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[BUG] global.tune.maxaccept must be limited even in mono-process mode

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On overloaded systems, it sometimes happens that hundreds or thousands
of incoming connections are queued in the system's backlog, and all get
dequeued at once. The problem is that when haproxy processes them and
does not apply any limit, this can take some time and the internal date
does not progress, resulting in wrong timer measures for all sessions.

The most common effect of this is that all of these sessions report a
large request time (around several hundreds of ms) which is in fact
caused by the time spent accepting other connections. This might happen
on shared systems when the machine swaps.

For this reason, we finally apply a reasonable limit even in mono-process
mode. Accepting 100 connections at once is fast enough for extreme cases
and will not cause that much of a trouble when the system is saturated.
This commit is contained in:
Willy Tarreau 2009-03-01 08:35:41 +01:00
parent 368480cf45
commit f49d1df25c
2 changed files with 4 additions and 4 deletions
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4
doc/configuration.txt
View File

@ -251,10 +251,10 @@ tune.maxaccept <number>
Sets the maximum number of consecutive accepts that a process may perform on
a single wake up. High values give higher priority to high connection rates,
while lower values give higher priority to already established connections.
This value is unlimited by default in single process mode. However, in
This value is limited to 100 by default in single process mode. However, in
multi-process mode (nbproc > 1), it defaults to 8 so that when one process
wakes up, it does not take all incoming connections for itself and leaves a
part of them to other processes. Setting this value to zero or less disables
part of them to other processes. Setting this value to -1 completely disables
the limitation. It should normally not be needed to tweak this value.
tune.maxpollevents <number>

4
src/haproxy.c
View File

@ -585,11 +585,11 @@ void init(int argc, char **argv)
if (global.tune.maxpollevents <= 0)
global.tune.maxpollevents = MAX_POLL_EVENTS;
if (global.tune.maxaccept <= 0) {
if (global.tune.maxaccept == 0) {
if (global.nbproc > 1)
global.tune.maxaccept = 8; /* leave some conns to other processes */
else
global.tune.maxaccept = -1; /* accept all incoming conns */
global.tune.maxaccept = 100; /* accept many incoming conns at once */
}
if (arg_mode & (MODE_DEBUG | MODE_FOREGROUND)) {