Clarification on Jenkins Job Distribution Mechanism

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We are running a Jenkins instance with 9 agents, all of which have identical configurations and resource availability (CPU, memory, etc.). However, we’ve observed that the job distribution seems to be uneven, with only two agents consistently receiving more load while the others remain relatively idle.

Could you provide clarification on how the Jenkins controller allocates jobs to agents? Specifically:

  1. How does Jenkins determine which agent to assign a job to when multiple agents are available?
  2. Does Jenkins use a round-robin or load-balancing approach, or is there another factor that influences this behavior?
  3. Are there any settings or plugins we can use to better distribute jobs evenly across all agents?

Any guidance or recommendations would be appreciated.

Thank you!!

2

It depends, for freestyle jobs I think Jenkins by default will try to use the same agent as for the previous build. Don’t know how this is for pipeline jobs as they can use multiple agents.
There are plugins that allow to change the behaviour of the loadbalancer, e.g. Scoring Load Balancer