What is WebHook:
A webhook or a web callback or HTTP push API provides a way to send real time information to other applications. So, when ever a change happens in the source application, it sends this event information to other applications that were configured to listen to such events
How Git WebHook works
As you know git is a public repository (unless you have a local server configured), so in order to send these events to the target client it have to go through internet
In simple words, Git does not know the address ‘localhost’ so cannot send the information
So how to over come this?
Think!!!!!!
1..2..3..4..5
Ok, so the solution is to send these events to a public system and the target application get the information from the public system:
Actual implementation:
But github doesn’t know how to reach Jenkins and other apps.
Work Around:
Here, the github will send the WebHook data to a public server
The Jenkins host system polls for data from the public server
If any event is detected , then Jenkins system triggers the build
Steps…
Navigate to : https://smee.io/:
This is our public server
Click ‘start a new channel’:
Install smee using the command:
npm install --global smee-client
Run smee to poll for events:
copy the url:
Run the below command:
Here, –path shows were to transfer the received packets. The hostname is localhost and its by default. We just have to mention the location of webhook
So, –path /github-webhook/ implies, http://localhost:8000/github-webhook/ (this is the default webhook handle for Jenkins)
Port specifies the port in which the application (Jenkins in this case ) runs.
smee -u https://smee.io/KXVW3UMxLTQ8y9 --path /github-webhook/ --port 8080
Now smee is polling for events from the smee server, and once event is received , it transfers the event to jenkins webhook handle.
Configure webhook in github:
Navigate to githubrepo>settings>webhooks>Add webhooks
Copy the url from smee and paste it in payload url
Change content type as json and make events to ‘Send everything’
Configure Jenkins:
Give git repository name as usual
Set build trigger as github hook
Build the job manually by clicking ‘build’ after creating the job.
Now try commiting new changes to your git repo. You can see that , when ever something changes in git repo, the build starts automatically.
Note: you have manually initiate build first time, after that it works automatically
Reference: https://jenkins.io/blog/2019/01/07/webhook-firewalls/
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