Hookah

Hookah is a simple server for GitHub Webhooks that forwards the hooks message to any series of scripts, be they PHP, Ruby, Python or even straight up shell.

It simply passes the message on to the STDIN of any script.

Installation

From Source

Building v2 requires Go module support, available in Go 1.9.7+, 1.10.3+, 1.11+ or newer.

go get -u -v github.com/donatj/hookah/cmd/hookah

From Binary

see: Releases.

Basic Usage

When receiving a Webhook request from GitHub, Hookah checks {server-root}/{vendor}/{repo}/{X-GitHub-Event}/* for any executable scripts, and executes them sequentially passing the JSON payload to it's standard in.

This allows actual hook scripts to be written in any language you prefer.

For example, a script server/donatj/hookah/push/log.rb would be executed every time a "push" event Webhook was received from GitHub on the donatj/hookah repo.

Example Hook Scripts

bash + jq

#!/bin/bash

set -e

json=`cat`
ref=$(<<< "$json" jq -r .ref)

echo "$ref"
if [ "$ref" == "refs/heads/master" ]
then
        echo "Ref was Master"
else
        echo "Ref was not Master"
fi

PHP

#!/usr/bin/php
<?php

$input = file_get_contents("php://stdin");
$data  = json_decode($input, true);

print_r($data);

Note

Don't forget your scripts need to be executable. This means having the executable bit set ala chmod +x <script filename>, and having a shebang pointing to your desired interpreter, i.e. #!/bin/bash

Documentation

Standard input (stdin) contains the unparsed JSON body of the request.

Execution

The server root layout looks like {server-root}/{vendor}/{repo}/{X-GitHub-Event}/{script-name}

Scripts are executed at each level, in order of least specific to most specific. At an individual level, the execution order is file system specific and must not be depended upon.

A directory at the vendor or repo level named @@ will behave as a wildcard. As such a file named server-root/donatj/@@/pull_request_review_comment/script.sh would execute for all of @donatj's pull_request_review_comment events regardless of repo.

Error Handling

Error handlers are scripts prefixed with @@error. and function similarly to standard scripts. Error handlers however are only triggered when the executiono of a normal script returns a non-zero exit code.

Error handlers like normal scripts trigger in order up from the root to the specificity level of the script.

Example

Consider the following server file system.

├── @@error.rootlevel.sh
├── run-for-everything.sh
└── donatj
    ├── @@error.userlevel.sh
    ├── run-for-donatj-repos.sh
    ├── @@
    │   └── pull_request_review_comment
    │       └── all-of-donatjs-pr-comments.sh
    └── hookah
        └── pull_request_review_comment
            ├── @@error.event-level.sh
            ├── likes-to-fail.sh
            └── handle-review.php

The execution order of a pull_request_review_comment event is as follows:

run-for-everything.sh
donatj/run-for-donatj-repos.sh
donatj/hookah/pull_request_review_comment/likes-to-fail.sh
donatj/hookah/pull_request_review_comment/handle-review.php
donatj/@@/pull_request_review_comment/all-of-donatjs-pr-comments.sh

Now let's consider if likes-to-fail.sh lives up to it's namesake and returns a non-zero exit code. The execution order then becomes:

run-for-everything.sh
donatj/run-for-donatj-repos.sh
donatj/hookah/pull_request_review_comment/likes-to-fail.sh
@@error.rootlevel.sh
@@error.userlevel.sh
@@error.event-level.sh
donatj/hookah/pull_request_review_comment/handle-review.php
donatj/@@/pull_request_review_comment/all-of-donatjs-pr-comments.sh

In contrast, imagining donatj/run-for-donatj-repos.sh returned a non-zero status, the execution would look as follows:

run-for-everything.sh
donatj/run-for-donatj-repos.sh
@@error.rootlevel.sh
@@error.userlevel.sh
donatj/hookah/pull_request_review_comment/likes-to-fail.sh
donatj/hookah/pull_request_review_comment/handle-review.php
donatj/@@/pull_request_review_comment/all-of-donatjs-pr-comments.sh

Environment Reference

All Executions

GITHUB_EVENT : The contents of the X-Github-Event header.

GITHUB_DELIVERY : The contents of the X-GitHub-Delivery header. A Unique ID for the Given Request

Error Handler Executions

HOOKAH_EXEC_ERROR_FILE : The path to the executable that failed to execute.

HOOKAH_EXEC_ERROR : The error message received while trying to execute the script.

HOOKAH_EXEC_EXIT_STATUS : The exit code of the script. This may not be defined in certain cases where execution failed entirely.