BUG/MINOR: backend: use cum_sess counters instead of cum_conn

This commit is part of a serie to align counters usage between
frontends/listeners on one side and backends/servers on the other.

"stot" metric refers to the total number of sessions. On backend side,
it is interpreted as a number of streams. Previously, this was accounted
using <cum_sess> be_counters field for servers, but <cum_conn> instead
for backend proxies.

Adjust this by using <cum_sess> for both proxies and servers. As such,
<cum_conn> field can be removed from be_counters.

Note that several diagnostic messages which reports total frontend and
backend connections were adjusted to use <cum_sess>. However, this is an
outdated and misleading information as it does reports streams count on
backend side. These messages should be fixed in a separate commit.

This should be backported to all stable releases.

(cherry picked from commit c02ec9a9db205fda124a40a2a87913a0528b0e5b)
Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
(cherry picked from commit 06053bcad9735562b9eacd6e736e2d71153c665d)
Signed-off-by: Amaury Denoyelle <adenoyelle@haproxy.com>
diff --git a/include/haproxy/counters-t.h b/include/haproxy/counters-t.h
index 933c228..8ba6322 100644
--- a/include/haproxy/counters-t.h
+++ b/include/haproxy/counters-t.h
@@ -68,7 +68,6 @@
 /* counters used by servers and backends */
 struct be_counters {
 	unsigned int conn_max;                  /* max # of active sessions */
-	long long    cum_conn;                  /* cumulated number of received connections */
 	long long    cum_sess;                  /* cumulated number of accepted connections */
 	long long  cum_lbconn;                  /* cumulated number of sessions processed by load balancing (BE only) */
 	unsigned long last_sess;                /* last session time */
diff --git a/include/haproxy/proxy.h b/include/haproxy/proxy.h
index 39a4637..f5c096c 100644
--- a/include/haproxy/proxy.h
+++ b/include/haproxy/proxy.h
@@ -163,10 +163,10 @@
 		_HA_ATOMIC_INC(&l->counters->cum_sess_ver[http_ver - 1]);
 }
 
-/* increase the number of cumulated connections on the designated backend */
+/* increase the number of cumulated streams on the designated backend */
 static inline void proxy_inc_be_ctr(struct proxy *be)
 {
-	_HA_ATOMIC_INC(&be->be_counters.cum_conn);
+	_HA_ATOMIC_INC(&be->be_counters.cum_sess);
 	HA_ATOMIC_UPDATE_MAX(&be->be_counters.sps_max,
 			     update_freq_ctr(&be->be_sess_per_sec, 1));
 }
diff --git a/include/haproxy/server.h b/include/haproxy/server.h
index 3829bce..787417b 100644
--- a/include/haproxy/server.h
+++ b/include/haproxy/server.h
@@ -174,7 +174,7 @@
 int srv_check_reuse_ws(struct server *srv);
 const struct mux_ops *srv_get_ws_proto(struct server *srv);
 
-/* increase the number of cumulated connections on the designated server */
+/* increase the number of cumulated streams on the designated server */
 static inline void srv_inc_sess_ctr(struct server *s)
 {
 	_HA_ATOMIC_INC(&s->counters.cum_sess);
diff --git a/src/haproxy.c b/src/haproxy.c
index d83a79f..d32d2f5 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -963,19 +963,19 @@
 			chunk_printf(&trash,
 			             "SIGHUP: Proxy %s has no servers. Conn: act(FE+BE): %d+%d, %d pend (%d unass), tot(FE+BE): %lld+%lld.",
 			             p->id,
-			             p->feconn, p->beconn, p->totpend, p->queue.length, p->fe_counters.cum_conn, p->be_counters.cum_conn);
+			             p->feconn, p->beconn, p->totpend, p->queue.length, p->fe_counters.cum_conn, p->be_counters.cum_sess);
 		} else if (p->srv_act == 0) {
 			chunk_printf(&trash,
 			             "SIGHUP: Proxy %s %s ! Conn: act(FE+BE): %d+%d, %d pend (%d unass), tot(FE+BE): %lld+%lld.",
 			             p->id,
 			             (p->srv_bck) ? "is running on backup servers" : "has no server available",
-			             p->feconn, p->beconn, p->totpend, p->queue.length, p->fe_counters.cum_conn, p->be_counters.cum_conn);
+			             p->feconn, p->beconn, p->totpend, p->queue.length, p->fe_counters.cum_conn, p->be_counters.cum_sess);
 		} else {
 			chunk_printf(&trash,
 			             "SIGHUP: Proxy %s has %d active servers and %d backup servers available."
 			             " Conn: act(FE+BE): %d+%d, %d pend (%d unass), tot(FE+BE): %lld+%lld.",
 			             p->id, p->srv_act, p->srv_bck,
-			             p->feconn, p->beconn, p->totpend, p->queue.length, p->fe_counters.cum_conn, p->be_counters.cum_conn);
+			             p->feconn, p->beconn, p->totpend, p->queue.length, p->fe_counters.cum_conn, p->be_counters.cum_sess);
 		}
 		ha_warning("%s\n", trash.area);
 		send_log(p, LOG_NOTICE, "%s\n", trash.area);
diff --git a/src/proxy.c b/src/proxy.c
index eeeb8a9..23170d9 100644
--- a/src/proxy.c
+++ b/src/proxy.c
@@ -2004,11 +2004,11 @@
 	 */
 	if ((p->mode == PR_MODE_TCP || p->mode == PR_MODE_HTTP || p->mode == PR_MODE_SYSLOG) && !(p->cap & PR_CAP_INT))
 		ha_warning("Proxy %s stopped (cumulated conns: FE: %lld, BE: %lld).\n",
-			   p->id, p->fe_counters.cum_conn, p->be_counters.cum_conn);
+			   p->id, p->fe_counters.cum_conn, p->be_counters.cum_sess);
 
 	if ((p->mode == PR_MODE_TCP || p->mode == PR_MODE_HTTP) && !(p->cap & PR_CAP_INT))
 		send_log(p, LOG_WARNING, "Proxy %s stopped (cumulated conns: FE: %lld, BE: %lld).\n",
-			 p->id, p->fe_counters.cum_conn, p->be_counters.cum_conn);
+			 p->id, p->fe_counters.cum_conn, p->be_counters.cum_sess);
 
 	if (p->table && p->table->size && p->table->sync_task)
 		task_wakeup(p->table->sync_task, TASK_WOKEN_MSG);
diff --git a/src/stats.c b/src/stats.c
index 21ec1a0..0682400 100644
--- a/src/stats.c
+++ b/src/stats.c
@@ -2747,7 +2747,7 @@
 				metric = mkf_u32(FO_CONFIG|FN_LIMIT, px->fullconn);
 				break;
 			case ST_F_STOT:
-				metric = mkf_u64(FN_COUNTER, px->be_counters.cum_conn);
+				metric = mkf_u64(FN_COUNTER, px->be_counters.cum_sess);
 				break;
 			case ST_F_BIN:
 				metric = mkf_u64(FN_COUNTER, px->be_counters.bytes_in);