dnswatcher/internal/server/server_test.go

package server_test

import (
	"net"
	"strings"
	"testing"

	"github.com/spf13/viper"
	"go.uber.org/fx"

	"sneak.berlin/go/dnswatcher/internal/config"
	"sneak.berlin/go/dnswatcher/internal/globals"
	"sneak.berlin/go/dnswatcher/internal/handlers"
	"sneak.berlin/go/dnswatcher/internal/healthcheck"
	"sneak.berlin/go/dnswatcher/internal/logger"
	"sneak.berlin/go/dnswatcher/internal/middleware"
	"sneak.berlin/go/dnswatcher/internal/notify"
	"sneak.berlin/go/dnswatcher/internal/server"
	"sneak.berlin/go/dnswatcher/internal/state"
)

// newServerApp builds an fx app holding a *server.Server wired exactly
// as cmd/dnswatcher wires it, minus the watcher/resolver subtree that
// would touch live DNS, plus the given option. config.New reads viper,
// so the caller must first configure it, which is also why the caller
// cannot run in parallel.
func newServerApp(option fx.Option) *fx.App {
	return fx.New(
		fx.NopLogger,
		fx.Provide(
			globals.New,
			logger.New,
			config.New,
			state.New,
			healthcheck.New,
			notify.New,
			middleware.New,
			handlers.New,
			server.New,
		),
		option,
	)
}

// buildServer builds the server without starting the app's lifecycle,
// so no OnStart hook runs and nothing listens or resolves.
func buildServer(t *testing.T) *server.Server {
	t.Helper()

	var srv *server.Server

	app := newServerApp(fx.Populate(&srv))

	err := app.Err()
	if err != nil {
		t.Fatalf("building server graph: %v", err)
	}

	return srv
}

// TestRunWiresSocketTimeouts pins that the http.Server the running
// server actually serves — the one Run builds and serves on the port
// it binds — carries every socket-level timeout, plus the two
// relationships the values must satisfy.
//
// Run is given an unbindable port: it builds and stores s.httpServer,
// then the bind fails and Run returns the error without ever
// listening. Nothing here measures elapsed time.
//
// ReadTimeout must be at least ReadHeaderTimeout. net/http reads the
// headers under ReadHeaderTimeout, then sets the read deadline for the
// rest of the request to ReadTimeout, counted from when it started
// reading the request. If ReadTimeout were smaller, a request whose
// headers arrived after ReadTimeout but within ReadHeaderTimeout would
// get a read deadline that had already passed, so reading its body
// would fail at once.
func TestRunWiresSocketTimeouts(t *testing.T) {
	// Sets an env var and touches viper global state, so like the
	// config tests it cannot use t.Parallel.
	viper.Reset()
	t.Setenv("DNSWATCHER_TARGETS", "example.com")

	srv := buildServer(t)
	server.SetListenPort(srv, -1)

	err := srv.Run(t.Context())
	if err == nil {
		t.Fatal("Run bound port -1")
	}

	hs := server.HTTPServerOf(srv)
	if hs == nil {
		t.Fatal("Run did not build an http.Server")
	}

	if hs.ReadTimeout <= 0 {
		t.Errorf("ReadTimeout must be non-zero, got %v", hs.ReadTimeout)
	}

	if hs.ReadHeaderTimeout <= 0 {
		t.Errorf(
			"ReadHeaderTimeout must be non-zero, got %v",
			hs.ReadHeaderTimeout,
		)
	}

	if hs.WriteTimeout <= 0 {
		t.Errorf("WriteTimeout must be non-zero, got %v", hs.WriteTimeout)
	}

	if hs.IdleTimeout <= 0 {
		t.Errorf("IdleTimeout must be non-zero, got %v", hs.IdleTimeout)
	}

	if hs.WriteTimeout <= server.RequestTimeout {
		t.Errorf(
			"WriteTimeout (%v) must exceed handler budget (%v)",
			hs.WriteTimeout,
			server.RequestTimeout,
		)
	}

	if hs.ReadTimeout < hs.ReadHeaderTimeout {
		t.Errorf(
			"ReadTimeout (%v) must be >= ReadHeaderTimeout (%v)",
			hs.ReadTimeout,
			hs.ReadHeaderTimeout,
		)
	}

	if hs.Handler != srv {
		t.Errorf(
			"Run wired handler %T, want the *server.Server",
			hs.Handler,
		)
	}
}

func TestPortInUseStopsStartup(t *testing.T) {
	// Bound on every address, as Run binds, so that Run's bind fails.
	lc := &net.ListenConfig{}

	taken, err := lc.Listen(t.Context(), "tcp", ":0")
	if err != nil {
		t.Fatalf("binding a port for the test: %v", err)
	}

	defer func() { _ = taken.Close() }()

	_, port, err := net.SplitHostPort(taken.Addr().String())
	if err != nil {
		t.Fatalf("reading the bound port: %v", err)
	}

	viper.Reset()
	t.Setenv("DNSWATCHER_TARGETS", "example.com")
	t.Setenv("DNSWATCHER_DATA_DIR", t.TempDir())
	t.Setenv("PORT", port)

	app := newServerApp(fx.Invoke(func(*server.Server) {}))

	err = app.Start(t.Context())
	if err == nil {
		_ = app.Stop(t.Context())

		t.Fatal("startup succeeded on a port that is already bound")
	}

	if !strings.Contains(err.Error(), ":"+port) {
		t.Errorf("startup error does not name port %s: %v", port, err)
	}
}