Medela Gateway

API Gateway for PT. Medela Potentia interview task. This custom gateway is inspired by KrakenD

Installation

Clone this repository, enter to project root directory and run this command to build the project:
make build

This command will build the project binary as medela-gateway

To run the build with default port (:8080) and config, execute this command:
make run

This command will run the app and will also trying to find default config config.json. You can provide the config file by creating one.

To run the app with custom config file, run the binary as follows:
./medela-gateway -c {config_file}.json

with {config_file} as the file name, example:
./medela-gateway -c my_config.json

To run with custom port, run the binary as follows:
./medela-gateway -p {port}

with {port} as the port number, example: ./medela-gateway -p 9000 -c config.json

Configuration file overview

A configuration file is needed to run the app so that it can function properly. The configuration file consist of registered endpoints pointed to determined server or backend, example:

{
    "endpoints": [
        {
            "endpoint": "/api/v1/user/:id",
            "method": "GET",
            "backend": {
                "host": "https://userdata.com",
                "url_pattern": "/user/:id",
                "method": "GET"
            }
        }
    ]
}

From above example, the config file is telling the gateway to add route to GET https://userdata.com/user/:id by endpoint /api/v1/user/:id. The :id is path parameter, endpoint and backend.url_pattern must has the same path parameters (if any, this is optional) or the http requests will not propely work

Currently the gateway can only support JSON response data because of the time constraints to complete this project

Add an endpoint

To add an endpoint, append a new object inside endpoints on the config file, example:

{
    "endpoints": [
        {
            "endpoint": "/api/v1/user/:id",
            "method": "GET",
            "backend": {
                "host": "https://userdata.com",
                "url_pattern": "/user/:id",
                "method": "GET"
            }
        }
    ]
}

The configuration attributes of endppoints are:

Attribute name	Mandatory?	Type	Description
`endpoint`	Y	`string`	The URL you want to expose. You can add path parameter to it by using preffix `:`, example: `/product/:label`
`method`	Y	`string`	The supported method to request this endpoint
`backend`	Y	`object`	The server that will handle the request to this endpoint. See the backend configuration
`middlewares`	N	`array`	Collection of middlewares. When present, every request to this endpoint will be passed through the middlewares first. See middleware configuration

Backend configuration

A backend is the server that resposinble to handle a request to an endpoint. Currently every endpoint can only support exactly 1 backend server. Example:

{
    "host": "https://userdata.com",
    "url_pattern": "/user/:id",
    "method": "GET"
}

Attributes of backend are:

Attribute name	Mandatory?	Type	Description
`host`	Y	`string`	The server/backend host, can be a domain or IP. You need to specify the scheme as the preffix, example: `https://foo.com`, `foo.com` is not a valid value
`url_pattern`	Y	`string`	The URL that will handle the request to an endpoint
`method`	Y	`string`	The supported method by this backend

Middleware configuration

A middleware act as filter for incoming requests to an endpoint, this can be used to verify the validity of a request, for example user authorization. To add a middleware, append the middleware object to endpoints.middlewares array, example:

{
    "endpoint": "/api/v1/product",
    "method": "GET",
    "backend": {
        "host": "http://myproducts.com",
        "url_pattern": "/product",
        "method": "GET"
    },
    "middlewares": [
        {
            "host": "http://myproducts.com",
            "url_pattern": "/auth",
            "merge_response_body": true,
            "merge_response_header": true
        }
    ]
}

The attributes for a middleware are:

Attribute name	Mandatory?	Type	Description
`host`	Y	`string`	The middleware server host, can be a domain or IP. You need to specify the scheme as the preffix, example: `https://foo.com`, `foo.com` is not a valid value
`url_pattern`	Y	`string`	The URL that will filter the incoming requests to an endpoint
`merge_response_body`	N	`boolean`	If true, the response body from middleware will be merged into endpoint backend response body. This is only supported for JSON type response
`merge_response_header`	N	`boolean`	If true, the response headers from middleware will be merged into endpoint backend response headers. All canonical headers will NOT be merged, only custom headers will