<p dir="ltr">Syslog-ng doesn't use an asynchronous dns resolver, but rather it uses the libc one as it wants to keep the ordering of messages.</p>
<p dir="ltr">However it uses an inprocess DNS cache, that should mitigate most dns latency issues as hosts that generate logs should already be in the cache anyway.</p>
<p dir="ltr">If you can't trust that the dns will work, just disable dns resolution eg use-dns(no) or use persist-only dns caching and populate /etc/hosts with those you want to see with names.</p>
<p dir="ltr"><a href="https://www.balabit.com/sites/default/files/documents/syslog-ng-ose-latest-guides/en/syslog-ng-ose-guide-admin/html/example-local-dns.html">https://www.balabit.com/sites/default/files/documents/syslog-ng-ose-latest-guides/en/syslog-ng-ose-guide-admin/html/example-local-dns.html</a></p>
<p dir="ltr">With regards to dns stalling all sources, no its not as long as syslog-ng is running in threaded mode. Only the affected worker is stalled the others will continue.</p>
<div class="gmail_quote">On Aug 22, 2015 5:37 PM, "David Hauck" <<a href="mailto:davidh@netacquire.com">davidh@netacquire.com</a>> wrote:<br type="attribution"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On <a href="mailto:yslog-ng-bounces@lists.balabit.hu">yslog-ng-bounces@lists.balabit.hu</a>] On Behalf Of Scheidler,, <a href="mailto:syslog-ng-bounces@lists.balabit.hu">syslog-ng-bounces@lists.balabit.hu</a> wrote:<br>
> Earlier syslog-ng immediately exited at startup, now it is considering<br>
> dns resolution errors just like connection failures so time-reopen applies.<br>
<br>
OK, thx.<br>
<br>
BTW, I was reading about the DNS resolver blocking the logger (during resolutions, which, in situations where the lookup fails, could result in significant time). What does this mean exactly? Are all destinations/sources blocked during this time?<br>
<br>
> Time-reopen defaults to 60 seconds as I remember as well and I can't remember any patch that would have changed it.<br>
<br>
Thx also - I did locate my configuration setting for this and see that the distribution I'm using resets this default to 10s (so everything's working fine here).<br>
<br>
> On Aug 22, 2015 1:01 AM, "David Hauck" <<a href="mailto:davidh@netacquire.com">davidh@netacquire.com</a>> wrote:<br>
><br>
><br>
> Hi Fabien,<br>
><br>
> On Monday, June 15, 2015 7:08 AM, I wrote: > On Monday, June 15, 2015<br>
> 12:50 AM Fabien Wernli wrote: >> Hi David, >> >> On Fri, Jun 12, 2015<br>
> at 05:09:03PM +0000, David Hauck wrote: >>> Starting syslog-ng: Error<br>
> resolving hostname; >>> host='test.nacc.netacquire.dom' Error<br>
> initializing message pipeline; >>> >>> Unfortunately, this results in<br>
> the entire process failing to start. >> >> This looks a hell lot like<br>
> a resolved issue [1] on github >> >> [1]<br>
> <a href="https://github.com/balabit/syslog-ng/issues/318" rel="noreferrer" target="_blank">https://github.com/balabit/syslog-ng/issues/318</a> > > Yes, indeed! And<br>
> this looks to have been included in v3.6.3 - I'll give this a try.<br>
><br>
> I've finally had a chance to test this and see that it indeed fixes<br>
> outright error. However, I now see the following messages appear every 10s:<br>
><br>
> 20150821 15:54:37.994 err syslog(syslog-ng):Error resolving hostname; host='tester'<br>
> 20150821 15:54:37.994 err syslog(syslog-ng):Initiating connection failed, reconnecting; time_reopen='10'<br>
><br>
> Is there a way to change the timeout? Is this the time-reopen global<br>
> option? Besides DNS lookup retries, what other operations are subject<br>
> to this timeout? Finally, the default (3.7) OSE documentation indicates the time-reopen default is 60s (not 10s like I'm seeing).<br>
><br>
> Thanks,<br>
> -David<br>
><br>
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</blockquote></div>