Process Flow - Master-agent architecture
Master Node
Assign Job
Agent Node
Execute Job
Send Results
Master Node Receives Results
The Jenkins master assigns jobs to agents, which run the jobs and send results back to the master.
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Master-agent architecture in Jenkins - Step-by-Step Execution
Execution Sample
Jenkins
master.launchJob(job1) agent1.execute(job1) agent1.sendResult(master) master.receiveResult(job1)
Master sends a job to agent, agent runs it, then sends back results to master.
Process Table
| Step | Action | Node | Job State | Result Sent | Master State |
|---|---|---|---|---|---|
| 1 | Master assigns job1 | Master | job1 assigned | No | Waiting for result |
| 2 | Agent1 starts job1 | Agent1 | job1 running | No | Waiting for result |
| 3 | Agent1 completes job1 | Agent1 | job1 done | Yes | Waiting for result |
| 4 | Agent1 sends result | Agent1 | job1 done | Yes | Result sent |
| 5 | Master receives result | Master | job1 done | Yes | Result received |
| 6 | Master updates job status | Master | job1 complete | Yes | Job complete |
💡 Job1 completed and result received by master, execution ends.
Status Tracker
| Variable | Start | After Step 1 | After Step 2 | After Step 3 | After Step 5 | Final |
|---|---|---|---|---|---|---|
| job1_state | not assigned | assigned | running | done | done | complete |
| result_sent | No | No | No | Yes | Yes | Yes |
| master_state | idle | waiting for result | waiting for result | waiting for result | result received | job complete |
Key Moments - 3 Insights
Why does the master wait after assigning the job?
Because the master waits for the agent to finish and send back the job result, as shown in steps 1 to 5 in the execution table.
Can the agent run the job without the master assigning it first?
No, the master must assign the job first (step 1) before the agent can start running it (step 2).
What happens if the agent does not send the result back?
The master remains in 'waiting for result' state and does not mark the job complete, as seen in the master_state variable in the tracker.
Visual Quiz - 3 Questions
Test your understanding
Look at the execution table, at which step does the agent start running the job?
💡 Hint
Check the 'Action' and 'Node' columns for when the agent starts the job.
According to the variable tracker, what is the job1_state after step 3?
💡 Hint
Look at the 'job1_state' row under 'After Step 3' in the variable tracker.
If the agent never sends the result, what will the master's state be after step 5?
💡 Hint
Refer to the 'master_state' variable in the tracker and the explanation in key moments.
Concept Snapshot
Jenkins Master-Agent Architecture: - Master assigns jobs to agents. - Agents run jobs and send results back. - Master waits for results before marking jobs complete. - Agents cannot run jobs without master assignment. - Communication ensures distributed job execution.
Full Transcript
In Jenkins master-agent architecture, the master node assigns jobs to agent nodes. The agents execute the assigned jobs and send the results back to the master. The master waits for these results before marking the job as complete. This flow ensures that jobs are distributed and managed efficiently. The master controls job assignment and collects results, while agents handle the execution workload.