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thoughtarray / haproxy-consul-template

Run a HAProxy container that is configured by Consul Template
MIT License
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haproxy-consul-template

The purpose of this is to serve as the TH of the CRTH (Consul, Registrator, Consul [T]emplate, [H]AProxy) stack for service discovery.

About

Disclaimer

This project is not production ready and is not tested throughly...yet.

Architecture

This image uses S6 (specifically s6-overlay) as its supervisor. I recommend using this image on a per-machine level (such as a ECS instance in an ECS cluster) as apposed to a per-app level (like a side-kick process).

How to use

Required (probably) settings

The main two settings to customize is the Consul location environment variables CONSUL_ADDR and CONSUL_PORT, and the Consul Template template for HAProxy /usr/local/etc/consul-template/templates/haproxy.ctmpl.

Optional settings

Another component that you may be interested in customizing is the Consul Template config file which lives here: /usr/local/etc/consul-template/consul-template.conf.

Example

docker run --name service-proxy -p 80:80 -p 443:443 \
  -e "CONSUL_ADDR=<ip/host of Consul>" \
  -e "CONSUL_PORT=8500" \
  -v "/path/on/host:/usr/local/etc/consul-template/templates/haproxy.ctmpl:ro" \
  haproxy-consul-template

# Optionally:
# -v "/path/on/host:/usr/local/etc/consul-template/consul-template.conf:ro"

Harder decisions

The hardest decision is how your HAProxy template is to be written and now the data is to be designed in Consul's key-value store. I've written a sample in this project's ./example directory. You can run the curl commands on a test Consul instance to populate the test data. You can use the haproxy.example.ctmpl file in your docker run ... command to test what the config would look like.

To view the product, you can do something like this:

# You are on the host
docker exec -ti haproxy-consul-template ash

# You are now in the container
less /usr/local/etc/haproxy/haproxy.cfg

# If the OS complains at you and less doesn't work, do this and try again:
export TERM=xterm

Testing reload performance

cd /path/to/this/repo

# Start test Consul instance
docker run -d --name consul -p 8500:8500 \
  progrium/consul -server -bootstrap -ui-dir /ui
# ^ UI accessible at http://localhost:8500/ui/

# Build KV tree on test Consul
./example/populate_consul.sh "<ip/host of Consul>"

# Start test app
docker run --name test-app -d -p 5000:5000 alpine sh \
  -c "(echo 'Hello, world' > /tmp/index.html) && httpd -v -f -p 5000 -h /tmp/"

# Start service proxy
docker run -d --name service-proxy -p 80:80 -p 1936:1936 \
  -e "CONSUL_ADDR=<ip/host of Consul>" \
  -v "$(pwd)/example/haproxy.example.ctmpl:/usr/local/etc/consul-template/templates/haproxy.ctmpl:ro" \
  haproxy-consul-template

# Get baseline performance
ab -c 10 -n 10000 -H "X-IDS-ENV: dev" "http://127.0.0.1/test/"

# Now for the tricky part.  You'll want to run the `ab` program again.  After
#   about 1/3 of the requests go through, you'll want to trigger a reload on the
#   service-proxy container.  Use the `curl` command at the appropriate time
#   during the `ab` test to simulate reloading HAProxy in an actual environment.
#   You may have to up the number "-n" of requests if it happens too quickly.

# Test it
ab -c 10 -n 10000 -H "X-IDS-ENV: dev" "http://127.0.0.1/test/"

# Reload it by editing a watched node on Consul
curl -X PUT 'http://localhost:8500/v1/kv/sd/env/dev/definitions/test-app' --data '{"consumes": ["foo"], "haproxy": {"path": "test"}}'

# Teardown
docker kill service-proxy test-app consul \
  && docker rm service-proxy test-app consul

Known issues