Using the Per-Endpoint Plugin with Tyk OAS APIs

The per-endpoint custom plugin provides the facility to attach a custom Go plugin at the end of the request processing chain. This plugin allows you to add custom logic to the processing flow for the specific endpoint without adding to the processing complexity of other endpoints. It can terminate the request if required, and provides a Virtual Endpoint style capability using the Go language, rather than JavaScript (as supported by the virtual endpoint middleware).

The middleware is configured in the Tyk OAS API Definition. You can do this via the Tyk Dashboard API or in the API Designer.

If you’re using the legacy Tyk Classic APIs, then check out the Tyk Classic page.

Configuring the middleware in the Tyk OAS API Definition

The design of the Tyk OAS API Definition takes advantage of the operationId defined in the OpenAPI Document that declares both the path and method for which the middleware should be added. The path can contain wildcards in the form of any string bracketed by curly braces, for example {user_id}. These wildcards are so they are human readable and do not translate to variable names. Under the hood, a wildcard translates to the “match everything” regex of: (.*).

The endpoint plugin middleware (postPlugins) can be added to the operations section of the Tyk OAS Extension (x-tyk-api-gateway) in your Tyk OAS API Definition for the appropriate operationId (as configured in the paths section of your OpenAPI Document).

The postPlugins object has the following configuration:

• enabled: enable the middleware for the endpoint
• functionName: this is the name of the Go function that will be executed when the middleware is triggered
• path: the relative path to the source file containing the compiled Go code

You can chain multiple plugin functions in an array. Tyk will process them in the order they appear in the API definition.

For example:

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{
    "components": {},
    "info": {
        "title": "example-endpoint-plugin",
        "version": "1.0.0"
    },
    "openapi": "3.0.3",
    "paths": {
        "/anything": {
            "get": {
                "operationId": "anythingget",
                "responses": {
                    "200": {
                        "description": ""
                    }
                }
            }
        }
    },
    "x-tyk-api-gateway": {
        "info": {
            "name": "example-endpoint-plugin",
            "state": {
                "active": true
            }
        },
        "upstream": {
            "url": "http://httpbin.org/"
        },          
        "server": {
            "listenPath": {
                "value": "/example-endpoint-plugin/",                
                "strip": true
            }
        },      
        "middleware": {
            "operations": {
                "anythingget": {
                    "postPlugins": [
                        {
                            "enabled": true,
                            "functionName": "myUniqueFunctionName",
                            "path": "/middleware/myPlugin.so"
                        }
                    ]
                }
            }
        }
    }
}

In this example the per-endpoint custom plugin middleware has been configured for HTTP GET requests to the /anything endpoint. For any call made to this endpoint, Tyk will invoke the function myUniqueFunctionName in the file located at /middleware/myPlugin.so.

The configuration above is a complete and valid Tyk OAS API Definition that you can import into Tyk to try out the per-endpoint custom plugin middleware.

Configuring the middleware in the API Designer

Adding a per-endpoint custom plugin to your API endpoints is easy when using the API Designer in the Tyk Dashboard, simply follow these steps:

Step 1: Add an endpoint

From the API Designer add an endpoint that matches the path and method to which you want to apply the middleware.

Step 2: Select the Go Post-Plugin middleware

Select ADD MIDDLEWARE and choose Go Post-Plugin from the Add Middleware screen.

Step 3: Configure the middleware

You must provide the path to the compiled plugin and the name of the Go function that should be invoked by Tyk Gateway when the middleware is triggered.

Step 4: Save the API

Select ADD MIDDLEWARE to save the middleware configuration. Remember to select SAVE API to apply the changes.