args)
                                newsrv->maxconn = atol(args[cur_arg + 1]);
                                cur_arg += 2;
                        }
+                       else if (!strcmp(args[cur_arg], "maxqueue")) {
+                               newsrv->maxqueue = atol(args[cur_arg + 1]);
+                               cur_arg += 2;
+                       }
                        else if (!strcmp(args[cur_arg], "check")) {
                                global.maxsock++;
                                do_check = 1;
@@ -1521,7 +1526,7 @@ int cfg_parse_listen(const char *file, int linenum, char **args)
                        }
 #endif
                        else {
-                               Alert("parsing [%s:%d] : server %s only supports options 'backup', 'cookie', 'check', 'inter', 'rise', 'fall', 'addr', 'port', 'source', 'minconn', 'maxconn' and 'weight'.\n",
+                               Alert("parsing [%s:%d] : server %s only supports options 'backup', 'cookie', 'check', 'inter', 'rise', 'fall', 'addr', 'port', 'source', 'minconn', 'maxconn', 'maxqueue', and 'weight'.\n",
                                      file, linenum, newsrv->id);
                                return -1;
                        }

diff --git a/src/dumpstats.c b/src/dumpstats.c
index 7ec4b565be0a2cf8f08f4bd8c74275f767498d14..4d34c474a11f58d80580ad9fa5b86d25438c3ef1 100644 (file)
--- a/src/dumpstats.c
+++ b/src/dumpstats.c
@@ -372,7 +372,7 @@ int stats_dump_http(struct session *s, struct uri_auth *uri, int flags)
                             "ereq,econ,eresp,"
                             "wretr,wredis,"
                             "status,weight,act,bck,"
-                            "chkfail,chkdown,lastchg,downtime,"
+                            "chkfail,chkdown,lastchg,downtime,qlimit,"
                             "\n");
                }
                if (buffer_write_chunk(rep, &msg) != 0)
@@ -582,20 +582,20 @@ int stats_dump_proxy(struct session *s, struct proxy *px, struct uri_auth *uri,
                if (flags & STAT_FMT_HTML) {
                        /* print a new table */
                        chunk_printf(&msg, sizeof(trash),
-                                    "<table cols=\"23\" class=\"tbl\" width=\"100%%\">\n"
+                                    "<table cols=\"24\" class=\"tbl\" width=\"100%%\">\n"
                                     "<tr align=\"center\" class=\"titre\">"
                                     "<th colspan=2 class=\"pxname\">%s</th>"
                                     "<th colspan=21 class=\"empty\"></th>"
                                     "</tr>\n"
                                     "<tr align=\"center\" class=\"titre\">"
                                     "<th rowspan=2></th>"
-                                    "<th colspan=2>Queue</th><th colspan=4>Sessions</th>"
+                                    "<th colspan=3>Queue</th><th colspan=4>Sessions</th>"
                                     "<th colspan=2>Bytes</th><th colspan=2>Denied</th>"
                                     "<th colspan=3>Errors</th><th colspan=2>Warnings</th>"
                                     "<th colspan=7>Server</th>"
                                     "</tr>\n"
                                     "<tr align=\"center\" class=\"titre\">"
-                                    "<th>Cur</th><th>Max</th><th>Cur</th><th>Max</th>"
+                                    "<th>Cur</th><th>Max</th><th>Limit</th><th>Cur</th><th>Max</th>"
                                     "<th>Limit</th><th>Cumul</th><th>In</th><th>Out</th>"
                                     "<th>Req</th><th>Resp</th><th>Req</th><th>Conn</th>"
                                     "<th>Resp</th><th>Retr</th><th>Redis</th>"
@@ -617,7 +617,7 @@ int stats_dump_proxy(struct session *s, struct proxy *px, struct uri_auth *uri,
                        if (flags & STAT_FMT_HTML) {
                                chunk_printf(&msg, sizeof(trash),
                                     /* name, queue */
-                                    "<tr align=center class=\"frontend\"><td>Frontend</td><td colspan=2></td>"
+                                    "<tr align=center class=\"frontend\"><td>Frontend</td><td colspan=3></td>"
                                     /* sessions : current, max, limit, cumul */
                                     "<td align=right>%d</td><td align=right>%d</td>"
                                     "<td align=right>%d</td><td align=right>%d</td>"
@@ -657,7 +657,7 @@ int stats_dump_proxy(struct session *s, struct proxy *px, struct uri_auth *uri,
                                     /* server status : reflect frontend status */
                                     "%s,"
                                     /* rest of server: nothing */
-                                    ",,,,,,,"
+                                    ",,,,,,,,"
                                     "\n",
                                     px->id,
                                     px->feconn, px->feconn_max, px->maxconn, px->cum_feconn,
@@ -709,8 +709,8 @@ int stats_dump_proxy(struct session *s, struct proxy *px, struct uri_auth *uri,
                                chunk_printf(&msg, sizeof(trash),
                                     /* name */
                                     "<tr align=\"center\" class=\"%s%d\"><td>%s</td>"
-                                    /* queue : current, max */
-                                    "<td align=right>%d</td><td align=right>%d</td>"
+                                    /* queue : current, max, limit */
+                                    "<td align=right>%d</td><td align=right>%d</td><td align=right>%s</td>"
                                     /* sessions : current, max, limit, cumul */
                                     "<td align=right>%d</td><td align=right>%d</td>"
                                     "<td align=right>%s</td><td align=right>%d</td>"
@@ -725,8 +725,8 @@ int stats_dump_proxy(struct session *s, struct proxy *px, struct uri_auth *uri,
                                     "",
                                     (sv->state & SRV_BACKUP) ? "backup" : "active",
                                     sv_state, sv->id,
-                                    sv->nbpend, sv->nbpend_max,
-                                    sv->cur_sess, sv->cur_sess_max, sv->maxconn ? ultoa(sv->maxconn) : "-", sv->cum_sess,
+                                    sv->nbpend, sv->nbpend_max, LIM2A0(sv->maxqueue, "-"),
+                                    sv->cur_sess, sv->cur_sess_max, LIM2A1(sv->maxconn, "-"), sv->cum_sess,
                                     sv->bytes_in, sv->bytes_out,
                                     sv->failed_secu,
                                     sv->failed_conns, sv->failed_resp,
@@ -809,12 +809,17 @@ int stats_dump_proxy(struct session *s, struct proxy *px, struct uri_auth *uri,
                                /* check failures: unique, fatal; last change, total downtime */
                                if (sv->state & SRV_CHECKED)
                                        chunk_printf(&msg, sizeof(trash),
-                                            "%d,%d,%d,%d,\n",
+                                            "%d,%d,%d,%d,",
                                             sv->failed_checks, sv->down_trans,
                                             now.tv_sec - sv->last_change, srv_downtime(sv));
                                else
                                        chunk_printf(&msg, sizeof(trash),
-                                            ",,,,\n");
+                                            ",,,,");
+
+                               /* queue limit and EOL */
+                               chunk_printf(&msg, sizeof(trash),
+                                    "%s,\n",
+                                    LIM2A0(sv->maxqueue, ""));
                        }
                        if (buffer_write_chunk(rep, &msg) != 0)
                                return 0;
@@ -845,7 +850,7 @@ int stats_dump_proxy(struct session *s, struct proxy *px, struct uri_auth *uri,
                                     /* name */
                                     "<tr align=center class=\"backend\"><td>Backend</td>"
                                     /* queue : current, max */
-                                    "<td align=right>%d</td><td align=right>%d</td>"
+                                    "<td align=right>%d</td><td align=right>%d</td><td></td>"
                                     /* sessions : current, max, limit, cumul. */
                                     "<td align=right>%d</td><td align=right>%d</td><td align=right>%d</td><td align=right>%d</td>"
                                     /* bytes : in, out */
@@ -903,7 +908,7 @@ int stats_dump_proxy(struct session *s, struct proxy *px, struct uri_auth *uri,
                                     "%d,%d,%d,"
                                     /* rest of backend: nothing, down transformations,
                                      * last change, total downtime. */
-                                    ",%d,%d,%d,"
+                                    ",%d,%d,%d,,"
                                     "\n",
                                     px->id,
                                     px->nbpend /* or px->totpend ? */, px->nbpend_max,