BUG/MEDIUM: connections: force connections cleanup on server changes

I've been trying to understand a change of behaviour between v2.2dev5 and
v2.2dev6. Indeed our probe is regularly testing to add and remove
servers on a given backend such as:

 # echo "show servers state be_foo" | sudo socat stdio /var/lib/haproxy/stats
 113 be_foo 1 srv0 10.236.139.34 2 0 1 1 263 15 3 4 6 0 0 0 - 31255 -
 113 be_foo 2 srv1 0.0.0.0 0 1 256 256 0 15 3 0 14 0 0 0 - 0 -

 -> curl on the corresponding frontend: reply from server:31255

 # echo "set server be_foo/srv1 addr 10.236.139.34 port 31257" | sudo socat stdio /var/lib/haproxy/stats
 IP changed from '0.0.0.0' to '10.236.139.34', port changed from '0' to '31257' by 'stats socket command'
 # echo "set server be_foo/srv1 weight 256" | sudo socat stdio /var/lib/haproxy/stats
 # echo "set server be_foo/srv1 check-port 8500" | sudo socat stdio /var/lib/haproxy/stats
 health check port updated.
 # echo "set server be_foo/srv1 state ready" | sudo socat stdio /var/lib/haproxy/stats
 # echo "show servers state be_foo" | sudo socat stdio /var/lib/haproxy/stats
 113 be_foo 1 srv0 10.236.139.34 2 0 1 1 105 15 3 4 6 0 0 0 - 31255 -
 113 be_foo 2 srv1 10.236.139.34 2 0 256 256 2319 15 3 2 6 0 0 0 - 31257 -

 -> curl on the corresponding frontend: reply for server:31257
 (notice the difference of weight)

 # echo "set server be_foo/srv1 state maint" | sudo socat stdio /var/lib/haproxy/stats
 # echo "set server be_foo/srv1 addr 0.0.0.0 port 0" | sudo socat stdio /var/lib/haproxy/stats
 IP changed from '10.236.139.34' to '0.0.0.0', port changed from '31257' to '0' by 'stats socket command'
 # echo "show servers state be_foo" | sudo socat stdio /var/lib/haproxy/stats
 113 be_foo 1 srv0 10.236.139.34 2 0 1 1 263 15 3 4 6 0 0 0 - 31255 -
 113 be_foo 2 srv1 0.0.0.0 0 1 256 256 0 15 3 0 14 0 0 0 - 0 -

 -> curl on the corresponding frontend: reply from server:31255

 # echo "set server be_foo/srv1 addr 10.236.139.34 port 31256" | sudo socat stdio /var/lib/haproxy/stats
 IP changed from '0.0.0.0' to '10.236.139.34', port changed from '0' to '31256' by 'stats socket command'
 # echo "set server be_foo/srv1 weight 256" | sudo socat stdio /var/lib/haproxy/stats
 # echo "set server be_foo/srv1 check-port 8500" | sudo socat stdio /var/lib/haproxy/stats
 health check port updated.
 # echo "set server be_foo/srv1 state ready" | sudo socat stdio /var/lib/haproxy/stats
 # echo "show servers state be_foo" | sudo socat stdio /var/lib/haproxy/stats
 113 be_foo 1 srv0 10.236.139.34 2 0 1 1 105 15 3 4 6 0 0 0 - 31255 -
 113 be_foo 2 srv1 10.236.139.34 2 0 256 256 2319 15 3 2 6 0 0 0 - 31256 -

 -> curl on the corresponding frontend: reply from server:31257 (!)

Here we indeed would expect to get an anver from server:31256. The issue
is highly linked to the usage of `pool-purge-delay`, with a value which
is higher than the duration of the test, 10s in our case.

a git bisect between dev5 and dev6 seems to show commit
079cb9af22da6 ("MEDIUM: connections: Revamp the way idle connections are killed")
being the origin of this new behaviour.

So if I understand the later correctly, it seems that it was more a
matter of chance that we did not saw the issue earlier.

My patch proposes to force clean idle connections in the two following
cases:
- we set a (still running) server to maintenance
- we change the ip/port of a server

This commit should be backported to 2.1, 2.0, and 1.9.

Signed-off-by: William Dauchy <w.dauchy@criteo.com>

diff --git a/src/server.c b/src/server.c
index 4d5e706d3a4843c43bf96acabce11b92867001e8..94e7aeed1a8b01ff58eb7cd26bedb3bce051f188 100644 (file)
--- a/src/server.c
+++ b/src/server.c
@@ -55,6 +55,7 @@ static int srv_apply_lastaddr(struct server *srv, int *err_code);
 static int srv_set_fqdn(struct server *srv, const char *fqdn, int dns_locked);
 static void srv_state_parse_line(char *buf, const int version, char **params, char **srv_params);
 static int srv_state_get_version(FILE *f);
+static void srv_cleanup_connections(struct server *srv);
 
 /* List head of all known server keywords */
 static struct srv_kw_list srv_keywords = {
@@ -3669,8 +3670,11 @@ const char *update_server_addr_port(struct server *s, const char *addr, const ch
        }
 
 out:
-       if (changed)
+       if (changed) {
+               /* force connection cleanup on the given server */
+               srv_cleanup_connections(s);
                srv_set_dyncookie(s);
+       }
        if (updater)
                chunk_appendf(msg, " by '%s'", updater);
        chunk_appendf(msg, "\n");
@@ -4832,6 +4836,8 @@ static void srv_update_status(struct server *s)
                        if (s->onmarkeddown & HANA_ONMARKEDDOWN_SHUTDOWNSESSIONS)
                                srv_shutdown_streams(s, SF_ERR_DOWN);
 
+                       /* force connection cleanup on the given server */
+                       srv_cleanup_connections(s);
                        /* we might have streams queued on this server and waiting for
                         * a connection. Those which are redispatchable will be queued
                         * to another server or to the proxy itself.
@@ -5160,6 +5166,37 @@ struct task *srv_cleanup_toremove_connections(struct task *task, void *context,
        return task;
 }
 
+/* cleanup connections for a given server
+ * might be useful when going on forced maintenance or live changing ip/port
+ */
+void srv_cleanup_connections(struct server *srv)
+{
+       struct connection *conn;
+       int did_remove;
+       int i;
+       int j;
+
+       HA_SPIN_LOCK(OTHER_LOCK, &idle_conn_srv_lock);
+       for (i = 0; i < global.nbthread; i++) {
+               did_remove = 0;
+               HA_SPIN_LOCK(OTHER_LOCK, &toremove_lock[i]);
+               for (j = 0; j < srv->curr_idle_conns; j++) {
+                       conn = MT_LIST_POP(&srv->idle_conns[i], struct connection *, list);
+                       if (!conn)
+                               conn = MT_LIST_POP(&srv->safe_conns[i],
+                                                  struct connection *, list);
+                       if (!conn)
+                               break;
+                       did_remove = 1;
+                       MT_LIST_ADDQ(&toremove_connections[i], (struct mt_list *)&conn->list);
+               }
+               HA_SPIN_UNLOCK(OTHER_LOCK, &toremove_lock[i]);
+               if (did_remove)
+                       task_wakeup(idle_conn_cleanup[i], TASK_WOKEN_OTHER);
+       }
+       HA_SPIN_UNLOCK(OTHER_LOCK, &idle_conn_srv_lock);
+}
+
 struct task *srv_cleanup_idle_connections(struct task *task, void *context, unsigned short state)
 {
        struct server *srv;