Icinga's initial threads are linked to core count in host with no way to adjust or limit

[froooooooo]

Currently the number of threads spawned is tied to the number of cores/cpu-threads the host running icinga has. Ideally, we would like to reduce the number of threads icinga needs to just run off of 1
initial thread if possible.

It seems this used to be possible with the init.conf but this was removed a while ago. For example, the value I'm referring to when doing checks is this. The below command shows the threads per icinga.

18-core-host # icinga2 console -e Concurrency
18

4-core-host # icinga2 console -e Concurrency
4

128-core-host-with-2-threads-per-core # icinga2 console -e Concurrency
256

To Reproduce

1. Start icinga and check via icinga2 console -e Concurrency
2. This number correlates directly to the number of cpu-threads which also is 1 icinga process per core/cpu-thread on startup

As shown above, this will change depending on the number of cores the host's cpu has.

Expected behavior

I would prefer a way to minimize this. We are pinning icinga to one core on our hosts, so in theory we should only require 1 thread (based on this logic), however it is still spawning a bunch of threads.

Your Environment

Include as many relevant details about the environment you experienced the problem in

• Version used (icinga2 --version): 2.13.1-1
• Operating System and version: Rhel6/Centos 7
• Enabled features (icinga2 feature list): Enabled features: api checker mainlog

Additional context

I can get any more info if needed. But this is a huge concern for our environment. Thank you!

[leeclemens]

For the sake of cross-referencing: https://community.icinga.com/t/any-way-to-reduce-the-number-of-threads-in-icinga/8840

[Al2Klimov]

Have you tried const Concurrency = 1?

[froooooooo]

Have you tried const Concurrency = 1?

Where should I set this?

[Al2Klimov]

E.g. in the constants.conf.

[froooooooo]

So it looks like this doesn't help. I tried with both const Concurrency = 1 and const concurrency = 1, but both had the same results ie. 1 thread per core.

[Al2Klimov]

Hmm... and -DConcurrency=1 in the systemd file just after icinga2 daemon?

[froooooooo]

No changes as well with this added to systemd.

[Al2Klimov]

Have you done systemctl daemon-reload before restarting Icinga 2?

[julianbrost]

IIRC one of the insights when looking at #9099 was (of course not written down) that there are some places where the number of thread can't be easily controlled by the user at the moment:

icinga2/lib/base/io-engine.cpp

Line 87 in f2563cc

IoEngine::IoEngine() : m_IoContext(), m_KeepAlive(boost::asio::make_work_guard(m_IoContext)), m_Threads(decltype(m_Threads)::size_type(std::thread::hardware_concurrency() * 2u)), m_AlreadyExpiredTimer(m_IoContext)

icinga2/lib/base/threadpool.hpp

Line 39 in f2563cc

ThreadPool(size_t threads = std::thread::hardware_concurrency() * 2u);

[Al2Klimov]

6414ce3

[froooooooo]

Have you done systemctl daemon-reload before restarting Icinga 2?

yes I did and still no luck.

[Al2Klimov]

6414ce3 from #7845 may help.