Bash Functions as a Service

Goal : Run bash scripts as serverless functions.

Blog post

There is a more detailed blog post here.

OpenFaaS is very straight forward to setup. This setup uses a local Docker Swarm. Instructions can be found here.

Follow the instructions here. When you reach the "2.1 nmap" section then you can try the following.

Setup

Create scaffolding

faas new --lang dockerfile bash --prefix tshaw

The prefix will be included in the container image name. For example the image for this function will be called : tshaw/bash:latest. Without the prefix the image will be named bash:latest and this may cause issues if there is a publicly available image with the same name.

Add in bash script and update Dockerfile

Copy test.sh into the "bash" directory.

Update Dockerfile to include :

RUN apk add --no-cache bash whois iputils 
 
ADD test.sh /tmp/test.sh

ENV fprocess="xargs bash /tmp/test.sh"

Build and Deploy

faas build -f bash.yml  && faas deploy -f bash.yml

Test it works

echo -n "google.com" | faas invoke bash

echo -n "bbc.com" | faas invoke bash

echo -n "amazon.com" | faas invoke bash

Example Output :

=========================================
Running WHOIS for : google.com
=========================================
Name Server: ns4.google.com
Name Server: ns2.google.com
Name Server: ns3.google.com
Name Server: ns1.google.com
=========================================
Ping Check
=========================================
PING google.com (74.125.193.100) 56(84) bytes of data.
64 bytes from ig-in-f100.1e100.net (74.125.193.100): icmp_seq=1 ttl=46 time=14.0 ms

--- google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 14.004/14.004/14.004/0.000 ms
=========================================

Add more replicas to handle incoming requests

docker service scale bash=3

bash scaled to 3
overall progress: 3 out of 3 tasks 
1/3: running   [==================================================>] 
2/3: running   [==================================================>] 
3/3: running   [==================================================>] 
verify: Service converged 

Verify the hostname changes when running this a number of times :

echo -n "amazon.com" | faas invoke bash

Selecting different scripts from same function container

In the example above we have put one script into a container image and invoked it as a FaaS. If you have a bunch of similar scripts, they are small and share the same dependencies then you could put them into the same container image.

There is an example here. We use a small piece of bash as the top level function and then select the function we require when invoking the collection function.

Build and deploy the "Collection" function

faas build collection.yml  && faas deploy -f collection.yml

Invoke different functions from the collection function

Invoke Weather function

echo -n "--function weather --argument Dublin" | faas invoke collection

Invoke Movie function

echo -n "--function movies --argument Seven" | faas invoke collection

Invoke cryptocurrency function

echo -n "--function cryptocurrency" | faas invoke collection

Invoke lyrics function

echo -n "--function lyrics --argument \"-a U2 -s Beautiful Day\"" | faas invoke collection

This method might be frowned upon but it's convenient for evaluation purposes.

tomwillfixit / BashOpenFaaS