webhookd

A very simple webhook server to launch shell scripts.

Installation

Run the following command:

$ go get -v github.com/ncarlier/webhookd

Or download the binary regarding your architecture:

$ sudo curl -s https://raw.githubusercontent.com/ncarlier/webhookd/master/install.sh | bash

Or use Docker:

$ docker run -d --name=webhookd \
  -v ${PWD}/scripts:/var/opt/webhookd/scripts \
  -p 8080:8080 \
  ncarlier/webhookd \
  webhookd --scripts=/var/opt/webhookd/scripts

Note that this image extends docker:dind Docker image. Therefore you are able to interact with a Docker daemon with yours shell scripts.

Configuration

You can configure the daemon by:

Setting environment variables:

Variable	Default	Description
APP_LISTEN_ADDR	:8080	HTTP service address
APP_PASSWD_FILE	.htpasswd	Password file for HTTP basic authentication
APP_NB_WORKERS	2	The number of workers to start
APP_HOOK_TIMEOUT	10	Hook maximum delay before timeout (in second)
APP_SCRIPTS_DIR	./scripts	Scripts directory
APP_SCRIPTS_GIT_URL	none	GIT repository that contains scripts (Note: this is only used by the Docker image or by using the Docker entrypoint script)
APP_SCRIPTS_GIT_KEY	none	GIT SSH private key used to clone the repository (Note: this is only used by the Docker image or by using the Docker entrypoint script)
APP_LOG_DIR	/tmp (OS temp dir)	Directory to store execution logs
APP_NOTIFICATION_URI	none	Notification configuration URI
APP_DEBUG	false	Output debug logs

Using command parameters:

Parameter	Default	Description
-l <address> or --listen <address>	:8080	HTTP service address
-p or --passwd <htpasswd file>	.htpasswd	Password file for HTTP basic authentication
-d or --debug	false	Output debug logs
--nb-workers <workers>	2	The number of workers to start
--scripts <dir>	./scripts	Scripts directory
--timeout <timeout>	10	Hook maximum delay before timeout (in second)
--notification-uri <uri>		Notification configuration URI
--log-dir <dir>	/tmp	Directory to store execution logs

Usage

Directory structure

Webhooks are simple scripts dispatched into a directory structure.

By default inside the ./scripts directory. You can override the default using the APP_SCRIPTS_DIR environment variable.

Example:

/scripts
|--> /github
  |--> /build.sh
  |--> /deploy.sh
|--> /ping.sh
|--> ...

Webhook URL

The directory structure define the webhook URL.

If the script exists, the output the will be streamed to the HTTP response.

The streaming technology depends on the HTTP method used. With POST the response will be chunked. With GET the response will use Server-sent events.

Example:

The script: ./scripts/foo/bar.sh

#!/bin/bash

echo "foo foo foo"
echo "bar bar bar"

Output using POST (Chunked transfer encoding):

$ curl -v -XPOST http://localhost:8080/foo/bar
< HTTP/1.1 200 OK
< Content-Type: text/plain; charset=utf-8
< Transfer-Encoding: chunked
< X-Hook-Id: 7
foo foo foo
bar bar bar
done

Output using GET (Server-sent events):

$ curl -v -XGET http://localhost:8080/foo/bar
< HTTP/1.1 200 OK
< Content-Type: text/event-stream
< Transfer-Encoding: chunked
< X-Hook-Id: 8
data: foo foo foo

data: bar bar bar

data: done

Webhook parameters

You have several way to provide parameters to your webhook script:

• URL query parameters and HTTP headers are converted into environment variables. Variable names follows "snakecase" naming convention. Therefore the name can be altered.

  ex: CONTENT-TYPE will become content_type.

• When using POST, body content (text/plain or application/json) is transmit to the script as parameter.

Example:

The script:

#!/bin/bash

echo "Query parameter: foo=$foo"
echo "Header parameter: user-agent=$user_agent"
echo "Script parameters: $1"

The result:

$ curl --data @test.json http://localhost:8080/echo?foo=bar
Query parameter: foo=bar
Header parameter: user-agent=curl/7.52.1
Script parameter: {"foo": "bar"}
done

Webhook timeout configuration

By default a webhook has a timeout of 10 seconds. This timeout is globally configurable by setting the environment variable: APP_HOOK_TIMEOUT (in seconds).

You can override this global behavior per request by setting the HTTP header: X-Hook-Timeout (in seconds).

Example:

$ curl -H "X-Hook-Timeout: 5" http://localhost:8080/echo?foo=bar

Webhook logs

As mentioned above, web hook logs are stream in real time during the call. However, you can retrieve the logs of a previous call by using the hook ID: http://localhost:8080/<NAME>/<ID>

The hook ID is returned as an HTTP header with the Webhook response: X-Hook-ID

Example:

$ # Call webhook
$ curl -v http://localhost:8080/echo?foo=bar
...
< HTTP/1.1 200 OK
< Content-Type: text/event-stream
< X-Hook-Id: 2
...
$ # Retrieve logs afterwards
$ curl http://localhost:8080/echo/2

Post hook notifications

The output of the script is collected and stored into a log file (configured by the APP_LOG_DIR environment variable).

Once the script is executed, you can send the result and this log file to a notification channel. Currently, only two channels are supported: Email and HTTP.

Notifications configuration can be done as follow:

$ export APP_NOTIFICATION_URI=http://requestb.in/v9b229v9
$ # or
$ webhookd --notification-uri=http://requestb.in/v9b229v9

Note that only the output of the script prefixed by "notify:" is sent to the notification channel. If the output does not contain a prefixed line, no notification will be sent.

Example:

#!/bin/bash

echo "notify: Hello World" # Will be notified
echo "Goodbye"             # Will not be notified

You can overide the notification prefix by adding prefix as a query parameter to the configuration URL.

Example: http://requestb.in/v9b229v9?prefix="foo:"

HTTP notification

Configuration URI: http://example.org

Options (using query parameters):

• prefix: Prefix to filter output log

The following JSON payload is POST to the target URL:

{
  "id": "42",
  "name": "echo",
  "text": "foo\nbar...\n",
  "error": "Error cause... if present",
}

Note that because the payload have a text attribute, you can use a Mattermost webhook endpoint.

Email notification

Configuration URI: mailto:foo@bar.com

Options (using query parameters):

• prefix: Prefix to filter output log
• smtp: SMTP host to use (by default: localhost:25)
• from: Sender email (by default: webhookd <noreply@nunux.org>)

Authentication

You can restrict access to webhooks using HTTP basic authentication.

To activate basic authentication, you have to create a htpasswd file:

$ # create passwd file the user 'api'
$ htpasswd -B -c .htpasswd api

This command will ask for a password and store it in the htpawsswd file.

Please note that by default, the daemon will try to load the .htpasswd file.

But you can override this behavior by specifying the location of the file:

$ APP_PASSWD_FILE=/etc/webhookd/users.htpasswd
$ # or
$ webhookd -p /etc/webhookd/users.htpasswd

Once configured, you must call webhooks using basic authentication:

$ curl -u api:test -XPOST "http://localhost:8080/echo?msg=hello"

---