Matrix

Overview
Configuring a Matrix
Fan Out
- PipelineTasks with Tasks
- PipelineTasks with Custom Tasks
Retries

Overview

Matrix is used to fan out Tasks in a Pipeline. This doc will explain the details of matrix support in Tekton.

Documentation for specifying Matrix in a Pipeline:

🌱 Matrix is an alpha feature. The enable-api-fields feature flag must be set to "alpha" to specify Matrix in a PipelineTask. The embedded-status feature flag must be set to "minimal" to specify Matrix in a PipelineTask.

Configuring a Matrix

A Matrix supports the following features:

Concurrency Control
Parameters
Context Variables
Results

Concurrency Control

The default maximum count of TaskRuns or Runs from a given Matrix is 256. To customize the maximum count of TaskRuns or Runs generated from a given Matrix, configure the default-max-matrix-combinations-count in config defaults. When a Matrix in PipelineTask would generate more than the maximum TaskRuns or Runs, the Pipeline validation would fail.

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apiVersion: v1
kind: ConfigMap
metadata:
  name: config-defaults
data:
  default-service-account: "tekton"
  default-timeout-minutes: "20"
  default-max-matrix-combinations-count: "1024"
  ...

For more information, see installation customizations.

Parameters

The Matrix will take Parameters of type "array" only, which will be supplied to the PipelineTask by substituting Parameters of type "string" in the underlying Task. The names of the Parameters in the Matrix must match the names of the Parameters in the underlying Task that they will be substituting.

In the example below, the test Task takes browser and platform Parameters of type "string". A Pipeline used to fan out the Task using Matrix would have two Parameters of type "array", and it would execute nine TaskRuns:

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apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: platform-browser-tests
spec:
  params:
    - name: platforms
      type: array
      default:
        - linux
        - mac
        - windows
    - name: browsers
      type: array
      default:
        - chrome
        - safari
        - firefox    
  tasks:
  - name: fetch-repository
    taskRef:
      name: git-clone
    ...
  - name: test
    matrix:
      params:
        - name: platform
          value: $(params.platforms)
        - name: browser
          value: $(params.browsers)
    taskRef:
      name: browser-test
  ...

A Parameter can be passed to either the matrix or params field, not both.

For further details on specifying Parameters in the Pipeline and passing them to PipelineTasks, see documentation.

Specifying both `params` and `matrix` in a `PipelineTask`

In the example below, the test Task takes browser and platform Parameters of type "string". A Pipeline used to run the Task on three browsers (using matrix) and one platform (using params) would be specified as such and execute three TaskRuns:

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apiVersion: tekton.dev/v1beta1
kind: Pipeline
metadata:
  name: platform-browser-tests
spec:
  tasks:
  - name: fetch-repository
    taskRef:
      name: git-clone
    ...
  - name: test
    matrix:
      params:
        - name: browser
          value:
            - chrome
            - safari
            - firefox
    params:
      - name: platform
        value: linux
    taskRef:
      name: browser-test
  ...

Context Variables

Similarly to the Parameters in the Params field, the Parameters in the Matrix field will accept context variables that will be substituted, including:

PipelineRun name, namespace and uid
Pipeline name
PipelineTask retries

Results

Specifying Results in a Matrix

Consuming Results from previous TaskRuns or Runs in a Matrix, which would dynamically generate TaskRuns or Runs from the fanned out PipelineTask, is supported. Producing Results in from a PipelineTask with a Matrix is not yet supported - see further details.

Matrix supports Results of type String that are passed in individually:

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tasks:
...
- name: task-4
  taskRef:
    name: task-4
  matrix:
  - name: values
    value: 
    - (tasks.task-1.results.foo) # string
    - (tasks.task-2.results.bar) # string
    - (tasks.task-3.results.rad) # string

For further information, see the example in PipelineRun with Matrix and Results.

When we support Results of type Array at the Pipeline level, we will support passing Results into the Matrix.

Note: Results of type Array are not yet supported in the Pipeline level.

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tasks:
...
- name: task-5
  taskRef:
    name: task-5
  matrix:
  - name: values
    value: (tasks.task-4.results.foo) # array

Results from fanned out PipelineTasks

Consuming Results from fanned out PipelineTasks will not be in the supported in the initial iteration of Matrix. Supporting consuming Results from fanned out PipelineTasks will be revisited after array and object Results are supported.

Fan Out

`PipelineTasks` with `Tasks`

When a PipelineTask has a Task and a Matrix, the Task will be executed in parallel TaskRuns with substitutions from combinations of Parameters.

In the example below, nine TaskRuns are created with combinations of platforms (“linux”, “mac”, “windows”) and browsers (“chrome”, “safari”, “firefox”).

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apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: platform-browsers
  annotations:
    description: |
            A task that does something cool with platforms and browsers
spec:
  params:
    - name: platform
    - name: browser
  steps:
    - name: echo
      image: alpine
      script: |
                echo "$(params.platform) and $(params.browser)"
---
# run platform-browsers task with:
#   platforms: linux, mac, windows
#   browsers: chrome, safari, firefox
apiVersion: tekton.dev/v1beta1
kind: PipelineRun
metadata:
  generateName: matrixed-pr-
spec:
  serviceAccountName: 'default'
  pipelineSpec:
    tasks:
      - name: platforms-and-browsers
        matrix:
          params:
            - name: platform
              value:
                - linux
                - mac
                - windows
            - name: browser
              value:
                - chrome
                - safari
                - firefox
        taskRef:
          name: platform-browsers

When the above PipelineRun is executed, these are the TaskRuns that are created:

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$ tkn taskruns list

NAME                                         STARTED        DURATION     STATUS
matrixed-pr-6lvzk-platforms-and-browsers-8   11 seconds ago   7 seconds    Succeeded
matrixed-pr-6lvzk-platforms-and-browsers-6   12 seconds ago   7 seconds    Succeeded
matrixed-pr-6lvzk-platforms-and-browsers-7   12 seconds ago   9 seconds    Succeeded
matrixed-pr-6lvzk-platforms-and-browsers-4   12 seconds ago   7 seconds    Succeeded
matrixed-pr-6lvzk-platforms-and-browsers-5   12 seconds ago   6 seconds    Succeeded
matrixed-pr-6lvzk-platforms-and-browsers-3   13 seconds ago   7 seconds    Succeeded
matrixed-pr-6lvzk-platforms-and-browsers-1   13 seconds ago   8 seconds    Succeeded
matrixed-pr-6lvzk-platforms-and-browsers-2   13 seconds ago   8 seconds    Succeeded
matrixed-pr-6lvzk-platforms-and-browsers-0   13 seconds ago   8 seconds    Succeeded

When the above Pipeline is executed, its status is populated with ChildReferences of the above TaskRuns. The PipelineRun status tracks the status of all the fanned out TaskRuns. This is the PipelineRun after completing successfully:

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apiVersion: tekton.dev/v1beta1
kind: PipelineRun
metadata:
  generateName: matrixed-pr-
  labels:
    tekton.dev/pipeline: matrixed-pr-6lvzk
  name: matrixed-pr-6lvzk
  namespace: default
spec:
  pipelineSpec:
    tasks:
    - matrix:
        params:
          - name: platform
            value:
              - linux
              - mac
              - windows
          - name: browser
              value:
                - chrome
                - safari
                - firefox
      name: platforms-and-browsers
      taskRef:
        kind: Task
        name: platform-browsers
  serviceAccountName: default
  timeout: 1h0m0s
status:
  pipelineSpec:
    tasks:
      - matrix:
          params:
            - name: platform
              value:
                - linux
                - mac
                - windows
            - name: browser
              value:
                - chrome
                - safari
                - firefox
        name: platforms-and-browsers
        taskRef:
          kind: Task
          name: platform-browsers
  startTime: "2022-06-23T23:01:11Z"
  completionTime: "2022-06-23T23:01:20Z"
  conditions:
    - lastTransitionTime: "2022-06-23T23:01:20Z"
      message: 'Tasks Completed: 1 (Failed: 0, Cancelled 0), Skipped: 0'
      reason: Succeeded
      status: "True"
      type: Succeeded
  childReferences:
  - apiVersion: tekton.dev/v1beta1
    kind: TaskRun
    name: matrixed-pr-6lvzk-platforms-and-browsers-4
    pipelineTaskName: platforms-and-browsers
  - apiVersion: tekton.dev/v1beta1
    kind: TaskRun
    name: matrixed-pr-6lvzk-platforms-and-browsers-6
    pipelineTaskName: platforms-and-browsers
  - apiVersion: tekton.dev/v1beta1
    kind: TaskRun
    name: matrixed-pr-6lvzk-platforms-and-browsers-2
    pipelineTaskName: platforms-and-browsers
  - apiVersion: tekton.dev/v1beta1
    kind: TaskRun
    name: matrixed-pr-6lvzk-platforms-and-browsers-1
    pipelineTaskName: platforms-and-browsers
  - apiVersion: tekton.dev/v1beta1
    kind: TaskRun
    name: matrixed-pr-6lvzk-platforms-and-browsers-7
    pipelineTaskName: platforms-and-browsers
  - apiVersion: tekton.dev/v1beta1
    kind: TaskRun
    name: matrixed-pr-6lvzk-platforms-and-browsers-0
    pipelineTaskName: platforms-and-browsers
  - apiVersion: tekton.dev/v1beta1
    kind: TaskRun
    name: matrixed-pr-6lvzk-platforms-and-browsers-8
    pipelineTaskName: platforms-and-browsers
  - apiVersion: tekton.dev/v1beta1
    kind: TaskRun
    name: matrixed-pr-6lvzk-platforms-and-browsers-3
    pipelineTaskName: platforms-and-browsers
  - apiVersion: tekton.dev/v1beta1
    kind: TaskRun
    name: matrixed-pr-6lvzk-platforms-and-browsers-5
    pipelineTaskName: platforms-and-browsers

To execute this example yourself, run PipelineRun with Matrix.

`PipelineTasks` with `Custom Tasks`

When a PipelineTask has a Custom Task and a Matrix, the Custom Task will be executed in parallel Runs with substitutions from combinations of Parameters.

In the example below, eight Runs are created with combinations of CEL expressions, using the CEL Custom Task.

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apiVersion: tekton.dev/v1beta1
kind: PipelineRun
metadata:
  generateName: matrixed-pr-
spec:
  serviceAccountName: 'default'
  pipelineSpec:
    tasks:
      - name: platforms-and-browsers
        matrix:
          params:
            - name: type
              value:
                - "type(1)"
                - "type(1.0)"
            - name: colors
              value:
                - "{'blue': '0x000080', 'red': '0xFF0000'}['blue']"
                - "{'blue': '0x000080', 'red': '0xFF0000'}['red']"
            - name: bool
              value:
                - "type(1) == int"
                - "{'blue': '0x000080', 'red': '0xFF0000'}['red'] == '0xFF0000'"
        taskRef:
          apiVersion: cel.tekton.dev/v1alpha1
          kind: CEL

When the above PipelineRun is executed, these Runs are created:

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$ k get run.tekton.dev

NAME                                         SUCCEEDED   REASON              STARTTIME   COMPLETIONTIME
matrixed-pr-4djw9-platforms-and-browsers-0   True        EvaluationSuccess   10s         10s
matrixed-pr-4djw9-platforms-and-browsers-1   True        EvaluationSuccess   10s         10s
matrixed-pr-4djw9-platforms-and-browsers-2   True        EvaluationSuccess   10s         10s
matrixed-pr-4djw9-platforms-and-browsers-3   True        EvaluationSuccess   9s          9s
matrixed-pr-4djw9-platforms-and-browsers-4   True        EvaluationSuccess   9s          9s
matrixed-pr-4djw9-platforms-and-browsers-5   True        EvaluationSuccess   9s          9s
matrixed-pr-4djw9-platforms-and-browsers-6   True        EvaluationSuccess   9s          9s
matrixed-pr-4djw9-platforms-and-browsers-7   True        EvaluationSuccess   9s          9s

When the above PipelineRun is executed, its status is populated with ChildReferences of the above Runs. The PipelineRun status tracks the status of all the fanned out Runs. This is the PipelineRun after completing:

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apiVersion: tekton.dev/v1beta1
kind: PipelineRun
metadata:
  generateName: matrixed-pr-
  labels:
    tekton.dev/pipeline: matrixed-pr-4djw9
  name: matrixed-pr-4djw9
  namespace: default
spec:
  pipelineSpec:
    tasks:
      - matrix:
          params:
            - name: type
              value:
                - type(1)
                - type(1.0)
            - name: colors
              value:
                - '{''blue'': ''0x000080'', ''red'': ''0xFF0000''}[''blue'']'
                - '{''blue'': ''0x000080'', ''red'': ''0xFF0000''}[''red'']'
            - name: bool
              value:
                - type(1) == int
                - '{''blue'': ''0x000080'', ''red'': ''0xFF0000''}[''red''] == ''0xFF0000'''
        name: platforms-and-browsers
        taskRef:
          apiVersion: cel.tekton.dev/v1alpha1
          kind: CEL
  serviceAccountName: default
  timeout: 1h0m0s
status:
  pipelineSpec:
    tasks:
      - matrix:
          params:
            - name: type
              value:
                - type(1)
                - type(1.0)
            - name: colors
              value:
                - '{''blue'': ''0x000080'', ''red'': ''0xFF0000''}[''blue'']'
                - '{''blue'': ''0x000080'', ''red'': ''0xFF0000''}[''red'']'
            - name: bool
              value:
                - type(1) == int
                - '{''blue'': ''0x000080'', ''red'': ''0xFF0000''}[''red''] == ''0xFF0000'''
        name: platforms-and-browsers
        taskRef:
          apiVersion: cel.tekton.dev/v1alpha1
          kind: CEL  
  startTime: "2022-06-28T20:49:40Z"
  completionTime: "2022-06-28T20:49:41Z"
  conditions:
    - lastTransitionTime: "2022-06-28T20:49:41Z"
      message: 'Tasks Completed: 1 (Failed: 0, Cancelled 0), Skipped: 0'
      reason: Succeeded
      status: "True"
      type: Succeeded  
  childReferences:
    - apiVersion: tekton.dev/v1alpha1
      kind: Run
      name: matrixed-pr-4djw9-platforms-and-browsers-1
      pipelineTaskName: platforms-and-browsers
    - apiVersion: tekton.dev/v1alpha1
      kind: Run
      name: matrixed-pr-4djw9-platforms-and-browsers-2
      pipelineTaskName: platforms-and-browsers
    - apiVersion: tekton.dev/v1alpha1
      kind: Run
      name: matrixed-pr-4djw9-platforms-and-browsers-3
      pipelineTaskName: platforms-and-browsers
    - apiVersion: tekton.dev/v1alpha1
      kind: Run
      name: matrixed-pr-4djw9-platforms-and-browsers-4
      pipelineTaskName: platforms-and-browsers
    - apiVersion: tekton.dev/v1alpha1
      kind: Run
      name: matrixed-pr-4djw9-platforms-and-browsers-5
      pipelineTaskName: platforms-and-browsers
    - apiVersion: tekton.dev/v1alpha1
      kind: Run
      name: matrixed-pr-4djw9-platforms-and-browsers-6
      pipelineTaskName: platforms-and-browsers
    - apiVersion: tekton.dev/v1alpha1
      kind: Run
      name: matrixed-pr-4djw9-platforms-and-browsers-7
      pipelineTaskName: platforms-and-browsers
    - apiVersion: tekton.dev/v1alpha1
      kind: Run
      name: matrixed-pr-4djw9-platforms-and-browsers-0
      pipelineTaskName: platforms-and-browsers

Retries

The retries field is used to specify the number of times a PipelineTask should be retried when its TaskRun or Run fails, see the documentation for further details. When a PipelineTask is fanned out using Matrix, a given TaskRun or Run executed will be retried as much as the field in the retries field of the PipelineTask.

For example, the PipelineTask in this PipelineRun will be fanned out into three TaskRuns each of which will be retried once:

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apiVersion: tekton.dev/v1beta1
kind: PipelineRun
metadata:
  generateName: matrixed-pr-with-retries-
spec:
  pipelineSpec:
    tasks:
      - name: matrix-and-params
        matrix:
          params:
            - name: platform
              value:
                - linux
                - mac
                - windows
        params:
          - name: browser
            value: chrome
        retries: 1
        taskSpec:
          params:
            - name: platform
            - name: browser
          steps:
            - name: echo
              image: alpine
              script: |
                echo "$(params.platform) and $(params.browser)"
                exit 1

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