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MEDIUM: backend: remove impossible cases from connect_server()

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Now that we start by releasing any possibly existing connection,
the conditions simplify a little bit and some of the complex cases
can be removed. A few comments were also added for non-obvious cases.
This commit is contained in:
Willy Tarreau 2019-07-18 19:26:11 +02:00
parent a5797aab11
commit b082186528
1 changed files with 40 additions and 47 deletions
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87
src/backend.c
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@ -1143,6 +1143,7 @@ int connect_server(struct stream *s)
struct connection *srv_conn = NULL;
struct connection *old_conn = NULL;
struct conn_stream *srv_cs = NULL;
struct sess_srv_list *srv_list;
struct server *srv;
int reuse = 0;
int reuse_orphan = 0;
@ -1156,52 +1157,39 @@ int connect_server(struct stream *s)
*/
si_release_endpoint(&s->si[1]);
if (!srv_cs)
srv_conn = objt_conn(s->si[1].end);
else
srv_conn = cs_conn(srv_cs);
if (srv_conn) {
if (!srv_conn->target || srv_conn->target == s->target) {
srv_conn->flags &= ~(CO_FL_ERROR | CO_FL_SOCK_RD_SH | CO_FL_SOCK_WR_SH);
if (srv_cs)
srv_cs->flags &= ~(CS_FL_ERROR | CS_FL_EOS);
reuse = 1;
old_conn = srv_conn;
} else {
srv_conn = NULL;
srv_cs = NULL;
si_release_endpoint(&s->si[1]);
}
}
if (!old_conn) {
struct sess_srv_list *srv_list;
list_for_each_entry(srv_list, &s->sess->srv_list, srv_list) {
if (srv_list->target == s->target) {
list_for_each_entry(srv_conn, &srv_list->conn_list,
session_list) {
if (conn_xprt_ready(srv_conn) &&
srv_conn->mux && (srv_conn->mux->avail_streams(srv_conn) > 0)) {
reuse = 1;
break;
}
/* first, search for a matching connection in the session's idle conns */
list_for_each_entry(srv_list, &s->sess->srv_list, srv_list) {
if (srv_list->target == s->target) {
list_for_each_entry(srv_conn, &srv_list->conn_list, session_list) {
if (conn_xprt_ready(srv_conn) &&
srv_conn->mux && (srv_conn->mux->avail_streams(srv_conn) > 0)) {
reuse = 1;
break;
}
break;
}
}
if (reuse == 0) {
srv_conn = NULL;
if (!LIST_ISEMPTY(&s->sess->srv_list)) {
srv_list = LIST_ELEM(s->sess->srv_list.n,
struct sess_srv_list *, srv_list);
if (!LIST_ISEMPTY(&srv_list->conn_list))
srv_conn = LIST_ELEM(srv_list->conn_list.n,
struct connection *, session_list);
}
break;
}
}
if (!reuse) {
/* no connection was found in our session's list. Pick any
* random one that we could trade against another one.
*/
srv_conn = NULL;
if (!LIST_ISEMPTY(&s->sess->srv_list)) {
srv_list = LIST_ELEM(s->sess->srv_list.n, struct sess_srv_list *, srv_list);
if (!LIST_ISEMPTY(&srv_list->conn_list))
srv_conn = LIST_ELEM(srv_list->conn_list.n, struct connection *, session_list);
}
}
/* OK at this point we have this :
* - srv_conn points to an existing connection or NULL
* - if reuse is set, srv_conn holds a valid connection, otherwise it
* points to any of our old connections we may want to trade against
* another one
*/
old_conn = srv_conn;
srv = objt_server(s->target);
@ -1222,6 +1210,9 @@ int connect_server(struct stream *s)
* ----+-----+-----+ ----+-----+-----+ ----+-----+-----+
* idle| - | 1 | idle| - | 1 | idle| 2 | 1 |
* ----+-----+-----+ ----+-----+-----+ ----+-----+-----+
*
* Idle conns are necessarily looked up on the same thread so
* that there is no concurrency issues.
*/
if (srv->idle_conns && !LIST_ISEMPTY(&srv->idle_conns[tid]) &&
((s->be->options & PR_O_REUSE_MASK) != PR_O_REUSE_NEVR &&
@ -1256,6 +1247,10 @@ int connect_server(struct stream *s)
reuse = 1;
}
/* here reuse might have been set above, indicating srv_conn finally
* is OK.
*/
if (reuse) {
/* Disable connection reuse if a dynamic source is used.
* As long as we don't share connections between servers,
@ -1271,6 +1266,7 @@ int connect_server(struct stream *s)
reuse = 0;
}
}
if (((!reuse || (srv_conn && !(srv_conn->flags & CO_FL_CONNECTED)))
&& ha_used_fds > global.tune.pool_high_count) && srv->idle_orphan_conns) {
struct connection *tokill_conn;
@ -1333,7 +1329,7 @@ int connect_server(struct stream *s)
}
/* We're about to use another connection, let the mux know we're
* done with this one
* done with this one.
*/
if (old_conn != srv_conn && old_conn && reuse && !reuse_orphan) {
struct session *sess = srv_conn->owner;
@ -1356,10 +1352,7 @@ int connect_server(struct stream *s)
}
if (reuse) {
/* We already created a cs earlier when using http_proxy, so
* only create a new one if we don't have one already.
*/
if (!srv_cs && srv_conn->mux) {
if (srv_conn->mux) {
int avail = srv_conn->mux->avail_streams(srv_conn);
if (avail <= 1) {