marp	theme	_class	title
true	gaia	invert	go flexible

A collection of packages for building Go services.

---

Goals

• Provide flexible primitives to build upon.
• Simplify process lifecycle and graceful shutdown.
• No third party dependencies allowed within flex itself.
• All published packages must be tested.

---

Primitive: Runner

A Runner represents anything which can "run" itself. For example, an HTTP server.

// Runner represents the behaviour for running a service worker.
type Runner interface {
        // Run should run start processing the worker and be a blocking operation.
        Run(context.Context) error
}

---

Primitive: Halter

A Halter represents anything which can "halt" itself. For example a Kafka broker.

// Halter represents the behaviour for stopping a service worker.
type Halter interface {
        // Halt should tell the worker to stop doing work.
        Halt(context.Context) error
}

---

Primitive: Worker

A Worker represents anything that can both "run" and "halt" itself. For example, a cron job.

// Worker represents the behaviour for a service worker.
type Worker interface {
        Runner
        Halter
}

---

In Practice

---

Optics

• Consider io.Reader and io.Writer.
• Both single method interfaces.
• Both result in incredibly varried uses.

The goal of flex is to provide a similar experience, for building k8s native applications.

---

The flexhttp plugin

type Server struct{ *http.Server }

func NewHTTPServer(s *http.Server) *Server {
        return &Server{Server: s}
}
func (s *Server) Run(_ context.Context) error {
        log.Printf("serving on: http://localhost%s\n", s.Addr)
        return s.ListenAndServe()
}
func (s *Server) Halt(ctx context.Context) error {
        return s.Shutdown(ctx)
}

---

The flexmetrics plugin

flexmetrics exposes prometheus and pprof metrics on an http server. It's Worker is implemented by the concrete Server type.

type Server struct {
        Path   string
        Server *http.Server
}

---

Simple yet complete

// Run will start the metrics server.
func (s *Server) Run(_ context.Context) error {
        /* abbreviated... */
        mux := http.NewServeMux()
        mux.Handle(s.Path, promhttp.Handler())
        mux.HandleFunc("/debug/pprof/", pprof.Index)
        mux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
        mux.HandleFunc("/debug/pprof/profile", pprof.Profile)
        mux.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
        mux.HandleFunc("/debug/pprof/trace", pprof.Trace)
        /* abbreviated... */
}

---

More than meets the eye

• Environment variables for configuration
• Configurable port-bindings
• Configurable http server
• Sane defaults if you choose to use them

---

Live demo

Goals

• Build a non-trivial order system (think e-commerce).
• Demonstrate how flex eliminates a lot of complicated setup.
• Provide working example usecases for future reference.