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Add a TEP with motivation, a few use cases and high level stub proposed solution in proposed state. I also ran the hack/update-toc.sh tool. Signed-off-by: Andrea Frittoli <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,174 @@ | ||
| --- | ||
| status: proposed | ||
| title: Tekton Notifications | ||
| creation-date: '2020-11-18' | ||
| last-updated: '2020-11-18' | ||
| authors: | ||
| - '@afrittoli' | ||
| --- | ||
|
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| # TEP-0032: Tekton Notifications | ||
|
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| <!-- toc --> | ||
| - [Summary](#summary) | ||
| - [Motivation](#motivation) | ||
| - [Goals](#goals) | ||
| - [Non-Goals](#non-goals) | ||
| - [Use Cases (optional)](#use-cases-optional) | ||
| - [Requirements](#requirements) | ||
| - [Proposal](#proposal) | ||
| - [User Experience (optional)](#user-experience-optional) | ||
| - [Alternatives](#alternatives) | ||
| - [References (optional)](#references-optional) | ||
| <!-- /toc --> | ||
|
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| ## Summary | ||
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| This proposal seeks to provide "native notifications" in Tekton Pipelines: | ||
| notifications which are much more easily configurable than the existing | ||
| CloudEvents integration, can fire at important stages of a pipeline and task | ||
| lifecycle, and which allow users greater control over both the filtering of | ||
| resources / events that fire notifications as well as the types of notifications | ||
| that are sent. | ||
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| Tekton users would highly benefit from native notification support in Tekton. | ||
|
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| ## Motivation | ||
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| Tekton is a tool for building CI/CD systems. It allows automating workflows | ||
| using pipelines which may run autonomously most of the times, until something | ||
| goes wrong or they reach as step that require human involvement. | ||
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| Notification can help raising the attention of an human being to a specific | ||
| workflow execution that is need of attention. | ||
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| Several Tekton users ask about notifications in Tekton. We have developed two | ||
| features that may help implementing notifications: | ||
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| - [Cloud events](https://tekton.dev/docs/pipelines/events/#events-via-cloudevents) | ||
| - [Finally](https://tekton.dev/docs/pipelines/pipelines/#adding-finally-to-the-pipeline) | ||
|
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| Cloud events are triggered every time a pipeline or task is started, begins | ||
| executing and is terminated. Cloud events, combined with Tekton Triggers can | ||
| be used to execute tasks and pipelines as a reaction to an event. This is | ||
| used in our dogfooding cluster to generate notifications for failed CD pipelines. | ||
| It works fine, however it requires a good amount of YAML and plumbing resource | ||
| together to achieve the goal of notifications. | ||
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| The "Finally" section in a pipeline allows execution tasks once all regular tasks | ||
| completed execution. Such "final" tasks can be used to send notifications about | ||
| the outcome of a pipeline, as they will always be invoked, even if a task in the | ||
| main pipeline failed. However final tasks are only executed at the end, so they | ||
| cannot be used for "start" notifications, and they are limited to pipelines. | ||
| Work is in progress to allow "final" tasks access to the execution status of tasks | ||
| in the main pipeline. | ||
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| Tekton users would highly benefit from native notification support. | ||
|
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| ### Goals | ||
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| The main goal of the TEP is to design and implement a notification system that | ||
| is both easy to use and flexible, for delivering notification targeted to humans. | ||
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| Notifications are easy to use: enabling and configuring default notifications | ||
| to get something up and running (notifying on every event of every Pipeline/Task) | ||
| requires only few lines of configuration. | ||
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| Notifications are flexible: users are able to configure the precise Pipelines/Tasks | ||
| and events that notifications are sent for. Users can also modify the configuration | ||
| for their chosen notification system. | ||
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| A secondary goal is to make sure that notification can benefit from our growing | ||
| catalog of tasks, several of which have been written to deliver notification through | ||
| different platforms. | ||
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| A third goal is to make notifications easier to troubleshoot and track. | ||
|
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| ### Non-Goals | ||
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| - Build a machine to machine communication protocols | ||
| - Build pre/post execution hook for steps, tasks or pipelines | ||
| - Build a catalog of integration with different notification, chat or email systems | ||
| - Build a system to send large amounts of data produced by a task or pipeline | ||
| - Write a controller for cloud events (even if that could be part of the solution). | ||
| See [tektoncd/pipeline#2944](https://github.com/tektoncd/pipeline/issues/2944) for | ||
| further context. | ||
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| ### Use Cases (optional) | ||
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| - Notify individuals or groups about the failure of a pipeline | ||
| - Notify individuals or groups about the completion of a long running task | ||
| - Notify individuals or groups about the start or a pipeline that was triggered as | ||
| a consequence of an automated event (cron, pull request, manual approval) | ||
|
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| ## Requirements | ||
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| ***This section is a stub and subject to change.*** | ||
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| Once notifications are implemented, we do not want to force Tekton users to modify | ||
| all their existing tasks or pipelines to enable notifications for them: | ||
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| - Allow using catalog tasks as is | ||
| - Allow notifications for pipelines with no change to the pipeline itself | ||
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| For installations that run large number of task and pipelines, the configuration | ||
| of notification should be designed to be scalable and easy to maintain. | ||
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| - Allow selecting pipelines and tasks to be notified about via selectors | ||
| - Allow selecting events to be notified about | ||
| - Allow pipeline and task authors to re-use of notification "rules" | ||
|
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| ## Proposal | ||
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| ***This section is a stub and subject to change.*** | ||
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| The proposal is to introduce notification policies and templates. | ||
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| Notification policies define condition under which we want to trigger a notification; | ||
| they would allow users to: | ||
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| - filter sources such using rules (using CEL?) | ||
| - kind: task, pipeline | ||
| - metadata: name, labels, namespace, annotations(?) | ||
| - filter events such as start, run, success, fail (using CEL or syntax sugar on top) | ||
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| Notification templates define how a notification is sent. They would allow user to: | ||
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| - define the task / pipeline to be executed | ||
| - bind an event type with the inputs to the task / param | ||
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| Both notification policies and templates could be defined a dedicated CRD. | ||
| The policy controller would be responsible to provision `trigger` resources by | ||
| combining the information from the policy and the templates. | ||
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| Which notification template is triggered is decided based on runtime information passed to the `TaskRun` | ||
| or `PipelineRun`, or can be configured on Tekton for each namespace and added to resources | ||
| as an annotation. | ||
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| All resources generated or associated with a notification policy and a notification | ||
| template will be automatically labelled by the notification controller so that they | ||
| can be easily identified and filtered. | ||
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| ### User Experience (optional) | ||
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| Notification targeted to humans is the main goal of this TEP because I would like to make | ||
| sure that requirements for machine targeted notification do not pollute the user experience | ||
| of tekton native notifications. | ||
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| User experience is very important for this proposal. Notification should be easy to use | ||
| and maintain across large number of tasks and pipelines. | ||
|
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| ## Alternatives | ||
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| - Use cloud events + triggers and let user maintain the configuration and plumbing required | ||
| to fit everything together | ||
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| ## References (optional) | ||
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| Additional context for this TEP can be found in the following issues: | ||
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| - [Initial design document](https://docs.google.com/document/d/1ehhGngn2ulnjYX0HUxSyhQGAvcbabSa27UZs3RvZWwU/edit#heading=h.isehsedcrq00) | ||
| - [Actions and Notifications for Tekton](https://github.com/tektoncd/pipeline/issues/1740) | ||
| - [Move cloud events to a separate controller](https://github.com/tektoncd/pipeline/issues/2944) | ||
| - [Events on Tasks and Steps](https://github.com/tektoncd/pipeline/issues/742) | ||
| - [Alternative ways of running triggers](https://github.com/tektoncd/triggers/issues/504) |
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