MINOR: checks: improve handling of the servers tracking chain

Server tracking uses the same "tracknext" list for servers tracking
another one and for the servers being tracked. This caused an issue
which was fixed by commit f39c71c ([CRITICAL] fix server state tracking:
it was O(n!) instead of O(n)), consisting in ensuring that a server is
being checked before walking down the list, so that we don't propagate
the up/down information via servers being part of the track chain.

But the root cause is the fact that all servers share the same list.
The correct solution consists in having a list head for the tracked
servers and a list of next tracking servers. This simplifies the
propagation logic, especially for the case where status changes might
be passed to individual servers via the CLI.

diff --git a/include/types/server.h b/include/types/server.h
index 05d47835ecf67aa6dc5199be769036c247584a67..a3775a7c889351a66c213ba9554d70c9d8aa2a23 100644 (file)
--- a/include/types/server.h
+++ b/include/types/server.h
@@ -158,7 +158,9 @@ struct server {
 
        struct conn_src conn_src;               /* connection source settings */
 
-       struct server *tracknext, *track;       /* next server in a tracking list, tracked server */
+       struct server *track;                   /* the server we're currently tracking, if any */
+       struct server *trackers;                /* the list of servers tracking us, if any */
+       struct server *tracknext;               /* next server tracking <track> in <track>'s trackers list */
        char *trackit;                          /* temporary variable to make assignment deferrable */
        int consecutive_errors;                 /* current number of consecutive errors */
        int consecutive_errors_limit;           /* number of consecutive errors that triggers an event */

diff --git a/src/cfgparse.c b/src/cfgparse.c
index 579dbcc530a7d7e915d9ab3ea5b1e81c1cc7013e..aa8bb90cf2d53e9af83b777c5c3eadf908314e91 100644 (file)
--- a/src/cfgparse.c
+++ b/src/cfgparse.c
@@ -7044,8 +7044,8 @@ out_uri_auth_compat:
                                }
 
                                newsrv->track = srv;
-                               newsrv->tracknext = srv->tracknext;
-                               srv->tracknext = newsrv;
+                               newsrv->tracknext = srv->trackers;
+                               srv->trackers = newsrv;
 
                                free(newsrv->trackit);
                                newsrv->trackit = NULL;

diff --git a/src/checks.c b/src/checks.c
index 4af3db726178f54815b7e8d6098a0ec4a218a8fb..069d06d448f2bbc41a1d506cfe04fb1120d694b9 100644 (file)
--- a/src/checks.c
+++ b/src/checks.c
@@ -455,11 +455,10 @@ void set_server_down(struct check *check)
 
                s->counters.down_trans++;
 
-               if (s->state & SRV_CHECKED)
-                       for (srv = s->tracknext; srv; srv = srv->tracknext)
-                               if (!(srv->state & SRV_MAINTAIN))
-                                       /* Only notify tracking servers that are not already in maintenance. */
-                                       set_server_down(&srv->check);
+               for (srv = s->trackers; srv; srv = srv->tracknext)
+                       if (!(srv->state & SRV_MAINTAIN))
+                               /* Only notify tracking servers that are not already in maintenance. */
+                               set_server_down(&srv->check);
        }
 
        check->health = 0; /* failure */
@@ -531,11 +530,10 @@ void set_server_up(struct check *check) {
                Warning("%s.\n", trash.str);
                send_log(s->proxy, LOG_NOTICE, "%s.\n", trash.str);
 
-               if (s->state & SRV_CHECKED)
-                       for (srv = s->tracknext; srv; srv = srv->tracknext)
-                               if (!(srv->state & SRV_MAINTAIN))
-                                       /* Only notify tracking servers if they're not in maintenance. */
-                                       set_server_up(&srv->check);
+               for (srv = s->trackers; srv; srv = srv->tracknext)
+                       if (!(srv->state & SRV_MAINTAIN))
+                               /* Only notify tracking servers if they're not in maintenance. */
+                               set_server_up(&srv->check);
        }
 
        if (check->health >= check->rise)
@@ -576,9 +574,8 @@ static void set_server_disabled(struct check *check) {
        if (!s->proxy->srv_bck && !s->proxy->srv_act)
                set_backend_down(s->proxy);
 
-       if (s->state & SRV_CHECKED)
-               for(srv = s->tracknext; srv; srv = srv->tracknext)
-                       set_server_disabled(&srv->check);
+       for (srv = s->trackers; srv; srv = srv->tracknext)
+               set_server_disabled(&srv->check);
 }
 
 static void set_server_enabled(struct check *check) {
@@ -610,9 +607,8 @@ static void set_server_enabled(struct check *check) {
        Warning("%s.\n", trash.str);
        send_log(s->proxy, LOG_NOTICE, "%s.\n", trash.str);
 
-       if (s->state & SRV_CHECKED)
-               for(srv = s->tracknext; srv; srv = srv->tracknext)
-                       set_server_enabled(&srv->check);
+       for (srv = s->trackers; srv; srv = srv->tracknext)
+               set_server_enabled(&srv->check);
 }
 
 static void check_failed(struct check *check)