add enhancement proposal for hub in operator

Author: vinamra28

enhancements/hub-in-operator.md

@@ -0,0 +1,132 @@
+---
+status: implementable
+title: Hub in OpenShift Pipelines
+creation-date: "2021-09-07"
+last-updated: "2021-02-27"
+authors: ["vinamra28"]
+---
+
+# Hub in OpenShift Pipelines Operator
+
+<!-- toc -->
+
+- [Summary](#summary)
+- [Motivation](#motivation)
+  - [Goals](#goals)
+  - [Non-Goals](#non-goals)
+- [Requirements](#requirements)
+- [Proposal](#proposal)
+- [Design](#design)
+  - [Handling Upgrades](#handling-upgrades)
+- [Drawbacks](#drawbacks)
+- [Alternatives](#alternatives)
+- [References (optional)](#references-optional)
+<!-- /toc -->
+
+## Summary
+
+Tekton Hub provides a central hub for searching and sharing Tekton resources
+across many distributed Tekton catalogs hosted by various organizations and
+teams. Hub currently displays a curated set of community contributed tasks
+from the Community Catalog. It allows resources to be searched by name or
+its “display name”, filtered by categories (cloud, cli, github etc…), and
+rated by users. This document should cover the way how we can ship Tekton Hub
+in a better way so that users can install their own personalized hub within their
+cluster.
+
+## Motivation
+
+With time Hub is gaining more attention by many users and organizations
+and want to deploy the Hub within their own environment. Keeping this
+in mind we should simply the process of deployment so that with less
+effort hub can be installed on anyone's cluster.
+
+### Goals
+
+Provide a way for users to...
+
+1. Run their own instance of Tekton Hub on their own cluster.
+2. Expose the OpenShift routes so that ODC can use the exposed APIs
+   in `PipelineBuilder`.
+
+### Non-Goals
+
+This TEP will not cover how the user is going to expose the service
+to external world via `Ingress`.
+
+## Requirements
+
+1. Images should be made available to the cluster in case of disconnected install.
+2. Required secrets should be present in the `targetNamespace`.
+
+## Proposal
+
+Have a CRD in Tekton Operator and a controller/reconciler which can handle CRUD operations
+for `Tekton Hub` resources such as API, UI and DB. Whenever a user installs a TektonHub CR
+with required spec it's going to perform following operations:
+
+- Create DB deployment
+- Run DB migration
+- API deployment, service and Route in case of OpenShift
+- UI deployment, service and Route in case of OpenShift
+
+## Design
+
+```yaml
+apiVersion: operator.tekton.dev/v1alpha1
+kind: TektonHub
+metadata:
+  name: hub
+spec:
+  targetNamespace:
+    # <namespace> in which you want to install Tekton Hub. Leave it blank if in case you want to install
+    # in default installation namespace ie `openshift-pipelines` in case of OpenShift and `tekton-pipelines` in case of Kubernetes
+  api:
+    hubConfigUrl: https://raw.githubusercontent.com/tektoncd/hub/main/config.yaml
+```
+
+There would be separate manifests for deploying via Tekton Operator instead of
+having a common `release.yaml`.
+
+### Flow
+
+The installation flow of `Tekton Hub` is as follows:
+
+1. Create the `TektonHub` CR which will create the `targetNamespace` if it's not present.
+1. Create the required secrets for API in the target namespace.
+1. the `Tekton Hub` components in the following order:
+   1. Create `db` secrets
+   1. Create DB deployment, pvc and service
+   1. Run the DB-Migration, if it fails then do not proceed
+   1. After the successful completion of DB-Migration, search for the API secrets
+   1. If API secrets are present then create the remaining components required for API
+   1. Post successful running of API, do the same process for UI
+
+## Handling Upgrades
+
+Whenever there is a new version of OpenShift Pipelines available, all the components
+of Tekton Hub are going to upgrade in the following order:
+
+1. Run the new db-migration
+1. After successful completion of db-migration run the new API and UI server.
+
+## Handling Uninstall
+
+Whenever the CR TektonHub is deleted from the cluster, all the components
+related to Tekton Hub along with `tekton-hub` namespace should be deleted.
+
+## Drawbacks
+
+With current release cycle users may have to wait for the next release of
+OpenShift Pipelines to make it available for OpenShift users.
+
+## Alternatives
+
+### Hub as it's own Operator
+
+We can also create a separate operator for Hub and manage it's lifecycle
+by own instead of relying on OpenShift Pipelines operator.
+
+#### Drawbacks
+
+There will be an overhead to manage one extra operator.