On 08/10/2012 01:46 AM, Andrew Beekhof wrote:
> As someone that uses libqb to log a metric buttload to files and
> syslogs on a regular basis... I have to ask "why?".
>
> Even prior to libqb, I've never seen anything that would suggest a
> process was blocked waiting for syslog or a file (and thats with 5 or
> more processes logging to the same place).
> Syslog will just start dropping messages if you log too much, so I'm
> inclined to say you're solving a theoretical problem :)
>
> Something to think about.
>
In the past, the syslog API would block because it sent messages over
IPC without O_NONBLOCK applied to the file descriptor. When syslog
daemon got backed up, the syslog API would block, triggering totem timeouts.
At one point, syslog was blocking approximately 1 second per message
(this was a bug that was fixed).
It was not a theoretical problem in the past. I am not sure about now
adays - probably depends on how glibc implements syslog presently vs 6
yeaers ago when threaded logging was introduced. If it still uses a
blocking fd, then it is needed.
At one time I had implemented a non-blocking (IE: O_NONBLOCK) syslog api
function but that has been removed.
Regards
-steve
> On Fri, Aug 10, 2012 at 1:27 AM, Jan Friesse <jfriesse@xxxxxxxxxx> wrote:
>> Syslog and file log can block, so it's good idea to use libqb threaded
>> mode to prevent it.
>>
>> Signed-off-by: Jan Friesse <jfriesse@xxxxxxxxxx>
>> ---
>> exec/logsys.c | 2 ++
>> 1 files changed, 2 insertions(+), 0 deletions(-)
>>
>> diff --git a/exec/logsys.c b/exec/logsys.c
>> index 6ed5c4f..ed16bc7 100644
>> --- a/exec/logsys.c
>> +++ b/exec/logsys.c
>> @@ -230,6 +230,7 @@ static int logsys_config_file_set_unlocked (
>> qb_log_ctl(logsys_loggers[subsysid].target_id,
>> QB_LOG_CONF_ENABLED,
>> (logsys_loggers[subsysid].mode & LOGSYS_MODE_OUTPUT_FILE));
>> + qb_log_ctl(logsys_loggers[subsysid].target_id, QB_LOG_CONF_THREADED, QB_TRUE);
>>
>> return (0);
>> }
>> @@ -355,6 +356,7 @@ int _logsys_system_setup(
>> } else {
>> qb_log_ctl(QB_LOG_SYSLOG, QB_LOG_CONF_ENABLED, QB_FALSE);
>> }
>> + qb_log_ctl(QB_LOG_SYSLOG, QB_LOG_CONF_THREADED, QB_TRUE);
>> qb_log_ctl(QB_LOG_SYSLOG, QB_LOG_CONF_PRIORITY_BUMP, LOG_INFO - LOG_DEBUG);
>>
>> qb_log_filter_ctl(QB_LOG_BLACKBOX, QB_LOG_FILTER_ADD,
>> --
>> 1.7.1
>>
>> _______________________________________________
>> discuss mailing list
>> discuss@xxxxxxxxxxxx
>> http://lists.corosync.org/mailman/listinfo/discuss
> _______________________________________________
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