MINOR: backend: add traces for idle connections reuse

Add traces in connect_server() to debug idle connection reuse. These
are attached to stream trace module, as it's already in use in
backend.c with the macro TRACE_SOURCE.

diff --git a/src/backend.c b/src/backend.c
index 0a7875cdf311009536bb347ad4cd7f2ab2ca2eab..4c7aba1f890df7f92bf604aa29794a37dc21b82b 100644 (file)
--- a/src/backend.c
+++ b/src/backend.c
@@ -1325,13 +1325,17 @@ int connect_server(struct stream *s)
        hash = conn_calculate_hash(&hash_params);
 
        /* do not reuse if mode is not http */
-       if (!IS_HTX_STRM(s))
+       if (!IS_HTX_STRM(s)) {
+               DBG_TRACE_STATE("skip idle connections reuse: no htx", STRM_EV_STRM_PROC|STRM_EV_SI_ST, s);
                goto skip_reuse;
+       }
 
        /* first, search for a matching connection in the session's idle conns */
        srv_conn = session_get_conn(s->sess, s->target, hash);
-       if (srv_conn)
+       if (srv_conn) {
+               DBG_TRACE_STATE("reuse connection from session", STRM_EV_STRM_PROC|STRM_EV_SI_ST, s);
                reuse = 1;
+       }
 
        if (srv && !reuse && reuse_mode != PR_O_REUSE_NEVR) {
                /* Below we pick connections from the safe, idle  or
@@ -1354,8 +1358,10 @@ int connect_server(struct stream *s)
                 */
                if (!eb_is_empty(&srv->per_thr[tid].avail_conns)) {
                        srv_conn = srv_lookup_conn(&srv->per_thr[tid].avail_conns, hash);
-                       if (srv_conn)
+                       if (srv_conn) {
+                               DBG_TRACE_STATE("reuse connection from avail", STRM_EV_STRM_PROC|STRM_EV_SI_ST, s);
                                reuse = 1;
+                       }
                }
 
                /* if no available connections found, search for an idle/safe */
@@ -1386,8 +1392,10 @@ int connect_server(struct stream *s)
                                }
                        }
 
-                       if (srv_conn)
+                       if (srv_conn) {
+                               DBG_TRACE_STATE("reuse connection from idle/safe", STRM_EV_STRM_PROC|STRM_EV_SI_ST, s);
                                reuse = 1;
+                       }
                }
        }
 
@@ -1498,6 +1506,7 @@ skip_reuse:
                srv_cs = NULL;
 
                if (srv_conn) {
+                       DBG_TRACE_STATE("alloc new be connection", STRM_EV_STRM_PROC|STRM_EV_SI_ST, s);
                        srv_conn->owner = s->sess;
 
                        /* connection will be attached to the session if