From: Olivier Houchard <ohouchard@haproxy.com>
Date: Fri, 28 Dec 2018 17:50:57 +0000 (+0100)
Subject: MEDIUM: sessions: Keep track of which connections are idle.
X-Git-Tag: v2.0-dev1~308
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=a2dbeb22fcc2d2bbaaf28ed6bc4130ae3ad6d146;p=thirdparty%2Fhaproxy.git

MEDIUM: sessions: Keep track of which connections are idle.

Instead of keeping track of the number of connections we're responsible for,
keep track of the number of connections we're responsible for that we are
currently considering idling (ie that we are not using, they may be in use
by other sessions), that way we can actually reuse connections when we have
more connections than the max configured.
---

diff --git a/include/proto/connection.h b/include/proto/connection.h
index 28e7580913..79722d8c88 100644
--- a/include/proto/connection.h
+++ b/include/proto/connection.h
@@ -676,7 +676,8 @@ static inline void conn_free(struct connection *conn)
 	/* Remove ourself from the session's connections list, if any. */
 	if (!LIST_ISEMPTY(&conn->session_list)) {
 		struct session *sess = conn->owner;
-		sess->resp_conns--;
+		if (conn->flags & CO_FL_SESS_IDLE)
+			sess->idle_conns--;
 		session_unown_conn(sess, conn);
 	}
 
diff --git a/include/proto/session.h b/include/proto/session.h
index c34866d3d5..d54e9454b5 100644
--- a/include/proto/session.h
+++ b/include/proto/session.h
@@ -112,7 +112,6 @@ static inline int session_add_conn(struct session *sess, struct connection *conn
 		LIST_INIT(&srv_list->conn_list);
 		LIST_ADDQ(&sess->srv_list, &srv_list->srv_list);
 	}
-	sess->resp_conns++;
 	LIST_ADDQ(&srv_list->conn_list, &conn->session_list);
 	return 1;
 }
@@ -120,17 +119,19 @@ static inline int session_add_conn(struct session *sess, struct connection *conn
 /* Returns 0 if the session can keep the idle conn, -1 if it was destroyed, or 1 if it was added to the server list */
 static inline int session_check_idle_conn(struct session *sess, struct connection *conn)
 {
-	if (sess->resp_conns > sess->fe->max_out_conns) {
+	if (sess->idle_conns > sess->fe->max_out_conns) {
 		/* We can't keep the connection, let's try to add it to the server idle list */
 		session_unown_conn(sess, conn);
 		conn->owner = NULL;
-		sess->resp_conns--;
 		if (!srv_add_to_idle_list(objt_server(conn->target), conn)) {
 			/* The server doesn't want it, let's kill the connection right away */
 			conn->mux->destroy(conn);
 			return -1;
 		}
 		return 1;
+	} else {
+		conn->flags |= CO_FL_SESS_IDLE;
+		sess->idle_conns++;
 	}
 	return 0;
 }
diff --git a/include/types/connection.h b/include/types/connection.h
index f1fd7a09bd..b273ece460 100644
--- a/include/types/connection.h
+++ b/include/types/connection.h
@@ -196,6 +196,8 @@ enum {
 	/* This flag is used to know that a PROXY protocol header was sent by the client */
 	CO_FL_RCVD_PROXY    = 0x20000000,
 
+	/* The connection is unused by its owner */
+	CO_FL_SESS_IDLE     = 0x40000000,
 	/* unused : 0x40000000 */
 
 	/* This last flag indicates that the transport layer is used (for instance
diff --git a/include/types/session.h b/include/types/session.h
index 1675f8f964..328372d6ec 100644
--- a/include/types/session.h
+++ b/include/types/session.h
@@ -55,7 +55,7 @@ struct session {
 	struct vars vars;               /* list of variables for the session scope. */
 	struct task *task;              /* handshake timeout processing */
 	long t_handshake;               /* handshake duration, -1 = not completed */
-	int resp_conns;                 /* Number of connections we're currently responsible for */
+	int idle_conns;                 /* Number of connections we're currently responsible for that we are not using */
 	struct list srv_list;           /* List of servers and the connections the session is currently responsible for */
 };
 
diff --git a/src/backend.c b/src/backend.c
index b6f08d5e7a..3c1620bbb1 100644
--- a/src/backend.c
+++ b/src/backend.c
@@ -1240,6 +1240,13 @@ int connect_server(struct stream *s)
 		LIST_ADDQ(&srv->idle_conns[tid], &srv_conn->list);
 		if (LIST_ISEMPTY(&srv->idle_orphan_conns[tid]))
 			task_unlink_wq(srv->idle_task[tid]);
+	} else if (reuse) {
+		if (srv_conn->flags & CO_FL_SESS_IDLE) {
+			struct session *sess = srv_conn->owner;
+
+			srv_conn->flags &= ~CO_FL_SESS_IDLE;
+			sess->idle_conns--;
+		}
 	}
 
 	/* We're about to use another connection, let the mux know we're
@@ -1251,6 +1258,8 @@ int connect_server(struct stream *s)
 		if (sess) {
 			if (old_conn && !(old_conn->flags & CO_FL_PRIVATE) &&
 			    old_conn->mux != NULL) {
+				if (old_conn->flags & CO_FL_SESS_IDLE)
+					s->sess->idle_conns--;
 				session_unown_conn(s->sess, old_conn);
 				old_conn->owner = sess;
 				if (!session_add_conn(sess, old_conn, s->target)) {
diff --git a/src/session.c b/src/session.c
index 48a5d9a70a..9e95b328a6 100644
--- a/src/session.c
+++ b/src/session.c
@@ -62,7 +62,7 @@ struct session *session_new(struct proxy *fe, struct listener *li, enum obj_type
 		HA_ATOMIC_ADD(&totalconn, 1);
 		HA_ATOMIC_ADD(&jobs, 1);
 		LIST_INIT(&sess->srv_list);
-		sess->resp_conns = 0;
+		sess->idle_conns = 0;
 	}
 	return sess;
 }