Container-Native Architecture

Tim Gross | Product Manager, Joyent | @0x74696d

Container-native?

Containers are a first class citizen.

Each container is an equal peer on the network.

Remember: your mission is not "manage VMs."

Your mission is what your application does for your organization.

Infrastructure (undifferentiated heavy lifting) is incidental cost and incidental complexity.

Application containers make the full promise of cloud computing possible...

but require new ways of working.

Let me tell you a story...

Our problem at DF:

"Works on my machine"

Slow, non-atomic deploys

Dependency isolation

Version 1: AMIs

Bake a server image for each application for each deploy.

Deploy by standing up entirely new stack.

The Good:

Immutable infrastructure!

Blue/green deploys!

DevOps kool-aid for everyone!

The Bad and/or Ugly:

Deployments are soooo slow!

One VM per service instance -> poor utilization

Add more microservices? Add more AMIs, VMs, and ELBs!

OMGWTFBBQFML... deployments are soooo slow!

Version 2: Docker

Human-and-machine-readable build documentation.

No more "works on my machine."

Fix dependency isolation.

Interface-based approach to application deployment.

Deployments are fast! Yay!

Ok, what's wrong?

Can we avoid NAT?

Can we avoid NAT?

Single Point of Failure

DNS

Simple discovery! But...

Can't address individual hosts behind a record.

No health checking.

TTL caching.

Health checks

Naive health checking == cascading failures

Utilization

One container per VM!

More complexity!

Separate lifecycle for VMs and app containers

Containers don't have their own IP

Pass through proxy for all outbound requests

All packets go through NAT or port forwarding

We can do better!

The Container-Native Alternative?

Remove the middleman!

Applications ask for discovery of upstream services.

Applications tell the discovery service where to find them.

Applications report if they are healthy.

The Container-Native Alternative

Push responsibility of the application topology away from the network infrastructure and into the application itself where it belongs.

Responsibilities of a Container

Registration

Self-introspection

Heartbeats

Look for change

Respond to change

No sidecars

Application-Aware Health Checks

No packaging tooling into another service

App container lifecycle separate from discovery service

Respond quickly to changes

Demo

Legacy Pre-Container Apps

• Registration: wrap start of app in a shell script
• Self-introspection: self-test?
• Heartbeats: um...
• Look for change: ???
• Respond to change: profit?

#!/bin/bash
# startup script for our awesomeapp

# register with consul
curl --fail -s -X PUT -d @myservice.json \
      http://consul.example.com:8500/v1/agent/service/register

# start health check daemon and background it
/opt/check-health-of-awesomeapp.sh &

# run app
/opt/awesomeapp serve --bind 0.0.0.0 -p 8080
  

Containerbuddy to the rescue!

Containerbuddy:

A shim to help make existing apps container-native

• Registration: registers to Consul on startup
• Self-introspection: execute external health check
• Heartbeats: send TTL heathcheck to Consul
• Look for change: poll Consul for changes
• Respond to change: execute external response behavior

No Supervision

Containerbuddy is PID1

Returns exit code of shimmed process back to Docker Engine (or Triton) and dies

Attaches stdout/stderr from app to stdout/stderr of container

Demo App

$ cat ./app/Dockerfile

# a minimal Node.js container including containerbuddy
FROM node:slim

# install curl
RUN apt-get update && \
    apt-get install -y \
    curl && \
    rm -rf /var/lib/apt/lists/*

# install a simple http server
RUN npm install -g json http-server

# add containerbuddy and all our configuration
ADD opt/containerbuddy /opt/containerbuddy/
  

$ cat ./nginx/Dockerfile

# a minimal Nginx container including containerbuddy and a
# simple virtulhost config
FROM nginx:latest

# install curl and unzip
RUN apt-get update && apt-get install -y \
    curl \
    unzip && \
    rm -rf /var/lib/apt/lists/*

# install consul-template
RUN curl -Lo /tmp/consul_template_0.11.0_linux_amd64.zip \
    https://github.com/hashicorp/consul-template/releases/download\
    /v0.11.0/consul_template_0.11.0_linux_amd64.zip && \
unzip -d /bin /tmp/consul_template_0.11.0_linux_amd64.zip

# add containerbuddy and all our configuration
ADD opt/containerbuddy /opt/containerbuddy/
ADD etc/nginx/conf.d /etc/nginx/conf.d/
  

$ cat ./nginx/opt/containerbuddy/reload-nginx.sh

# fetch latest virtualhost template from Consul k/v
curl -s --fail consul:8500/v1/kv/nginx/template?raw \
    > /tmp/virtualhost.ctmpl

# render virtualhost template using values from Consul and reload Nginx
consul-template \
  -once \
  -consul consul:8500 \
  -template \
  "/tmp/virtualhost.ctmpl:/etc/nginx/conf.d/default.conf:nginx -s reload"
  

nginx:
  image: 0x74696d/containerbuddy-demo-nginx
  mem_limit: 512m
  ports:
  - 80
  links:
  - consul:consul
  restart: always
  environment:
  - CONTAINERBUDDY=file:///opt/containerbuddy/nginx.json
  command: >
    /opt/containerbuddy/containerbuddy
    nginx -g "daemon off;"
  

{
  "consul": "consul:8500",
  "services": [
    {
      "name": "nginx",
      "port": 80,
      "health": "/usr/bin/curl --fail -s http://localhost/health",
      "poll": 10,
      "ttl": 25
    }
  ],
  "backends": [
    {
      "name": "app",
      "poll": 7,
      "onChange": "/opt/containerbuddy/reload-nginx.sh"
    }
  ]
}
  

echo 'Starting Consul.'
docker-compose -p example up -d consul

# get network info from consul. alternately we can push this into
# a DNS A-record to bootstrap the cluster
CONSUL_IP=$(docker inspect example_consul_1 \
            | json -a NetworkSettings.IPAddress)

echo "Writing template values to Consul at ${CONSUL_IP}"
curl --fail -s -X PUT --data-binary @./nginx/default.ctmpl \
      http://${CONSUL_IP}:8500/v1/kv/nginx/template

echo 'Opening consul console'
open http://${CONSUL_IP}:8500/ui
  

Starting application servers and Nginx
example_consul_1 is up-to-date
Creating example_nginx_1...
Creating example_app_1...
Waiting for Nginx at 72.2.115.34:80 to pick up initial configuration.
...................
Opening web page... the page will reload every 5 seconds with any updates.
Try scaling up the app!
docker-compose -p example scale app=3
    

echo 'Starting application servers and Nginx'
docker-compose -p example up -d

# get network info from Nginx and poll it for liveness
NGINX_IP=$(docker inspect example_nginx_1 \
           | json -a NetworkSettings.IPAddress)
echo "Waiting for Nginx at ${NGINX_IP} to pick up initial configuration."
while :
  do
  sleep 1
  curl -s --fail -o /dev/null "http://${NGINX_IP}/app/" && break
  echo -ne .
done
echo
echo 'Opening web page... the page will reload every 5 seconds'
echo 'with any updates.'
open http://${NGINX_IP}/app/
  

Does it blend scale?

$ docker-compose -p example scale app=3
Creating and starting 2... done
Creating and starting 3... done
  

Demo App