From 81362c98eb4c8e9ff6d02408015a502e31c17d98 Mon Sep 17 00:00:00 2001 From: Yann Ylavic Date: Tue, 25 Apr 2017 22:53:11 +0000 Subject: [PATCH] Follow up to r1789220. Document the implicit behaviour of ListenCoresBucketsRatio when multiple Listen-ers are configured on the same IP:port. git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1792675 13f79535-47bb-0310-9956-ffa450edef68 --- docs/manual/mod/mpm_common.xml | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/docs/manual/mod/mpm_common.xml b/docs/manual/mod/mpm_common.xml index 43067511477..2978b20794e 100644 --- a/docs/manual/mod/mpm_common.xml +++ b/docs/manual/mod/mpm_common.xml @@ -300,6 +300,27 @@ in *BSDs. MaxSpareThreads lower bound values. The number of children processes needs to be a multiple of the number of buckets to optimally accept connections.

+ + + Multiple <directive>Listen</directive>ers or Apache HTTP servers on + the same IP address and port +

Setting the SO_REUSEPORT option on the listening socket(s) + consequently allows multiple processes (sharing the same EUID, + e.g. root) to bind to the the same IP address and port, + without the binding error raised by the system in the usual case.

+

This also means that multiple instances of Apache httpd configured on a + same IP:port and with a positive ListenCoresBucketsRatio + would start without an error too, and then run with incoming connections + evenly distributed accross both instances (this is NOT a recommendation or + a sensible usage in any case, but just a notice that it would prevent such + possible issues to be detected).

+

Within the same instance, Apache httpd will check and fail to start if + multiple Listen directives on the exact same IP (or + hostname) and port are configured, thus avoiding the creation of some + duplicated buckets which would be useless and kill performances. However + it can't (and won't try harder to) catch all the possible overlapping cases + (like a hostname resolving to an IP used elsewhere).

+ -- 2.47.3