OK, I got the first one figured out myself ...

  flush-limit( 1000 )

does not work.

  flush-limit( "1000" )

does, which is inconsistent with the usual syslog-ng.conf behaviour. And setting it to "1" actually fixed the slow propagation to ES for me.

Now I need to see whether the crash still occurs.

Another question that came up: Is it possible to do flushing based on a time interval and not on a message count in the queue? It's rather unsatisfactory to wait for critical messages to appear in ES.

Best regards,

  Peter.

> On 24 Nov 2016, at 12:28, Peter Eckel <lists@eckel-edv.de> wrote:
>
> I'm currently investigating the Syslog NG -> Elasticsearch 2 destination for a project I'm working on, and started using basically the sample configuration in Peter Czanik's blog article. Thanks, by the way, for the great tutorial.
>
> There is one thing I'm currently struggling with: On my test system I have a fairly low volume of messages, and there seems to be an issue with flushing the cache of Syslog NG to Elasticsearch. To be precise: It doesn't happen. I can easily force a cache flush by reloading Syslog NG, but if I just keep it sitting there it doesn't log anything at all to Elasticsearch (while logs to files, e.g. /var/log/messages, are happening in real time).
>
> I tried configuring the flush-limit() in the elasticsearch2 destination, but the configuration prevents syslog-ng from starting with an error message:
>
>> Nov 23 17:30:28 rpm-test syslog-ng[14527]: Error parsing destination, destination plugin flush-limit not found in /etc/syslog-ng/conf.d/elasticsearch.conf at line 9, column 5:
>> Nov 23 17:30:28 rpm-test syslog-ng[14527]: included from /etc/syslog-ng/syslog-ng.conf line 68, column 1
>> Nov 23 17:30:28 rpm-test syslog-ng[14527]: flush-limit( 1000 )
>> Nov 23 17:30:28 rpm-test syslog-ng[14527]: ^^^^^^^^^^^
>> Nov 23 17:30:28 rpm-test syslog-ng[14527]: syslog-ng documentation: http://www.balabit.com/support/documentation/?product=syslog-ng
>> Nov 23 17:30:28 rpm-test syslog-ng[14527]: mailing list: https://lists.balabit.hu/mailman/listinfo/syslog-ng
>
> If I remove the flush-limit() line, the config loads without a problem.

[fixed]

>
> After some hours of operation, Syslog NG actually crashed on reload with a memory corruption issue (might be unlelated):
>
>> Nov 23 17:50:14 rpm-test
>> systemd[1]: Started System Logger Daemon.
>> Nov 24 11:04:11 rpm-test systemd[1]: Reloaded System Logger Daemon.
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: *** Error in `/usr/sbin/syslog-ng': malloc(): memory corruption (fast): 0x00000000023293df ***
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: ======= Backtrace: =========
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libc.so.6(+0x7b184)[0x7f87e29b7184]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libc.so.6(+0x7e877)[0x7f87e29ba877]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libc.so.6(__libc_calloc+0xb4)[0x7f87e29bc2d4]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libglib-2.0.so.0(g_malloc0+0x17)[0x7f87e39e32c7]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(log_multiplexer_new+0x13)[0x7f87e4529833]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(cfg_tree_new_mpx+0x12)[0x7f87e4521872]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(+0x30136)[0x7f87e4522136]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(+0x2fc11)[0x7f87e4521c11]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(+0x2fb2b)[0x7f87e4521b2b]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(+0x2fc11)[0x7f87e4521c11]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(+0x302a9)[0x7f87e45222a9]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(+0x2fc11)[0x7f87e4521c11]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(cfg_tree_compile_rule+0x35)[0x7f87e4522375]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(cfg_tree_compile+0x4b)[0x7f87e45224cb]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(cfg_tree_start+0x16)[0x7f87e4522576]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(cfg_init+0x16e)[0x7f87e451d58e]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(+0x400de)[0x7f87e45320de]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(+0x407d7)[0x7f87e45327d7]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libivykis.so.0(+0x3b4f)[0x7f87e2f1cb4f]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libivykis.so.0(+0x5193)[0x7f87e2f1e193]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libivykis.so.0(+0x5810)[0x7f87e2f1e810]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libivykis.so.0(iv_main+0x44)[0x7f87e2f1f7d4]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libsyslog-ng-3.8.so.0(main_loop_run+0x74)[0x7f87e4532734]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /usr/sbin/syslog-ng(main+0x1b8)[0x4017b8]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /lib64/libc.so.6(__libc_start_main+0xf5)[0x7f87e295db15]
>> Nov 24 11:04:15 rpm-test syslog-ng[31599]: /usr/sbin/syslog-ng[0x4018dd]

[status unknown]

>
> OS Version is CentOS 7.2, Syslog NG 5.8.1 (installed from Peter's repository), Elasticsearch 5.0.1 (installed from Elastic's repo). The machine is a freshly installed system.

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