Multi-Container Pods

Sometimes, two services need to work together, like:
- A web server
- A logging agent
You want them work as a pair and be independent of each other
For these kinds of tasks, Multi-container pods are created and they can share same networks as well as same volumes
There are three common patterns for using multiple containers in a pod:
- Sidecar
- Adapter
- Ambassador

How to create

In the pod YAML, under spec, the containers field is an array.
This allows you to define multiple containers in a single pod

    spec:
      containers:
        - name: web-server
          image: web-server-image
        - name: logger
          image: logger-image

One container runs a web server
Another container named logger handles logging

Patterns

Sidecar Pattern

A helper container runs alongside the main one which we saw above.
Example: a logger that collects logs from the web server

Adapter Pattern

It is used to transform or modify data before it’s sent out.
Example: adapter container converts logs to a common format before sending to the logger

Ambassador Pattern

Works like a proxy for network requests.
Example: Your app connects to different databases so instead of changing the app code, the ambassador container reroutes requests to the right database

Note:

Regardless of which pattern you choose, the definition remains the same.

⬅️ Node Affinity | Init Containers ➡️