dnswatcher/internal/server/sentry_test.go

package server_test

import (
	"io"
	"net/http"
	"net/http/httptest"
	"net/url"
	"strings"
	"sync"
	"testing"
	"time"

	"github.com/getsentry/sentry-go"
	"github.com/spf13/viper"
	"go.uber.org/fx"

	"sneak.berlin/go/dnswatcher/internal/server"
)

// The tests below set env vars and touch the global state of viper and
// of Sentry, so they cannot use t.Parallel.

// standInDelay is how long the Sentry stand-in takes to answer. It
// records a report only then, so a report that Shutdown did not wait
// for has not been recorded yet when Shutdown returns.
const standInDelay = 100 * time.Millisecond

// sentryStandIn is a local HTTP server in place of Sentry's, so that
// nothing a test reports leaves the host. It keeps the body of every
// request it receives.
type sentryStandIn struct {
	server *httptest.Server
	mu     sync.Mutex
	bodies []string
}

func newSentryStandIn(t *testing.T) *sentryStandIn {
	t.Helper()

	standIn := &sentryStandIn{}
	standIn.server = httptest.NewServer(http.HandlerFunc(
		func(_ http.ResponseWriter, r *http.Request) {
			body, err := io.ReadAll(r.Body)
			if err != nil {
				t.Errorf("reading request to the Sentry stand-in: %v", err)
			}

			time.Sleep(standInDelay)

			standIn.mu.Lock()
			defer standIn.mu.Unlock()

			standIn.bodies = append(standIn.bodies, string(body))
		},
	))
	t.Cleanup(standIn.server.Close)

	return standIn
}

// dsn returns a DSN that points Sentry at the stand-in.
func (s *sentryStandIn) dsn(t *testing.T) string {
	t.Helper()

	dsn, err := url.Parse(s.server.URL)
	if err != nil {
		t.Fatalf("parsing the stand-in URL: %v", err)
	}

	dsn.User = url.User("public-key")
	dsn.Path = "/1"

	return dsn.String()
}

// received reports whether a request to the stand-in contained text.
func (s *sentryStandIn) received(text string) bool {
	s.mu.Lock()
	defer s.mu.Unlock()

	for _, body := range s.bodies {
		if strings.Contains(body, text) {
			return true
		}
	}

	return false
}

func TestSentryUnsetDoesNothing(t *testing.T) {
	viper.Reset()
	t.Setenv("DNSWATCHER_TARGETS", "example.com")
	t.Setenv("DNSWATCHER_SENTRY_DSN", "")

	srv := buildServer(t)

	err := server.EnableSentry(srv)
	if err != nil {
		t.Fatalf("Sentry setup with no DSN: %v", err)
	}

	if sentry.CurrentHub().Client() != nil {
		t.Error("Sentry was set up with no DSN configured")
	}
}

// TestSentryReportsHandlerPanic checks that with a valid DSN a panic in
// a handler is reported to Sentry, still reaches chimw.Recoverer, and
// has been sent by the time Shutdown returns, and that nothing else is
// sent to Sentry.
func TestSentryReportsHandlerPanic(t *testing.T) {
	standIn := newSentryStandIn(t)

	viper.Reset()
	t.Setenv("DNSWATCHER_TARGETS", "example.com")
	t.Setenv("DNSWATCHER_SENTRY_DSN", standIn.dsn(t))

	srv := buildServer(t)

	err := server.EnableSentry(srv)
	if err != nil {
		t.Fatalf("Sentry setup with a valid DSN: %v", err)
	}

	// Sentry's client is global: close it so later tests find none.
	t.Cleanup(func() {
		sentry.CurrentHub().Client().Close()
		sentry.CurrentHub().BindClient(nil)
	})

	const panicMessage = "handler panic in the Sentry test"

	srv.SetupRoutes()
	server.RouterOf(srv).Get(
		"/panic",
		func(http.ResponseWriter, *http.Request) {
			panic(panicMessage)
		},
	)

	// An ordinary request first: with client reports on, Sentry would
	// add a count of its dropped transaction to the panic report.
	serve(srv, httptest.NewRequestWithContext(
		t.Context(), http.MethodGet, "/.well-known/healthcheck", nil,
	))

	rec := serve(srv, httptest.NewRequestWithContext(
		t.Context(), http.MethodGet, "/panic", nil,
	))
	if rec.Code != http.StatusInternalServerError {
		t.Errorf(
			"status %d, want %d from the recoverer",
			rec.Code, http.StatusInternalServerError,
		)
	}

	err = srv.Shutdown(t.Context())
	if err != nil {
		t.Fatalf("Shutdown: %v", err)
	}

	if !standIn.received(panicMessage) {
		t.Error("the panic had not been sent to Sentry when Shutdown returned")
	}

	if standIn.received("client_report") {
		t.Error("Sentry was sent a client report, not only the panic")
	}
}

func TestSentryInvalidDSNStopsStartup(t *testing.T) {
	viper.Reset()
	t.Setenv("DNSWATCHER_TARGETS", "example.com")
	t.Setenv("DNSWATCHER_DATA_DIR", t.TempDir())
	// Sentry cannot parse this: it has no public key before the host.
	t.Setenv("DNSWATCHER_SENTRY_DSN", "https://sentry.test/1")

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

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

		t.Fatal("startup succeeded with an invalid DSN")
	}

	if !strings.Contains(err.Error(), "invalid DNSWATCHER_SENTRY_DSN") {
		t.Errorf("startup error does not name the setting: %v", err)
	}
}