FAQ¶

Optional Component¶

You might need to express the fact that some of your dependencies are optional. This often happens for components that interact with many other components if available (that is, if they were included at compile time). This allows your component to interact with each other without forcing their inclusion in the current binary.

The optional.Option type answers this need.

For examples, consider the metadata components that are included in multiple binaries (core-agent, DogStatsD, etc.). These components use the sysprobeconfig component if it is available. sysprobeconfig is available in the core-agent but not in DogStatsD.

To do this in the metadata component:

type Requires struct {
    SysprobeConf optional.Option[sysprobeconfig.Component]
    [...]
}

func NewMetadata(deps Requires) (metadata.Component) {
    if sysprobeConf, found := deps.SysprobeConf.Get(); found {
        // interact with sysprobeconfig
    }
}

The above code produces a generic component, included in both core-agent and DogStatsD binaries, that can interact with sysprobeconfig without forcing the binaries to compile with it.

You can use this pattern for every component, since all components provide Fx with a conversion function to convert their Component interfaces to optional.Option[Component] (see creating components).