Web service processing phases
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
Next: Endpoints and handlers
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