mths : sdrbrg ;

# helpers in the kitchen

When writing tests using RSpec, I prefer to use shared_context and shared_examples for integration setup and for testing shared behaviour, respectively.

When I started out with writing integration tests for my kafka cookbook using serverspec, I wanted to share tests between different suites as they were testing different init systems, but the tests could be heavily refactored to just depend on some shared variables rather than duplicating all of the test cases. It was however not immediately clear how one would go about sharing files between different suites.

After quite some digging I found a bit of information (I think in an old issue or pull request though I no longer have any links handy) that mentioned having a helpers directory in test/integration for sharing files between suites.

So it’s just a matter of creating a helpers directory and the necessary busser specific subdirectory, adding some files and you’re good to go. They’ll even be available on the $LOAD_PATH, so it’s easy to just require a spec_helper or the alike in the actual spec files.

Since v1.2.1 of test-kitchen it’s also possible to create directories in the helpers directory (I tend to keep shared code in a support directory for example).

For reference my kafka cookbook is over here, and more specifically the helpers directory (and serverspec subdirectory) is [over here] (

19 Feb 2016 / test-kitchen chef rspec

# raw sns fanout to sqs

The other day I was messing around a bit with AWS SNS and SQS, more specifically I wanted to send messages to a SNS topic and have the messages fanout to a couple of SQS queues (as mentioned in the Common SNS Scenarios documentation).

It’s simple enough to connect a SNS topic with a SQS queue:

$ aws sns subscribe --topic-arn $SNS_TOPIC_ARN \
                    --protocol sqs \
                    --notification-endpoint $SQS_QUEUE_ARN

However, the messages sent from SNS to SQS end up on a format that’s pretty far from what I wanted:

$ aws sns publish --topic-arn $SNS_TOPIC_ARN --message '{"hello": "world"}'
$ aws sqs receive-message --queue-url $SQS_QUEUE_URL
  "Messages": [
      "Body": "{\n  \"Type\" : \"Notification\",\n  \"MessageId\" : \"42e88f9d-6436-555e-aa9e-c0a7b128eeb8\",\n  \"TopicArn\" : \"arn:aws:sns:eu-west-1:123456789000:test\",\n  \"Message\" : \"{\\\"hello\\\": \\\"world\\\"}\",\n  \"Timestamp\" : \"2016-02-14T19:17:50.008Z\",\n  \"SignatureVersion\" : \"1\"\n}"

I abbreviated the message a bit, but it’s clear that the full SNS message has been JSON encoded and put into the Body of the SQS message.

So what I really wanted was to simply have the messages forwarded from SNS to SQS, without any surprises. Turns out it’s actually possible to achieve exactly that, though I had a hard time finding it in the documentation (not exactly sure if I even found it in the documentation). The trick is to enable the RawMessageDelivery property of the SNS subscription, for example using aws:

$ aws sns set-subscription-attributes --subscription-arn $SNS_SUBSCRIPTION_ARN \
                                      --attribute-name RawMessageDelivery \
                                      --attribute-value true
14 Feb 2016 / aws sns sqs

# checking shell scripts on travis

Whenever I write shell scripts (usually in Bash) I find it a good practice to run shellcheck to make sure that I haven’t done any obvious mistakes, such as forgetting to quote variables (which happens every now and then).

When I was tinkering with ddns-route53 I thought that it would be nice if Travis could run shellcheck for me. I had some trouble with getting shellcheck installed, but eventually found a solution after hopping through a bunch of GitHub issues (don’t even know where I ended up).

The following .travis.yml should get you up and running in no time:

language: bash
sudo: required
dist: trusty
  - echo "deb trusty-backports universe" | sudo tee -a /etc/apt/sources.list
  - sudo apt-get update -qq
  - sudo apt-get install shellcheck -y
  - shellcheck $FILENAME

$FILENAME could also be replaced with a glob or something like $(find . -maxdepth 1 -type f -executable) if you have several files that needs to be checked.

Speaking of shell scripts, I sometimes find myself returning to Thoughtbot’s The Unix Shell’s Humble If blog post when I forget the how’s and why’s of constructing an if statement in Bash.