Hi,
We are running Jenkins with about 20 build agents on separate VMs (with up to 4 executors each). The master has 4 CPUs, so I would expect a load of about 4 when there's "a lot of work" to be done.
However, no job is ever scheduled on the master itself, and still we can observe very high load levels on the master when many jobs are running concurrently on the agents. For example, one of our test suites launches about 30 jobs (lasting 5-20min each) in a 1h time slot and at that moment the master reaches a load of up to 40, with all CPUs fully occupied! However, looking at the UI, all jobs clearly run on the agents, and the master simply shows as 'Idle'.
When I look at Jenkins' own monitoring, I see a huge amount of Computer.threadPoolForRemoting and similar threads with a summary stating Threads on master: Number = 415, Maximum = 511, Total started = 7,731,717.
Can anyone give some insight on what could be going on? What can be the reasons for high load on the master when all the jobs are running on agents?
Regards,
Dominik