diff --git a/ROADMAP b/ROADMAP
index 8dae1ab49..b70024e93 100644
--- a/ROADMAP
+++ b/ROADMAP
@@ -30,7 +30,7 @@
and might cause little trouble to some very specific clients used to
close immediately after sending the request (no support for KA, which ones?)
- - minconn : makes the server's maxconn dynamic, which will be computed as a
+ + minconn : makes the server's maxconn dynamic, which will be computed as a
ratio of the proxy's sessions :
srv->effective_maxconn =
max(srv->maxconn * px->nbsess / px->maxconn, srv->minconn)
diff --git a/doc/haproxy-en.txt b/doc/haproxy-en.txt
index 2f9660e59..191f136f5 100644
--- a/doc/haproxy-en.txt
+++ b/doc/haproxy-en.txt
@@ -1216,6 +1216,41 @@ Example :
server web-backup1 192.168.2.1:80 cookie s4 check maxconn 200 backup
server web-excuse 192.168.3.1:80 check backup
+
+This was so much efficient at reducing the server's response time that some
+users wanted to use low values to improve their server's performance. However,
+they were not able anymore to handle very large loads because it was not
+possible anymore to saturate the servers. For this reason, version 1.2.14 has
+brought dynamic limitation with the addition of the parameter 'minconn'. When
+this parameter is set along with maxconn, it will enable dynamic limitation
+based on the instance's load. The maximum number of concurrent sessions on a
+server will be proportionnal to the number of sessions on the instance relative
+to its maxconn. A minimum of <minconn> will be allowed whatever the load. This
+will ensure that servers will perform at their best level under normal loads,
+while still handling surges when needed. The dynamic limit is computed like
+this :
+
+ srv.dyn_limit = max(srv.minconn, srv.maxconn * inst.sess / inst.maxconn)
+
+Example :
+---------
+ # be nice with P3 which only has 256 MB of RAM.
+ listen web_appl 0.0.0.0:80
+ maxconn 10000
+ mode http
+ cookie SERVERID insert nocache indirect
+ balance roundrobin
+ server pentium3-800 192.168.1.1:80 cookie s1 weight 8 minconn 10 maxconn 100 check
+ server opteron-2.0G 192.168.1.2:80 cookie s2 weight 20 minconn 30 maxconn 300 check
+ server opteron-2.4G 192.168.1.3:80 cookie s3 weight 24 minconn 30 maxconn 300 check
+ server web-backup1 192.168.2.1:80 cookie s4 check maxconn 200 backup
+ server web-excuse 192.168.3.1:80 check backup
+
+In the example above, the server 'pentium3-800' will receive at most 100
+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.
+
Notes :
-------
- The requests will not stay indefinitely in the queue, they follow the
@@ -1223,6 +1258,8 @@ Notes :
timeout because the server is saturated or because the queue is filled,
the session will expire with a 503 error.
+ - if only <minconn> is specified, it has the same effect as <maxconn>
+
- setting too low values for maxconn might improve performance but might also
allow slow users to block access to the server for other users.
diff --git a/haproxy.c b/haproxy.c
index c6a03125b..586978a0a 100644
--- a/haproxy.c
+++ b/haproxy.c
@@ -587,7 +587,7 @@ struct server {
unsigned int wscore; /* weight score, used during srv map computation */
int cur_sess, cur_sess_max; /* number of currently active sessions (including syn_sent) */
unsigned int cum_sess; /* cumulated number of sessions really sent to this server */
- unsigned int maxconn; /* max # of active sessions. 0 = unlimited. */
+ unsigned int maxconn, minconn; /* max # of active sessions (0 = unlimited), min# for dynamic limit. */
unsigned failed_checks, down_trans; /* failed checks and up-down transitions */
unsigned failed_conns, failed_resp; /* failed connect() and responses */
unsigned failed_secu; /* blocked responses because of security concerns */
@@ -695,9 +695,9 @@ struct proxy {
struct list pendconns; /* pending connections with no server assigned yet */
int nbpend, nbpend_max; /* number of pending connections with no server assigned yet */
int totpend; /* total number of pending connections on this instance (for stats) */
- int nbconn, nbconn_max; /* # of active sessions */
+ unsigned int nbconn, nbconn_max; /* # of active sessions */
unsigned int cum_conn; /* cumulated number of processed sessions */
- int maxconn; /* max # of active sessions */
+ unsigned int maxconn; /* max # of active sessions */
unsigned failed_conns, failed_resp; /* failed connect() and responses */
unsigned failed_secu; /* blocked responses because of security concerns */
int conn_retries; /* maximum number of connect retries */
@@ -1983,12 +1983,22 @@ static struct pendconn *pendconn_add(struct session *sess) {
return p;
}
+/* returns the effective dynamic maxconn for a server, considering the minconn
+ * and the proxy's usage relative to its saturation.
+ */
+static unsigned int srv_dynamic_maxconn(struct server *s) {
+ return s->minconn ?
+ ((s->maxconn * s->proxy->nbconn / s->proxy->maxconn) < s->minconn) ? s->minconn :
+ (s->maxconn * s->proxy->nbconn / s->proxy->maxconn) : s->maxconn;
+}
+
/* returns 0 if nothing has to be done for server <s> regarding queued connections,
* and non-zero otherwise. Suited for and if/else usage.
*/
static inline int may_dequeue_tasks(struct server *s, struct proxy *p) {
return (s && (s->nbpend || p->nbpend) &&
- s->maxconn && s->cur_sess < s->maxconn && s->queue_mgt);
+ (!s->maxconn || s->cur_sess < srv_dynamic_maxconn(s)) &&
+ s->queue_mgt);
}
@@ -2157,7 +2167,7 @@ static inline struct server *get_server_rr_with_conns(struct proxy *px) {
do {
srv = px->srv_map[newidx++];
- if (!srv->maxconn || srv->cur_sess < srv->maxconn) {
+ if (!srv->maxconn || srv->cur_sess < srv_dynamic_maxconn(srv)) {
px->srv_rr_idx = newidx;
return srv;
}
@@ -2349,7 +2359,7 @@ int assign_server_and_queue(struct session *s) {
* is not needed.
*/
if (s->srv &&
- s->srv->maxconn && s->srv->cur_sess >= s->srv->maxconn) {
+ s->srv->maxconn && s->srv->cur_sess >= srv_dynamic_maxconn(s->srv)) {
p = pendconn_add(s);
if (p)
return SRV_STATUS_QUEUED;
@@ -2364,8 +2374,8 @@ int assign_server_and_queue(struct session *s) {
switch (err) {
case SRV_STATUS_OK:
/* in balance mode, we might have servers with connection limits */
- if (s->srv != NULL &&
- s->srv->maxconn && s->srv->cur_sess >= s->srv->maxconn) {
+ 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;
@@ -6737,7 +6747,7 @@ int process_chk(struct task *t) {
/* check if we can handle some connections queued at the proxy. We
* will take as many as we can handle.
*/
- for (xferred = 0; !s->maxconn || xferred < s->maxconn; xferred++) {
+ for (xferred = 0; !s->maxconn || xferred < srv_dynamic_maxconn(s); xferred++) {
struct session *sess;
struct pendconn *p;
@@ -6810,7 +6820,7 @@ int process_srv_queue(struct task *t) {
/* First, check if we can handle some connections queued at the proxy. We
* will take as many as we can handle.
*/
- for (xferred = 0; s->cur_sess + xferred < s->maxconn; xferred++) {
+ for (xferred = 0; s->cur_sess + xferred < srv_dynamic_maxconn(s); xferred++) {
struct session *sess;
sess = pendconn_get_next_sess(s, p);
@@ -8556,6 +8566,10 @@ int cfg_parse_listen(char *file, int linenum, char **args) {
newsrv->uweight = w - 1;
cur_arg += 2;
}
+ else if (!strcmp(args[cur_arg], "minconn")) {
+ newsrv->minconn = atol(args[cur_arg + 1]);
+ cur_arg += 2;
+ }
else if (!strcmp(args[cur_arg], "maxconn")) {
newsrv->maxconn = atol(args[cur_arg + 1]);
cur_arg += 2;
@@ -8576,7 +8590,7 @@ int cfg_parse_listen(char *file, int linenum, char **args) {
cur_arg += 2;
}
else {
- Alert("parsing [%s:%d] : server %s only supports options 'backup', 'cookie', 'check', 'inter', 'rise', 'fall', 'port', 'source', and 'weight'.\n",
+ Alert("parsing [%s:%d] : server %s only supports options 'backup', 'cookie', 'check', 'inter', 'rise', 'fall', 'port', 'source', 'minconn', 'maxconn' and 'weight'.\n",
file, linenum, newsrv->id);
return -1;
}
@@ -9451,6 +9465,12 @@ int readcfgfile(char *file) {
*/
newsrv = curproxy->srv;
while (newsrv != NULL) {
+ if (newsrv->minconn && !newsrv->maxconn) {
+ /* only 'minconn' was specified. Let's turn this into maxconn */
+ newsrv->maxconn = newsrv->minconn;
+ newsrv->minconn = 0;
+ }
+
if (newsrv->maxconn > 0) {
struct task *t;