The Helm Sidecar

This repo implements the Sidecar pattern for containers using Helm in a minimalist fashion.

Setup

Run the following commands to set up a local Kubernetes and install the pattern using Helm (the package manager for Kubernetes).

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
brew bundle
kind create cluster
helm install --wait sidecar .

(Note that this worfklow assume macOS, although there is support for Brew on Linux ;)

Manually Testing the Pattern

To manually interact with sidecar containers inside the Kubernetes pods created by Helm, we can do the following:

FIRST_POD=$(kubectl get pods | grep Running | cut -d' ' -f1 | head -n1)
kubectl exec -it $FIRST_POD --container=ubuntu -- bash

Now we are inside the Ubuntu container we are going to use as a "client" for both Redis and Memcached.

Let's install Netcat to do some low-level connectivity testing:

apt update && apt install --yes netcat

Let's verify that neither Redis nor Memcached are running in this container:

ps -ef

Now we can send a "ping" to the Redis sidecare over local networking in the Pod:

echo -e '*1\r\n$4\r\nPING\r\n' \
  | nc -q 0 localhost 6379

+PONG

...and a stats command to the Memcached sidecar:

echo -e 'stats' \
  | nc -q 0 localhost 11211

STAT pid 1
STAT uptime 1685
STAT time 1613674569

... truncated output ...

STAT moves_within_lru 0
STAT direct_reclaims 0
STAT lru_bumps_dropped 0
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