GitLab CI basics - Step-by-Step Execution

Process Flow - GitLab CI basics

Push code to GitLab repo

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GitLab detects push event

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GitLab CI reads .gitlab-ci.yml

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Pipeline starts: jobs run in stages

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Jobs execute scripts on runners

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Jobs report success or failure

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Pipeline finishes with overall status

This flow shows how pushing code triggers GitLab CI to run jobs defined in the .gitlab-ci.yml file, executing them step-by-step and reporting results.

Execution Sample

Git

stages:
  - build
  - test

build_job:
  stage: build
  script:
    - echo "Building..."
test_job:
  stage: test
  script:
    - echo "Testing..."

This simple GitLab CI config defines two stages: build and test, each with one job that prints a message.

Process Table

Step	Action	Job	Stage	Script Run	Job Status	Pipeline Status
1	Push code to repo	-	-	-	-	pending
2	GitLab detects push	-	-	-	-	pending
3	Start pipeline	-	-	-	-	running
4	Run build_job	build_job	build	echo "Building..."	success	running
5	Run test_job	test_job	test	echo "Testing..."	success	success

💡 All jobs completed successfully, pipeline status is success.

Status Tracker

Variable	Start	After Step 4	After Step 5	Final
Pipeline Status	pending	running	success	success
build_job Status	not started	success	success	success
test_job Status	not started	not started	success	success

Key Moments - 3 Insights

Why does the pipeline status change from 'pending' to 'running' before jobs start?

The pipeline status changes to 'running' as soon as GitLab starts executing jobs (see step 3 in execution_table). This means the pipeline is active even if no job has finished yet.

What happens if a job fails? Does the pipeline continue?

If a job fails, the pipeline status becomes 'failed' and subsequent jobs in later stages do not run. This is shown by the job status and pipeline status columns in the execution_table.

Why do jobs run in the order of stages?

Jobs run stage by stage to ensure dependencies. In the example, 'build' stage runs before 'test' stage (see 'Stage' column in execution_table). This order is defined in the 'stages' list in the config.

Visual Quiz - 3 Questions

Look at the execution table, what is the pipeline status after step 4?

A success

B running

C pending

D failed

💡 Hint

Check the 'Pipeline Status' column at step 4 in the execution_table.

At which step does the 'test_job' start running?

A Step 5

B Step 4

C Step 3

D Step 2

💡 Hint

Look at the 'Job' and 'Step' columns in the execution_table to find when 'test_job' runs.

If the 'build_job' fails, what will happen to the pipeline status?

A It will remain 'pending'

B It will become 'success'

C It will become 'failed'

D It will skip to 'test' stage

💡 Hint

Refer to the key_moments explanation about job failure impact on pipeline status.

Concept Snapshot

GitLab CI basics:
- Push code triggers pipeline
- .gitlab-ci.yml defines stages and jobs
- Jobs run in stage order
- Each job runs scripts on runners
- Pipeline status reflects job results
- Failure stops later jobs

Full Transcript

GitLab CI basics start when you push code to a GitLab repository. GitLab detects this push and reads the .gitlab-ci.yml file to know what jobs to run. The pipeline starts and jobs run in the order of stages defined. Each job executes its script on a runner and reports success or failure. The pipeline status updates accordingly and finishes when all jobs complete or a failure occurs. This visual trace shows the pipeline moving from pending to running, then success after all jobs finish.