Azure Functions Sidecar

A sidecar container for your Azure Functions deployments in Kubernetes.

Introduction

This sidecar application can run next to a Azure Functions deployment in Kubernetes, to provide startup, liveness and readiness information. A function host does not provide this information.

While similar functionality could be implemented using a HttpTrigger, it is quite cumbersome. Similar functionality has not yet been provided by the function host.

Running as a sidecar has the benefit that it is easy to add, and does not interfere with the original function deployment. It can directly access the container, because they both share the same network.

Features

• Provide startup, liveness and readiness endpoints
• Provide metrics endpoint for function metrics

Installation

Modify your deployments to include the additional sidecar container. The sidecar needs to have the master key to access the function host API.

apiVersion: apps/v1
kind: Deployment
spec:
  ..
  template:
    ..
    spec:
      ..
      containers:
        - ... (your function deployment)
        - name: azure-functions-sidecar
          image: (image)
          env:
            - name: Logging__LogLevel__Default
              value: Warning
            - name: Function__Host
              value: http://localhost
            - name: Function__Key
              valueFrom:
                secretKeyRef:
                  name: function-keys-secret
                  key: host.master
          ports:
            - name: http
              containerPort: 5000
          startupProbe:
            httpGet:
              path: /startupz
              port: http
            # ASP.NET first request might be slow, change if needed.
            # timeoutSeconds: 5
          livenessProbe:
            httpGet:
              path: /livez
              port: http
          readinessProbe:
            httpGet:
              path: /readyz
              port: http
          resources:
            limits:
              cpu: 100m
              memory: 128M
            requests:
              cpu: 50m
              memory: 64M

Configure additional probe thresholds if desired. Refer to the Kubernetes documentation for more information.

When any of the probes fail, the whole Pod will be restarted.

Dependenies

This project depends on the azure-functions-host project as a Git submodule, in order to have the API models available (there is no Nuget package). After cloning this repository, ensure to run git submodule update --init --recursive to fetch this dependency as well.

Preparation

Ensure that you have the .NET Core 3.1 SDK installed. Install Docker to build the container.

Compilation

Run dotnet build to build the application. You can run it using dotnet run from the src/Functions.Sidecar folder. Make sure you have a initialized copy of appsettings.json (template included).

License

See the LICENSE.md file (MIT license).