handler

KrakenD - HTTP Handler Plugin Example

This repository provides an example of how to build and inject a Handler Plugin into the KrakenD API Gateway. Follow the steps below to understand how to set up and use the handler plugin.

Overview

The handler plugin, named my-handler-plugin, demonstrates how to create a custom HTTP handler that can be integrated into KrakenD. The plugin replaces the default HTTP handler by adding custom logic before and after the request is processed.

File Structure

• handler.go: The main plugin code that implements the RegisterHandler interface.
• go.mod: The Go module file.
• Makefile: Instructions for building the plugin using Docker.

Prerequisites

• Go
• Docker
• KrakenD API Gateway (version 2.x)

Building the Plugin

You should build the plugin using the KrakenD Docker builder image. The Makefile includes targets for different architectures.

Steps

1. Clone the Repository:

   git clone https://github.com/krakend/examples.git
   cd examples/plugins/handler

2. Build for Different Architectures:

   • For amd64:

     make amd64

   • For arm64:

     make arm64

   • For linux_amd64 (non-docker):

     make linux_amd64

   • For linux_arm64 (non-docker):

     make linux_arm64

Plugin Configuration

To use the plugin in your KrakenD configuration, add it under the extra_config section of your krakend.json file.

Example Configuration

{
   "version": 3,
   "plugin": {
      "pattern": ".so",
      "folder": "/etc/krakend/plugins"
   },
   "host": ["http://localhost:8080/"],
   "debug_endpoint": true,
   "endpoints": [
      {
         "endpoint": "/example",
         "backend": [
            {
               "url_pattern": "/__debug/"
            }
         ]
      }
   ],
   "extra_config": {
      "plugin/http-server": {
         "name": ["my-handler-plugin"],
         "my-handler-plugin": {
            "someOption": "some-value"
         }
      }
   }
}

Logger Interface

The plugin supports a logger interface to help with debugging and logging messages.

Logger Methods

• Debug(v ...interface{})
• Info(v ...interface{})
• Warning(v ...interface{})
• Error(v ...interface{})
• Critical(v ...interface{})
• Fatal(v ...interface{})

Custom Logic

The my-handler-plugin adds custom logic by wrapping the default HTTP handler. It logs the configuration option and then processes the request using the default handler.

Usage

1. Build the plugin using the appropriate make target. The plugin will be generated under the plugins folder.
2. Test your KrakenD using Docker, for instance:

docker run --rm -it --name krakend -p 8080:8080 -v "$PWD:/etc/krakend" devopsfaith/krakend

3. Send an example call

curl -iG 'http://localhost:8080/example'

For more details on handler plugins and extending KrakenD, refer to the official documentation.