Web service processing phases

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In Granitic, the components and processes that are used to service an HTTP request to your application are organised into a series of ‘phases’. Although the order of these phases is fixed, most of them can be customised, disabled or even swapped out for your own implementation.

A request is initially handled by Granitic’s HTTP server facility then passed on to a component that implements httpendpoint.Provider and supports the incoming request’s URL and HTTP method. In the vast majority of cases that component will be an instance of Granitic’s built-in handler.WsHandler.

Your application will associate a logic component with each handler to perform business logice and build a response.

Phases

Component Step Purpose
HTTP Server Instrumentation Begin timing/metric gathering if your application supports instrumentation
Load management Reject request if too busy/suspended
Request identification Assign a unique ID to the request if supported by your application
Matching Attempt to match the request’s path and HTTP method to a handler
Version routing If your application supports version routing the correct handler for the request version is found
Handler Authentication If your application supports identity and access management the request caller is authenticated
Authorisation If the caller has been authenticated, their permission to access this functionality is checked
Data extraction Data from the request body, path and query parameters is parsed into a struct
Validation The extracted data is validated to confirm that it is ready to be processed
Application logic Processing The application logic component performs the actual function of the web service
Response construction A Go struct is populated with data that will form the response to the request
Handler Response serialisation Serialise the response struct (normally to JSON or XML)
HTTP Server Request finalisation Instrumentation ended and HTTP request closed

Error handling

The above represents the ‘happy path’ for a request. Most of the phases can terminate early triggering automatic error handling


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