Milestone step for concurrency in Jenkins - Step-by-Step Execution

Process Flow - Milestone step for concurrency

Start Pipeline

↓

Run Stage 1

↓

Reach Milestone

↓

Check for Previous Milestone

↓

Wait

↓

Run Stage 2

↓

End Pipeline

The pipeline runs stages until it reaches a milestone. If a previous build reached the same milestone, the current build waits or skips to avoid concurrency conflicts.

Execution Sample

Jenkins

pipeline {
  agent any
  stages {
    stage('Build') {
      steps {
        milestone 1
      }
    }
  }
}

This Jenkins pipeline uses a milestone step to prevent concurrent builds from passing the same point simultaneously.

Process Table

Step	Build Number	Milestone Reached	Previous Build Milestone	Action	Pipeline State
1	Build #1	Milestone 1	None	Proceed	Build #1 at Milestone 1
2	Build #2	Milestone 1	Build #1 reached Milestone 1	Wait or Skip	Build #2 waiting at Milestone 1
3	Build #1	Passed Milestone 1	N/A	Continue	Build #1 proceeds past Milestone 1
4	Build #2	Milestone 1	Build #1 passed Milestone 1	Proceed	Build #2 proceeds past Milestone 1
5	Build #2	End	N/A	Complete	Build #2 finished

💡 Build #2 waits at Milestone 1 until Build #1 passes it, then proceeds and finishes.

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
Build #1 State	Not started	At Milestone 1	Passed Milestone 1	Passed Milestone 1	Completed	Completed
Build #2 State	Not started	Waiting at Milestone 1	Waiting at Milestone 1	At Milestone 1	Proceeded	Completed

Key Moments - 2 Insights

Why does Build #2 wait at the milestone instead of proceeding immediately?

Because Build #1 has already reached the same milestone and not passed it yet, Build #2 must wait to avoid concurrency conflicts, as shown in execution_table row 2.

What happens when Build #1 passes the milestone?

Once Build #1 passes the milestone (row 3), Build #2 is allowed to proceed past the milestone (row 4), ensuring only one build passes at a time.

Visual Quiz - 3 Questions

Look at the execution table, what is the state of Build #2 at Step 2?

A Build #2 is proceeding past Milestone 1

B Build #2 has finished

C Build #2 is waiting at Milestone 1

D Build #2 has not started

💡 Hint

Check the 'Action' and 'Pipeline State' columns at Step 2 in the execution_table.

At which step does Build #2 proceed past Milestone 1?

A Step 4

B Step 2

C Step 1

D Step 5

💡 Hint

Look for when Build #1 has passed the milestone and Build #2 moves forward in the execution_table.

If Build #1 never passed Milestone 1, what would happen to Build #2?

A Build #2 would proceed immediately

B Build #2 would wait indefinitely at Milestone 1

C Build #2 would skip the milestone

D Build #2 would fail

💡 Hint

Refer to the waiting behavior shown in execution_table rows 2 and 3.

Concept Snapshot

milestone <number> step in Jenkins pipeline
- Prevents concurrent builds passing the same point
- Later builds wait if earlier builds haven't passed milestone
- Ensures orderly pipeline execution
- Use milestone to avoid race conditions in concurrency

Full Transcript

This visual execution trace shows how the Jenkins milestone step controls concurrency in pipelines. The pipeline starts with Build #1 reaching milestone 1 and proceeding. When Build #2 reaches the same milestone, it detects Build #1 has not passed it yet and waits. After Build #1 passes milestone 1, Build #2 proceeds and finishes. Variables track each build's state at each step. Key moments clarify why builds wait and when they proceed. The quiz tests understanding of build states and milestone behavior. The snapshot summarizes the milestone step's purpose and usage.