Replicate webhook pods for resiliency

config/webhook-hpa.yaml

@@ -0,0 +1,65 @@
+# Copyright 2020 The Tekton Authors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+apiVersion: autoscaling/v2beta1
+kind: HorizontalPodAutoscaler
+metadata:
+  name: tekton-pipelines-webhook
+  namespace: tekton-pipelines
+  labels:
+    app.kubernetes.io/name: webhook
+    app.kubernetes.io/component: webhook
+    app.kubernetes.io/instance: default
+    app.kubernetes.io/version: "devel"
+    app.kubernetes.io/part-of: tekton-pipelines
+    # tekton.dev/release value replaced with inputs.params.versionTag in pipeline/tekton/publish.yaml
+    pipeline.tekton.dev/release: "devel"
+    # labels below are related to istio and should not be used for resource lookup
+    version: "devel"
+spec:
+  minReplicas: 1
+  maxReplicas: 5
+  scaleTargetRef:
+    apiVersion: apps/v1
+    kind: Deployment
+    name: tekton-pipelines-webhook
+  metrics:
+    - type: Resource
+      resource:
+        name: cpu
+        targetAverageUtilization: 100
+---
+apiVersion: policy/v1beta1
+kind: PodDisruptionBudget
+metadata:
+  name: tekton-pipelines-webhook
+  namespace: tekton-pipelines
+  labels:
+    app.kubernetes.io/name: webhook
+    app.kubernetes.io/component: webhook
+    app.kubernetes.io/instance: default
+    app.kubernetes.io/version: "devel"
+    app.kubernetes.io/part-of: tekton-pipelines
+    # tekton.dev/release value replaced with inputs.params.versionTag in pipeline/tekton/publish.yaml
+    pipeline.tekton.dev/release: "devel"
+    # labels below are related to istio and should not be used for resource lookup
+    version: "devel"
+spec:
+  minAvailable: 80%
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: webhook
+      app.kubernetes.io/component: webhook
+      app.kubernetes.io/instance: default
+      app.kubernetes.io/part-of: tekton-pipelines

config/webhook.yaml

@@ -1,4 +1,4 @@
-# Copyright 2019 The Tekton Authors
+# Copyright 2020 The Tekton Authors
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -54,12 +54,32 @@ spec:
         app: tekton-pipelines-webhook
         version: "devel"
     spec:
+      affinity:
+        podAntiAffinity:
+          preferredDuringSchedulingIgnoredDuringExecution:
+          - podAffinityTerm:
+              labelSelector:
+                matchLabels:
+                  app.kubernetes.io/name: webhook
+                  app.kubernetes.io/component: webhook
+                  app.kubernetes.io/instance: default
+                  app.kubernetes.io/part-of: tekton-pipelines
+              topologyKey: kubernetes.io/hostname
+            weight: 100
       serviceAccountName: tekton-pipelines-webhook
       containers:
       - name: webhook
         # This is the Go import path for the binary that is containerized
         # and substituted here.
         image: ko://github.com/tektoncd/pipeline/cmd/webhook
+        # Resource request required for autoscaler to take any action for a metric
+        resources:
+          requests:
+            cpu: 100m
+            memory: 100Mi
+          limits:
+            cpu: 500m
+            memory: 500Mi
         env:
         - name: SYSTEM_NAMESPACE
           valueFrom:

docs/install.md

@@ -19,6 +19,8 @@ This guide explains how to install Tekton Pipelines. It covers the following top
    will create a cluster running locally, with RBAC enabled and your user granted
    the `cluster-admin` role.
 
+1. If you want to support high availability usecases, install a [Metrics Server](https://github.com/kubernetes-sigs/metrics-server) on your cluster. 
+
 1. Choose the version of Tekton Pipelines you want to install. You have the following options:
 
    * **[Official](https://github.com/tektoncd/pipeline/releases)** - install this unless you have
@@ -349,6 +351,12 @@ data:
 
 You can create a custom release of Tekton Pipelines by following and customizing the steps in [Creating an official release](https://github.com/tektoncd/pipeline/blob/master/tekton/README.md#create-an-official-release). For example, you might want to customize the container images built and used by Tekton Pipelines.
 
+## Configuring High Availability
+
+If you want to run Tekton Pipelines in a way so that webhooks are resiliant against failures and support high concurrency scenarios, you need to run a [Metrics Server](https://github.com/kubernetes-sigs/metrics-server) in your Kubernetes cluster. This is required by the [Horizontal Pod Autoscalers](https://kubernetes.io/docs/tasks/run-application/horizontal-pod-autoscale/) to compute the replica count. 
+
+**Note:** The default configuration is defined in [webhook-hpa.yaml](./../config/webhook-hpa.yaml) which could be customized to better fit a  specific usecase.
+
 ## Next steps
 
 To get started with Tekton Pipelines, see the [Tekton Pipelines Tutorial](./tutorial.md) and take a look at our [examples](https://github.com/tektoncd/pipeline/tree/master/examples).