Groups

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Uber-FX group is a feature that allows you to consume and produce multiple values of the same type. This makes it easier to influence/configure different instances.

Mortar has different groups, but we will focus on one of them here.

Internal HTTP Handlers

// InternalHTTPHandlers - Internal Http Handlers group. Mortar comes with several internal handlers, you can add yours.
InternalHTTPHandlers = partial.FxGroupInternalHTTPHandlers

//InternalHTTPHandlerFunctions - Internal Http Handler Functions group. Similar toInternalHttpHandlers but for functions
InternalHTTPHandlerFunctions = partial.FxGroupInternalHTTPHandlerFunctions

Build Information

Similar to everything else in Uber-FX, to register a new instance into a fx.Group you need to create a Constructor.

We will look at one of the internal handlers: Build Information.

Build Information

In this example we want to register a new internal ["/<path>/<pattern>" -> http.HandlerFunc] pair.

Let’s start by defining a constructor that will return http.HandlerFunc:

func (s *selfHandlerDeps) BuildInfo() http.HandlerFunc {
  return func(w http.ResponseWriter, req *http.Request) {
  information := mortar.GetBuildInformation(true) // using true here will insert a default value if there is none
  if err := json.NewEncoder(w).Encode(information); err != nil {
    w.WriteHeader(http.StatusInternalServerError)
    s.Logger.WithError(err).Warn(nil, "failed to serve build info")
  }
  }
}

Create an HTTPHandlerPatternPair. This is the part where you define on what path this handler will be served:

// SelfHandlers this service information handlers
func SelfHandlers(deps selfHandlerDeps) []partial.HTTPHandlerPatternPair {
  return []partial.HTTPHandlerPatternPair{
  {Pattern: "/self/build", Handler: deps.BuildInfo()},
  ...
  }
}

Tell Uber-FX that we want this instance of HTTPHandlerPatternPair added to the groups.InternalHTTPHandlerFunctions group.

func InternalSelfHandlersFxOption() fx.Option {
  return fx.Provide(
  fx.Annotated{
    Group:  groups.InternalHTTPHandlers + ",flatten",
    Target: handlers.SelfHandlers,
  })
}

Lastly, in your application you need to provide the above InternalSelfHandlersFxOption() option to Uber-FX graph, here you can see how it’s done in the demo.
```
return fx.New(
  ...
  InternalSelfHandlersFxOption(),
  ...
)
```

Tests