Hi,

I was testing your fix in several environments before replying, unfortunately syslog-ng stills shows a huge RAM consumption in our use of case.

We have two wildcard-file sources defined in our syslog-ng conf file, both of them have the same base-dir reference, but one source has a filename-pattern and the other source has a different one (I think we can't use the same source and several filename-patterns because of the lack of regular expression support). We execute the deletion of obsolete files and folder under base-dir once every 2 days, and we create a lot of new folders and files constantly while using our platform, but the growth of these log files (the ones affected by the filename-pattern) has been pretty low in this test, about 10-20 msgs per second total.

This is some data of the fix test:

Syslog-ng was consuming 21,7G of RAM with 10600 files affected by the filename-pattern and 20000 folders under base-dir (not a single folder were deleted yet so this is the expected behaviour of syslog-ng, and we find it extremely unaffordable)

One hour later, right before the cleaning process was executed, syslog-ng was consuming 35G of RAM, and it didn't decrease after the cleaning, not even a little, with just 380 files affected by the filename-pattern and 2200 folders under base-dir.

There is no message in the syslog-agent queue and all the messages are received by the relay (which ingest messages in an elasticsearch)

For the record, we do noticed a small RAM usage decrease in a previous test in a lab environment when we deleted every folder & file under base-dir (from 870M to 550M).

It seems syslog-ng wildcard-source is not optimized when it has too handle thousands of folders and filename-patterns under base-dir. Have you ever test the wildcard-source with a use of case similar to ours?

Can I send you any more information which may help to find out how to optimize it? I wish I can help with the code but I have no idea of C language :-(

Thanks in advance.

2018-09-04 18:03 GMT+02:00 Nagy, Gábor <gabor.nagy@oneidentity.com>:

Hello,

Thanks for the thorough investigation!

We've checked it and found a memory leak in directory monitoring.

I've pushed the fix to my fork and created a merge request about it:

https://github.com/gaborznagy/syslog-ng/commits/fix-wildcard-memleak

https://github.com/balabit/syslog-ng/pull/2261

Can you verify that this fixes your problem, please?

> log-fifo-size value is 345000, so I assume it can't be a buffer situation since 345000 messages can't occupy 40-50 GB of memory.

Well our default log-msg-size is 64kB so if all messages have a size of log-msg-size then it can be around ~21GB when syslog-ng is buffering.

Best Regards,

Gabor

On Tue, Sep 4, 2018 at 10:50 AM Jose Angel Santiago <jasantiago@stratio.com> wrote:

Hi,

I'm using syslog-ng 3.16.1 with wildcard-file as source (let's call it "syslog-agent), which sends log messages to another syslog-ng acting as a relay.

I've noticed that syslog-agent instances RAM consumption keeps increasing until they leave no free memory in the cluster (each server has 64G of RAM). In my use case, new folders & files are created constantly under base-dir folder, but every 2 days obsolete folders & files are deleted. I assumed that syslog-ng would free some RAM every time those folders & files are deleted, but it doesn't, not even if I run a syslog-ng-ctl reload operation.

log-fifo-size value is 345000, so I assume it can't be a buffer situation since 345000 messages can't occupy 40-50 GB of memory.

I've performed the following test to reproduce the situation in small scale:

- Launch a syslog-agent with a wildcard-file source reading from "/tmp/test/" base-dir. syslog-agent RAM usage is about 125M.

- Run a simple script to create complex folder hierarchy under /tmp/test and some files with 5000 log messages to read from.

- Wait until syslog-agent RAM usage gets 1GB

- Stop script execution and wait until syslog-agent has send all logs to relay.

- Delete everything under /tmp/test and execute syslog-ng-ctl reload operation

- 24 hours after, syslog-agent RAM usage still is 1GB

I've used heaptrack tool as a try to find a memory leak in syslog-ng, you can see in the attached image that iv_list_empty function in iv_list.h file is where most of the RAM usage is.

How do I get syslog-ng to free RAM? Or is it a memory leak?

Thanks in advance.

--

| Jose Angel Santiago

Vía de las dos Castillas, 33, Ática 4, 3ª Planta

28224 Pozuelo de Alarcón, Madrid, Spain

+34 918 286 473 | www.stratio.com

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______________________________________________________________________________
Member info: https://lists.balabit.hu/mailman/listinfo/syslog-ng
Documentation: http://www.balabit.com/support/documentation/?product=syslog-ng
FAQ: http://www.balabit.com/wiki/syslog-ng-faq

--

| Jose Angel Santiago

Vía de las dos Castillas, 33, Ática 4, 3ª Planta

28224 Pozuelo de Alarcón, Madrid, Spain

+34 918 286 473 | www.stratio.com