type Application interface {
    consumer.Application

    // NewConfig returns a new, zero-valued Config instance.
    // Main calls NewConfig to obtain a new instance of the Application's
    // custom configuration type. It will next use `go-flags` to parse
    // command-line and environment flags into the provide Config, in order
    // to provide the Application with a complete configuration.
    NewConfig() Config
    // InitApplication initializes the Application.
    // Main calls InitApplication after parsing the Config and binding
    // HTTP and gRPC servers, but before announcing this process's
    // MemberSpec.
    //
    // InitApplication is a good opportunity to register additional gRPC
    // services or perform other initialization.
    InitApplication(InitArgs) error
}

type BaseConfig struct {
    Consumer struct {
        mbp.ServiceConfig
        Limit uint32 `long:"limit" env:"LIMIT" default:"32" description:"Maximum number of Shards this consumer process will allocate"`
    }   `group:"Consumer" namespace:"consumer" env-namespace:"CONSUMER"`

    Broker struct {
        mbp.ClientConfig
        FileRoot string `long:"file-root" env:"FILE_ROOT" description:"Local path which roots file:// fragment URLs which are being directly read (optional)"`
    }   `group:"Broker" namespace:"broker" env-namespace:"BROKER"`

    Etcd struct {
        mbp.EtcdConfig

        Prefix string `long:"prefix" env:"PREFIX" default-mask:"/gazette/consumers/app-name-and-release" description:"Etcd prefix for the consumer group"`
    }   `group:"Etcd" namespace:"etcd" env-namespace:"ETCD"`

    Log         mbp.LogConfig         `group:"Logging" namespace:"log" env-namespace:"LOG"`
    Diagnostics mbp.DiagnosticsConfig `group:"Debug" namespace:"debug" env-namespace:"DEBUG"`
}

type Config interface {
    GetBaseConfig() BaseConfig
}

type InitArgs struct {
    // Context of the service. Typically this is context.Background(),
    // but tests may prefer to use a scoped context.
    Context context.Context
    // Config previously returned by NewConfig, and since parsed into.
    Config Config
    // Server is a dual HTTP and gRPC Server. Applications may register
    // APIs they implement against the Server mux.
    Server *server.Server
    // Service of the consumer. Applications may use the Service to power Shard
    // resolution, request proxying, and state inspection.
    Service *consumer.Service
    // Tasks are independent, cancelable goroutines having the lifetime of
    // the consumer, such as service loops and the like. Applications may
    // add additional tasks which should be started with the consumer.
    Tasks *task.Group
}