Seed from go-template-repo, renamed to simplexcalc

The template's files at a77fd30, without its history or LICENSE, after
script/rename simplexcalc.

Model: opus-5-5

internal/telemetry/sentry.go

@@ -0,0 +1,112 @@
+// Package telemetry owns error reporting (Sentry) and metrics
+// (Prometheus). Both are optional at runtime and neither is allowed to
+// take the process down: a monitoring backend that is unreachable must
+// not stop the service it monitors.
+package telemetry
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+	"time"
+
+	"github.com/getsentry/sentry-go"
+	"go.uber.org/fx"
+	"sneak.berlin/go/simplexcalc/internal/config"
+	"sneak.berlin/go/simplexcalc/internal/globals"
+	"sneak.berlin/go/simplexcalc/internal/logger"
+)
+
+// flushTimeout bounds how long shutdown waits for queued events to
+// reach Sentry. Exceeding it drops the tail rather than hanging the
+// stop sequence.
+const flushTimeout = 2 * time.Second
+
+// SentryParams defines dependencies for Sentry.
+type SentryParams struct {
+	fx.In
+
+	Config  *config.Config
+	Globals *globals.Globals
+	Logger  *logger.Logger
+}
+
+// Sentry wraps the client. When SENTRY_DSN is unset the wrapper still
+// exists and every method is a no-op, so no caller needs a nil check
+// and no caller behaves differently in development.
+type Sentry struct {
+	enabled bool
+	log     *slog.Logger
+}
+
+// NewSentry initialises the client if a DSN is configured. A DSN that
+// is present but malformed has already failed config parsing; a DSN the
+// client itself rejects is logged and reporting stays off, because a
+// telemetry backend is not a reason to refuse to serve.
+func NewSentry(lc fx.Lifecycle, params SentryParams) (*Sentry, error) {
+	s := &Sentry{log: params.Logger.Get()}
+
+	if params.Config.SentryDSN == "" {
+		s.log.Info("sentry disabled", "reason", "no DSN configured")
+
+		return s, nil
+	}
+
+	err := sentry.Init(sentry.ClientOptions{
+		Dsn:         params.Config.SentryDSN,
+		Environment: params.Config.SentryEnvironment,
+		Release:     params.Globals.Appname + "@" + params.Globals.Version,
+		// Panics are reported explicitly by the recovery middleware,
+		// which also has to answer the request; letting the SDK
+		// re-raise them would take the process down.
+		Debug: params.Config.Debug,
+	})
+	if err != nil {
+		s.log.Error("sentry init failed; error reporting is off", "error", err)
+
+		return s, nil
+	}
+
+	s.enabled = true
+
+	s.log.Info("sentry enabled", "environment", params.Config.SentryEnvironment)
+
+	lc.Append(fx.Hook{
+		OnStop: func(_ context.Context) error {
+			sentry.Flush(flushTimeout)
+
+			return nil
+		},
+	})
+
+	return s, nil
+}
+
+// Enabled reports whether events are actually being sent.
+func (s *Sentry) Enabled() bool {
+	return s.enabled
+}
+
+// CaptureError reports an error, and always logs it. Logging is not
+// conditional on Sentry being on: the log is the record of record, and
+// Sentry is a convenience on top of it.
+func (s *Sentry) CaptureError(err error) {
+	if err == nil {
+		return
+	}
+
+	s.log.Error("captured error", "error", err)
+
+	if s.enabled {
+		sentry.CaptureException(err)
+	}
+}
+
+// CapturePanic reports a recovered panic value with its stack.
+func (s *Sentry) CapturePanic(v any, stack []byte) {
+	s.log.Error("recovered panic", "panic", fmt.Sprint(v), "stack", string(stack))
+
+	if s.enabled {
+		sentry.CurrentHub().Recover(v)
+	}
+}