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0798f9fac8
* Adds root level middleware * Added todo * Better way for extensions to be added. * Bad conflict merge?
95 lines
3.0 KiB
Markdown
95 lines
3.0 KiB
Markdown
# Writing Extensions
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Fn is extensible so you can add custom functionality and extend the project without needing to modify the core.
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There are multiple ways to extend the functionality of Fn.
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1. Listeners - listen to API events such as a route getting updated and react accordingly.
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1. Middleware - a chain of middleware is executed before an API handler is called.
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1. Add API Endpoints - extend the default Fn API.
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To create an extension, there are just a couple of rules to follow.
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* All config should be via ENV vars.
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## Code
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Your extension code needs to register itself with an `init()` method which states it's name and a function
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to be called during setup:
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```go
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func init() {
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server.RegisterExtension(&fnext.Extension{
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Name: "logspam",
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Setup: setup, // Fn will call this during startup
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})
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}
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func setup(s *fnext.ExtServer) error {
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// Add all the hooks you extension needs here
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s.AddCallListener(&LogSpam{})
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}
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```
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## Listeners
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Listeners are the main way to extend Fn.
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The following listener types are supported:
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* App Listeners - [GoDoc](https://godoc.org/github.com/fnproject/fn/api/server#AppListener)
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* Call Listeners - [GoDoc](https://godoc.org/github.com/fnproject/fn/api/server#CallListener)
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### Creating a Listener
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You can easily use add listeners by creating a struct with valid methods satisfying the interface
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for the respective listener, adding it to `main.go` then compiling.
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Example:
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```go
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package main
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import (
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"context"
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"github.com/fnproject/fn/api/server"
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"github.com/fnproject/fn/api/models"
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)
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type myCustomListener struct{}
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func (c *myCustomListener) BeforeAppCreate(ctx context.Context, app *models.App) error { return nil }
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func (c *myCustomListener) AfterAppCreate(ctx context.Context, app *models.App) error { return nil }
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func (c *myCustomListener) BeforeAppUpdate(ctx context.Context, app *models.App) error { return nil }
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func (c *myCustomListener) AfterAppUpdate(ctx context.Context, app *models.App) error { return nil }
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func (c *myCustomListener) BeforeAppDelete(ctx context.Context, app *models.App) error { return nil }
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func (c *myCustomListener) BeforeAppDelete(ctx context.Context, app *models.App) error { return nil }
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function main () {
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srv := server.New(/* Here all required parameters to initialize the server */)
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srv.AddAppListener(myCustomListener)
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srv.Run()
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}
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```
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## Middleware
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Middleware enables you to add functionality to every API request. For every request, the chain of Middleware will be called
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in order, allowing you to modify or reject requests, as well as write output and cancel the chain.
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NOTES:
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* middleware is responsible for writing output if it's going to cancel the chain.
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See examples of this in [examples/middleware/main.go](../../examples/middleware/main.go).
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## Adding API Endpoints
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You can add API endpoints to the Fn server by using the `AddEndpoint` and `AddEndpointFunc` methods.
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See examples of this in [examples/extensions/main.go](../../examples/extensions/main.go). |