Add a TEP to start measuring Pipelines performance

This PR starts a TEP to begin to measure tekton pipelines performance
and address tektoncd/pipeline#540

This first iteration just tries to describe the problem vs suggesting
the solution.

It DOES recommend measuring SLOs and SLIs as a goal, which is kind of
part of the solution, so if we think it's useful we could step back even
further, but I think this is a reasonable path forward, curious what
other folks think!

teps/0036-start-measuring-tekton-pipelines-performance.md

@@ -0,0 +1,99 @@
+---
+status: proposed
+title: Start Measuring Tekton Pipelines Performance
+creation-date: '2020-11-20'
+last-updated: '2020-11-20'
+authors:
+- '@bobcatfish'
+---
+
+# TEP-0036: Start Measuring Tekton Pipelines Performance
+
+<!-- toc -->
+- [Summary](#summary)
+- [Motivation](#motivation)
+  - [Goals](#goals)
+  - [Non-Goals](#non-goals)
+  - [Use Cases (optional)](#use-cases-optional)
+- [Requirements](#requirements)
+- [References (optional)](#references-optional)
+<!-- /toc -->
+
+## Summary
+
+Up until this point, we have left it to our users to report back to us on how well Tekton Pipelines performs. Relying on
+our users in this way means that we can’t easily inform users about what performance to expect and also means that we
+usually only catch and fix performance issues after releases.
+
+This proposal is all about finding an incremental step forward we can take towards being more proactive in responding to
+performance issues, and will also enable us to be able to evaluate the performance impact of implementation decisions
+going forward.
+
+Issue: [tektoncd/pipeline#540](https://github.com/tektoncd/pipeline/issues/540)
+
+## Motivation
+
+* To be able to understand and communicate about Tekton performance on an ongoing basis
+* Be able to answer questions like:
+  * How much overhead does a Task add?
+  * How much overhead does a Pipeline add?
+  * How much overhead does using a Tekton Bundle vs referencing a Task in my cluster add?
+  * If we switch out X component for Y component in the controller implementation, how does this impact performance?
+  * How much better or worse does release X perform than release Y?
+  * What characteristics should I look for when choosing what kind of machine to tun the Tekton Pipelines controller on?
+ * Being able to get ahead of issues such as [tektoncd/pipeline#3521](https://github.com/tektoncd/pipeline/issues/3521)
+
+### Goals
+
+The goal of this proposal is to avoid trying to boil the performance and loadtesting ocean all at once, and to instead
+identify some (relatively) small step we can take towards starting to gather this kind of information, so we can build
+from there.
+
+* Identify Service Level Indicators for Tekton Pipelines (as few as possible to start with, maybe just one)
+* For each Service Level Indicator define a target range (SLO) for some known setup
+* Setup infrastructure required such that:
+  * Contributors and users can find the data they need on Tekton Performance
+  * Performance is measured regularly at some interval (e.g. daily, weekly, per release)
+  * Reliable and actionable alerting is setup (if feasible) to notify maintainers when SLOs are violated
+
+Reference: [Definitions of SLIs and SLOs](https://landing.google.com/sre/sre-book/chapters/service-level-objectives/).
+These are worded in terms of running observable services. Since Tekton Pipelines is providing a service that can be run
+by others (vs hosting a "Tekton Pipelines" instance we expect users to use) our situation is a bit different, but I
+think the same SLI and SLO concepts can be applied.
+
+### Non-Goals
+
+These are all goals we likely want to tackle in subsequent TEPs so the groundwork we lay here shouldn’t preclude any of
+these:
+* [Benchmarking](https://dave.cheney.net/2013/06/30/how-to-write-benchmarks-in-go)
+* Load testing (unless we define our initial SLOs to include it?), i.e. how does the system perform under X load
+* Stress testing, i.e. where are the limits of the system’s performance
+* Soak testing, i.e. continuous load over a long period of time
+* Chaos testing, i.e. how does the system perform in the presence of errors
+* Other Tekton projects (e.g. Triggers, CLI, Dashboard, etc.)
+
+### Use Cases (optional)
+
+* As a user of Tekton Pipelines (possibly named @skaegi) supporting users creating Pipelines with 50+ tasks with many
+  uses of params and results ([tektoncd/pipeline#3251](https://github.com/tektoncd/pipeline/issues/3521)) I can
+  confidently upgrade without worrying about a performance degradation
+* As any user for Tekton Pipelines, I can upgrade without being afraid of performance regressions
+* As a maintainer of Tekton Pipelines, I can swap out one library for another in the controller code (e.g. different
+  serialization library or upgrade to knative/pkg) and understand how this impacts performance
+* As a maintainer of Tekton Pipelines, I do not have to be nervous that our users will be exposed to serious performance
+  regressions
+* As a possible user evaluating Tekton Pipelines, I can understand what performance to expect and choose the machines to
+  run it on accordingly
+
+## Requirements
+
+* Start with a bare minimum set of SLIs/SLOs and iterate from there
+* Access to the new infrastructure should be given to all “build cops”
+* All members of the community should be able to view metrics via public dashboards
+* Metrics should be aggregated carefully with a preference toward distributions and percentiles vs averages (see
+[the Aggregation section in this chapter on SLOs](https://landing.google.com/sre/sre-book/chapters/service-level-objectives/))
+
+## References (optional)
+
+* Original Issue: [tektoncd/pipeline#540](https://github.com/tektoncd/pipeline/issues/540)
+* Recent performance issue: ([tektoncd/pipeline#3251](https://github.com/tektoncd/pipeline/issues/3521))

teps/README.md

@@ -144,3 +144,4 @@ This is the complete list of Tekton teps:
 |[TEP-0029](0029-step-workspaces.md) | step-and-sidecar-workspaces | proposed | 2020-10-02 |
 |[TEP-0030](0030-workspace-paths.md) | workspace-paths | proposed | 2020-10-18 |
 |[TEP-0031](0031-tekton-bundles-cli.md) | tekton-bundles-cli | proposed | 2020-11-18 |
+|[TEP-0036](0036-start-measuring-tekton-pipelines-performance.md) | Start Measuring Tekton Pipelines Performance | proposed | 2020-11-20 |