BUG/MINOR: limits: compute_ideal_maxconn: don't cap remain if fd_hard_limit=0

'global.fd_hard_limit' stays uninitialized, if haproxy is started with -m
(global.rlimit_memmax). 'remain' is the MAX between soft and hard process fd
limits. It will be always bigger than 'global.fd_hard_limit' (0) in this case.

So, if we reassign 'remain' to the 'global.fd_hard_limit' unconditionally,
calculated then 'maxconn' will be even negative and the DEFAULT_MAXCONN (100)
will be set as the 'ideal_maxconn'.

During the 'global.maxconn' calculations in set_global_maxconn(), if the
provided 'global.rlimit_memmax' is quite big, system will refuse to calculate
based on its 'global.maxconn' and we will do a fallback to the 'ideal_maxconn',
which is 100.

Same problem for the configs with SSL frontends and backends.

This fixes the issue #2899.

This should be backported to v3.1.0.

(cherry picked from commit 060f441199aa97d9735dd553bafd231ca615f723)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit 95197ec04e241f33803909c9c6182e832b6ed16e)
[cf: Applied on src/haproxy.c]
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>

diff --git a/src/haproxy.c b/src/haproxy.c
index 142a1f8..5b79414 100644 (file)
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -1463,8 +1463,14 @@ static int compute_ideal_maxconn()
            && !global.rlimit_memmax)
                global.fd_hard_limit = DEFAULT_MAXFD;
 
-       if (remain > global.fd_hard_limit)
+       if (global.fd_hard_limit && (remain > global.fd_hard_limit)) {
+               /* cap remain only when global.fd_hard_limit > 0, i.e.: either
+                * there were no any other limits set and it's defined by lines
+                * above as DEFAULT_MAXFD (100), or fd_hard_limit is explicitly
+                * provided in config.
+                */
                remain = global.fd_hard_limit;
+       }
 
        /* subtract listeners and checks */
        remain -= global.maxsock;