Deploy straight from Slack using Jenkins and Capistrano

Deploy code by typing ‘/deploy_code_to_dev’ in a Slack channel.


Slack allows you to define slash commands, which will do a POST to a URL that you specify – so you can type ‘/deploy_code_to_dev’ in a Slack channel, and a POST request will trigger a build on Jenkins.

The Jenkins job is configured to run a Capistrano task as the build step – like ‘cap dev deploy’.

The job can be parameterised, so that the task name and target environment can be specified in the trigger URL.


First, install the “Slack Notification” plugins in Jenkins. This allows feedback from Jenkins into a Slack channel to let you know whether the task was successful.

Set up a build project in Jenkins, called something like ‘capistrano-build’. Flag it as parameterised, with ENVIRONMENT, TASK and PARAMS as parameters – these will be used in the capistrano call later.

Specify the git repo where your capistrano tasks are (note that we’re specifying the branch as $ENVIRONMENT, so that we can select a branch like dev, staging etc when we invoke the job):

Generate an authentication token to include with the call to the URL that triggers the build. I used a hex-encoded token to avoid any uncertainty about the encoding of URL parameters:

openssl rand -hex 32

Add a section for triggering the build remotely, using the token:

Set the build environment with a build number:

And configure the build step – this is where we’ll actually invoke the Capistrano command:

Now you can trigger the build by POSTing to the URL:

curl -X POST ""

Set the post-build actions to send some details to Slack – you’ll need to get the integration token from Slack


Now to trigger the build, we’ll add a Slash Command in Slack – these are user-defined commands that you can invoke by typing ‘/’ and your command name, and they can do some useful stuff like calling external URLs.

Add a new slash command, and configure it with a name like ‘/deploy_code_to_dev’ :

Set the Request URL to be the one that we used above in the curl request

Now just type ‘/deploy_code_to_dev’ from a Slack channel, and the slash command will post to the Jenkins build trigger. Results from the build will be posted back into the Slack channel that you configured.

To call a task that needs some extra parameters passed in, you can set up a slack command like:

Jenkins builds of GitLab branches stopped working due to security patch

There have been some security patches to Jenkins recently, which have stopped some plugins from working – in our case, the Gitlab Merge Request Builder Plugin.

Parameters that used to get passed in as part of a trigger to build a branch stopped being passed through.

Errors in the Jenkins build console output looked like this – you can see that ${gitlabSourceBranch} is not being replaced properly with the branch name:

git config remote.refs/remotes/origin/${gitlabSourceBranch}.url # timeout=10

And the log file had lots of entries like this:

May 17, 2016 9:25:33 AM hudson.model.ParametersAction filter
WARNING: Skipped parameter `gitlabSourceBranch` as it is undefined on `knowmalaria-merge`. Set `-Dhudson.model.ParametersAction.keepUndefinedParameters`=true to allow undefined parameters to be injected as environment variables or `-Dhudson.model.ParametersAction.safeParameters=[comma-separated list]` to whitelist specific parameter names, even though it represents a security breach

To get the branches building again, we had to update the parameters that the Jenkins server is started with.

In /etc/init.d/jenkins, set up a list of the parameters that the build will need :

# allow parameters to be passed in to gitlab builds

and pass those parameters to the process at startup:

# --user in daemon doesn't prepare environment variables like HOME, USER, LOGNAME or USERNAME,
# so we let su do so for us now

Then restart your Jenkins server:

sudo service jenkins restart

You may have a different list of parameters that need to be passed to the build – check the ‘parameters’ page for one of your previous builds.

See more description of the original security flaw here:

Search and replace with regex in Sublime Text

One of the things that we do a lot in our Ruby on Rails project is replace old-style Ruby hashes (“hash rockets”) with new style, more compact hashes.

So this

{ :key => "value" }

becomes this

{ key: "value" }

In Sublime Text, you can use a regex in find and replace – like this:


Select the “regex” option (far left), and use the “…” button (middle right) to select “Add Current File” as the scope. Then use the “Replace” button (bottom left) – the prompt will tell you how many instances are going to be replaced.

Of course, if you’re feeling brave, you could do the same find and replace across ALL your files..

There’s some more about the new style here :

Two-Legged OAuth with the Google Drive API in Ruby

Google are discontinuing support for the Documents List API, and moving to the Drive API.

The old API supported authentication with a username and password, but that’s not allowed in the new API. Instead, you need to use OAuth for access.

If you want to have server-to-server authentication, without user interaction, you need a “two-legged” OAuth process, where a token is obtained with an encrypted request and then used for future service requests.

Continue reading “Two-Legged OAuth with the Google Drive API in Ruby”

from_sentence : the opposite of Rails to_sentence

I like the Rails to_sentence method on String class, which converts an array to a comma-separated sentence where the last element is joined by a connector word.

It makes it easy to take a list of names, for example, and make them human-readable, without having to fiddle with join words and last-item-is-special-case stuff:

['one', 'two'].to_sentence          # => "one and two"
['one', 'two', 'three'].to_sentence # => "one, two, and three"

Continue reading “from_sentence : the opposite of Rails to_sentence”