faas - Functions As A Service

This project provides a way to run Docker containers as functions on Swarm Mode.

• Each container has a watchdog process that hosts a web server allowing a JSON post request to be forwarded to a desired process via STDIN. The respose is sent to the caller via STDOUT.
• A gateway provides a view to the containers/functions to the public Internet and collects metrics for Prometheus and in a future version will manage replicas and scale as throughput increases.

Quickstart

Minimum requirements:

• Docker 1.13-RC (to support attachable overlay networks)
• At least a single host in Swarm Mode. (run docker swarm init)

For more information on Swarm mode and configuration please have a look at the [Swarm Mode tutorial](https://docs.docker.com/engine/swarm/swarm-tutorial/).

Check your docker version and upgrade to one of the latest 1.13-RCs from the Docker Releases page. This is already available through the Beta channel in Docker for Mac.

Create an attachable network for the gateway and functions to join

# docker network create --driver overlay --attachable functions

Start the gateway

# docker pull alexellisio/faas-gateway:latest
# docker rm -f gateway;
# docker run -d -v /var/run/docker.sock:/var/run/docker.sock --name gateway -p 8080:8080 \
  --network=functions alexellisio/faas-gateway:latest

Start at least one of the serverless functions:

Here we start an echo service using the cat command found in a shell.

# docker service rm catservice
# docker service create --network=functions --name catservice alexellisio/faas-catservice:latest

Now send an event to the API gateway

• Method 1 - use the service name as a URL:

# curl -X POST --data-binary @$HOME/.ssh/known_hosts -v http://localhost:8080/function/catservice

• Method 2 - use the X-Function header:

# curl -X POST -H 'x-function: catservice' --data-binary @$HOME/.ssh/known_hosts -v http://localhost:8080/

Build your own function

Visit the accompanying blog post to find out how to build your own function in whatever programming language you prefer.

FaaS blog post

Overview

the gateway

This container acts in a similar way to the API Gateway on AWS. Requests can be made to this endpoint with a JSON body.

Incoming requests and routing

There are three options for routing:

• Functions created on the overlay network can be invoked by: http://localhost:8080/function/{servicename}
• Routing automatically detects Alexa SDK requests and forwards to a service name (function) that matches the Intent name
• Routing is enabled through a X-Function header which matches a service name (function) directly.

Features:

• [todo] auto-scaling of replicas as load increases
• [todo] backing off of replicas as load reduces
• [todo] unique URL routes for serverless functions
• instrumentation via Prometheus metrics at GET /metrics

the watchdog

This binary fwatchdog acts as a watchdog for your function. Features:

• Static binary in Go
• Listens to HTTP requests over swarm overlay network
• Spawns process set in fprocess ENV variable for each HTTP connection
• [todo] Only lets processes run for set duration i.e. 500ms, 2s, 3s.
• Language/binding independent

Additional technical debt:

• Must switch over to timeouts for HTTP.post via HttpClient.
• Coverage with unit tests
• Update quick-start to use docker stack deploy
• Have docker stack deploy include a pre-configured Prometheus instance.

Building a development environment:

To use multiple hosts you should push your services (functions) to the Docker Hub or a registry accessible to all nodes.

# docker network create --driver overlay --attachable functions
# git clone https://github.com/alexellis/faas && cd faas
# cd watchdog
# ./build.sh
# cd ../sample-functions/catservice/
# cp ../../watchdog/fwatchdog ./
# docker build -t catservice . ; docker service rm catservice ; docker service create --network=functions --name catservice catservice
# cd ../../
# cd gateway
# docker build -t server . ;docker rm -f server; docker run -v /var/run/docker.sock:/var/run/docker.sock --name server -p 8080:8080 --network=functions server

Accessing the cat (read echo) service:

# curl -X POST -H 'x-function: catservice' --data-binary @$HOME/.ssh/known_hosts -v http://localhost:8080/

# curl -X POST -H 'x-function: catservice' --data-binary @/etc/hostname -v http://localhost:8080/

Prometheus metrics / instrumentation

Standard go metrics and function invocation count / duration are available at http://localhost:8080/metrics/