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TEP-0077: Partial pipeline execute.
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224 changes: 224 additions & 0 deletions teps/0077-pipeline-partial-execution.md
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---
status: proposed
title: Custom Task SDK
creation-date: '2021-07-21'
last-updated: '2021-07-21'
authors:
- '@jerop'
- '@bobcatfish'
- '@Tomcli'
- '@ScrapCodes'
---

# TEP-0077: Pipeline partial execution

<!-- toc -->
- [Summary](#summary)
- [Motivation](#motivation)
- [Goals](#goals)
- [Non-Goals](#non-goals)
- [Use Cases (optional)](#use-cases-optional)
- [Requirements](#requirements)
- [Proposal](#proposal)
- [Notes/Caveats (optional)](#notescaveats-optional)
- [Risks and Mitigations](#risks-and-mitigations)
- [User Experience (optional)](#user-experience-optional)
- [Performance (optional)](#performance-optional)
- [Design Details](#design-details)
- [Test Plan](#test-plan)
- [Design Evaluation](#design-evaluation)
- [Drawbacks](#drawbacks)
- [Alternatives](#alternatives)
- [Infrastructure Needed (optional)](#infrastructure-needed-optional)
- [Upgrade &amp; Migration Strategy (optional)](#upgrade--migration-strategy-optional)
- [Implementation Pull request(s)](#implementation-pull-request-s)
- [References (optional)](#references-optional)
<!-- /toc -->

## Summary

Add an ability for `PipelineRun` to have disabled tasks i.e. a `PipelineRun`
can execute a `Pipeline` partially.

Allow `PipelineRun` to be created from previous `PipelineRun`.

So, a `PipelineRun` can be partially run or cancelled at run time, and
resumed at a later point with the help of work proposed in this TEP.

Together these will bring in the ability to resume/retry a failed `PipelineRun`

## Motivation

1. A very long Pipeline may fail due to a transient failure, and the user may
want to only rerun the `Tasks` that failed.
2. It is not enough to `retry` a `PipelineTask` n times, as the failures can
be due to e.g. service outage. A manual resume/ retry may be helpful.
3. Iterate quickly, by disabling tasks that take longer time. This can be done
at run time, i.e. without editing pipeline definition.

### Goals

- Partially execute a `Pipeline`, by disabling tasks.
- Resume a failed or cancelled `PipelineRun` from previous `PipelineRun`.
- Discuss how the results/workspaces of disabled tasks can be referenced or
populated from previous `PipelineRun`.

### Non-Goals

- TBD.

### Use Cases (optional)

<!--
Describe the concrete improvement specific groups of users will see if the
Motivations in this doc result in a fix or feature.
Consider both the user's role (are they a Task author? Catalog Task user?
Cluster Admin? etc...) and experience (what workflows or actions are enhanced
if this problem is solved?).
-->

## Requirements

<!--
Describe constraints on the solution that must be met. Examples might include
performance characteristics that must be met, specific edge cases that must
be handled, or user scenarios that will be affected and must be accomodated.
-->

## Proposal

<!--
This is where we get down to the specifics of what the proposal actually is.
This should have enough detail that reviewers can understand exactly what
you're proposing, but should not include things like API designs or
implementation. The "Design Details" section below is for the real
nitty-gritty.
-->

### Notes/Caveats (optional)

<!--
What are the caveats to the proposal?
What are some important details that didn't come across above.
Go in to as much detail as necessary here.
This might be a good place to talk about core concepts and how they relate.
-->

### Risks and Mitigations

<!--
What are the risks of this proposal and how do we mitigate. Think broadly.
For example, consider both security and how this will impact the larger
kubernetes ecosystem.
How will security be reviewed and by whom?
How will UX be reviewed and by whom?
Consider including folks that also work outside the WGs or subproject.
-->

### User Experience (optional)

<!--
Consideration about the user experience. Depending on the area of change,
users may be task and pipeline editors, they may trigger task and pipeline
runs or they may be responsible for monitoring the execution of runs,
via CLI, dashboard or a monitoring system.
Consider including folks that also work on CLI and dashboard.
-->

### Performance (optional)

<!--
Consideration about performance.
What impact does this change have on the start-up time and execution time
of task and pipeline runs? What impact does it have on the resource footprint
of Tekton controllers as well as task and pipeline runs?
Consider which use cases are impacted by this change and what are their
performance requirements.
-->

## Design Details

<!--
This section should contain enough information that the specifics of your
change are understandable. This may include API specs (though not always
required) or even code snippets. If there's any ambiguity about HOW your
proposal will be implemented, this is the place to discuss them.
If it's helpful to include workflow diagrams or any other related images,
add them under "/teps/images/". It's upto the TEP author to choose the name
of the file, but general guidance is to include at least TEP number in the
file name, for example, "/teps/images/NNNN-workflow.jpg".
-->

## Test Plan

<!--
**Note:** *Not required until targeted at a release.*
Consider the following in developing a test plan for this enhancement:
- Will there be e2e and integration tests, in addition to unit tests?
- How will it be tested in isolation vs with other components?
No need to outline all of the test cases, just the general strategy. Anything
that would count as tricky in the implementation and anything particularly
challenging to test should be called out.
All code is expected to have adequate tests (eventually with coverage
expectations).
-->

## Design Evaluation
<!--
How does this proposal affect the reusability, simplicity, flexibility
and conformance of Tekton, as described in [design principles](https://github.com/tektoncd/community/blob/master/design-principles.md)
-->

## Drawbacks

<!--
Why should this TEP _not_ be implemented?
-->

## Alternatives

<!--
What other approaches did you consider and why did you rule them out? These do
not need to be as detailed as the proposal, but should include enough
information to express the idea and why it was not acceptable.
-->

## Infrastructure Needed (optional)

<!--
Use this section if you need things from the project/SIG. Examples include a
new subproject, repos requested, github details. Listing these here allows a
SIG to get the process for these resources started right away.
-->

## Upgrade & Migration Strategy (optional)

<!--
Use this section to detail wether this feature needs an upgrade or
migration strategy. This is especially useful when we modify a
behavior or add a feature that may replace and deprecate a current one.
-->

## Implementation Pull request(s)

<!--
Once the TEP is ready to be marked as implemented, list down all the Github
Pull-request(s) merged.
Note: This section is exclusively for merged pull requests, for this TEP.
It will be a quick reference for those looking for implementation of this TEP.
-->

## References (optional)

1. [Google Doc: Disabling a Task in a Pipeline](https://docs.google.com/document/d/1rleshixafJy4n1CwFlfbAJuZjBL1PQSm3b0Q9s1B_T8/edit#heading=h.jz9jia3av6h1)
2. [TEP-0065-rejected](https://github.com/tektoncd/community/pull/422)
1 change: 1 addition & 0 deletions teps/README.md
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Expand Up @@ -218,3 +218,4 @@ This is the complete list of Tekton teps:
|[TEP-0070](0070-tekton-catalog-task-platform-support.md) | Platform support in Tekton catalog | proposed | 2021-06-02 |
|[TEP-0071](0071-custom-task-sdk.md) | Custom Task SDK | proposed | 2021-06-15 |
|[TEP-0072](0072-results-json-serialized-records.md) | Results: JSON Serialized Records | proposed | 2021-05-11 |
|[TEP-0077](0077-pipeline-partial-execution.md) | Pipeline partial execution | proposed | 2021-07-21 |

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