[syslog-ng] Adding a background thread

Naveen Revanna raveenr at gmail.com
Fri Dec 21 02:06:15 UTC 2018

Hello syslog-ng developers,

I am planning to add a new thread of execution to syslog-ng. I am seeking
inputs/expert advice for the same.

Motivation: I had previously discussed a problem here where syslog-ng would
hang if dns server is unreachable. The reason this was happening was that
getaddrinfo() would take some time to timeout and all syslog-ng tasks would
pile up resulting in delayed execution which would appear that syslog-ng
has hung.

I took the approach of using getaddrinfo_a() which would do the async
resolution of the address. I have recently come to understand that
getaddrinfo_a() finally calls getaddrinfo() in a separate pthread that it
spawns. This is causing some issues resulting in a crash. The stacktrace is
pointing to problem in glib allocators.

Here is what I am thinking. I will call iv_thread() to create a new thread
as part of the main process. All this thread does is execute a fixed task
(which in my case is to just do address resolution).

I am looking for inputs from you developers for pointers as to what would
be a good place to spawn this thread. This thread would do very minimal
stuff and hope not to have much complexity. Are there things that I should
look out for if we have another thread of execution. Do any of you think it
is bad idea and time consuming process to introduce a new thread to
existing syslog-ng.

I have some understanding of the code and have read a bit about ivykis and
some of it's functions. All I'll be bothering you will be for your
expertise and would be doing the development on my side.

Sorry if I am bothering you in your time with family. Happy Holidays :)

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