Move the archive files into their own package (closes #541)

The SQLite archive files the database target writes are now managed by
internal/archive: file names, rotation, the writer of each target,
pruning, renames, the gzipped JSON export, the idle sweep, and the
lock renames run under, which was Handlers.renameMu. The database
target stays in internal/delivery and writes through archive.Writers;
the engine still closes the writers when it stops, so the stop order
is unchanged. The handlers take the lock, rename and evict through
archive.Archives.

Exported names drop their Archive prefix in the new package. The
tests moved with the code; the two that check a delivery's recorded
attempt stay in delivery.

Model: opus-5-5

internal/delivery/export_test.go

@@ -12,16 +12,11 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"go.uber.org/fx"
 	"gorm.io/gorm"
+	"sneak.berlin/go/webhooker/internal/archive"
 	"sneak.berlin/go/webhooker/internal/database"
 	"sneak.berlin/go/webhooker/internal/metrics"
 )
 
-// ErrExportArchiveWriterEvicted exposes the sentinel returned by
-// an evicted archive writer. It carries the Err prefix rather
-// than this file's usual Export one because it is a sentinel
-// error.
-var ErrExportArchiveWriterEvicted = errArchiveWriterEvicted
-
 // Exported constants for test access.
 const (
 	ExportDeliveryChannelSize     = deliveryChannelSize
@@ -399,7 +394,8 @@ func (e *Engine) ExportRetryCh() chan Task {
 }
 
 // NewTestEngine creates an Engine for unit tests without
-// database dependencies.
+// database dependencies. Its archive writers have no data
+// directory, so a delivery to a database target fails.
 func NewTestEngine(
 	log *slog.Logger,
 	client *http.Client,
@@ -411,6 +407,7 @@ func NewTestEngine(
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    workers,
 		mtr:        metrics.New(prometheus.NewRegistry()),
+		archives:   archive.NewWriters(archive.WritersParams{Logger: log}),
 	}
 	e.initTargets(client)
 
@@ -423,9 +420,10 @@ func NewTestEngineSmallRetry(
 	log *slog.Logger,
 ) *Engine {
 	e := &Engine{
-		log:     log,
-		retryCh: make(chan Task, 1),
-		mtr:     metrics.New(prometheus.NewRegistry()),
+		log:      log,
+		retryCh:  make(chan Task, 1),
+		mtr:      metrics.New(prometheus.NewRegistry()),
+		archives: archive.NewWriters(archive.WritersParams{Logger: log}),
 	}
 	e.initTargets(nil)
 
@@ -433,7 +431,8 @@ func NewTestEngineSmallRetry(
 }
 
 // NewTestEngineWithDB creates an Engine with a real
-// database and dbManager for integration tests.
+// database and dbManager for integration tests, and archive
+// writers of its own over the same two.
 func NewTestEngineWithDB(
 	db *database.Database,
 	dbMgr *database.WebhookDBManager,
@@ -449,12 +448,22 @@ func NewTestEngineWithDB(
 		retryCh:    make(chan Task, retryChannelSize),
 		workers:    workers,
 		mtr:        metrics.New(prometheus.NewRegistry()),
+		archives: archive.NewWriters(archive.WritersParams{
+			Database:  db,
+			DBManager: dbMgr,
+			Logger:    log,
+		}),
 	}
 	e.initTargets(client)
 
 	return e
 }
 
+// ExportArchives returns the engine's archive writers.
+func (e *Engine) ExportArchives() *archive.Writers {
+	return e.archives
+}
+
 // ExportSetMetrics substitutes the engine's metric set, so a test can
 // assert on collectors registered on a registry it holds.
 func (e *Engine) ExportSetMetrics(mtr *metrics.Set) {
@@ -477,273 +486,3 @@ func NewTestCircuitBreaker(
 		cooldown:  cooldown,
 	}
 }
-
-// ExportArchivedEvent aliases the archive row type so black-box
-// tests can construct and read archive rows.
-type ExportArchivedEvent = archivedEvent
-
-// ExportArchiveWriter wraps an archiveWriter so black-box tests
-// can exercise the archive file mechanics.
-type ExportArchiveWriter struct {
-	w *archiveWriter
-}
-
-// NewExportArchiveWriter builds an archive writer for tests,
-// optionally overriding the reopen debounce (a non-positive
-// debounce keeps the production default).
-func NewExportArchiveWriter(
-	path string, log *slog.Logger, debounce time.Duration,
-) *ExportArchiveWriter {
-	w := newArchiveWriter(path, log)
-	if debounce > 0 {
-		w.debounce = debounce
-	}
-
-	return &ExportArchiveWriter{w: w}
-}
-
-// Write archives a row through the writer, into the file named
-// without a period.
-func (e *ExportArchiveWriter) Write(
-	row ExportArchivedEvent, expiry time.Duration,
-) error {
-	return e.w.write(row, expiry, "")
-}
-
-// WritePeriod archives a row through the writer, into the file for
-// period.
-func (e *ExportArchiveWriter) WritePeriod(
-	row ExportArchivedEvent, expiry time.Duration, period string,
-) error {
-	return e.w.write(row, expiry, period)
-}
-
-// Open opens the archive file, pruning when expiry is positive.
-func (e *ExportArchiveWriter) Open(expiry time.Duration) error {
-	return e.w.open(e.w.path, expiry)
-}
-
-// Reopen closes and reopens the archive file.
-func (e *ExportArchiveWriter) Reopen(
-	expiry time.Duration,
-) error {
-	return e.w.reopen(e.w.path, expiry)
-}
-
-// SetNow replaces the clock the writer measures its reopen
-// debounce on.
-func (e *ExportArchiveWriter) SetNow(now func() time.Time) {
-	e.w.now = now
-}
-
-// Reopens reports how many times the file has been opened.
-func (e *ExportArchiveWriter) Reopens() int {
-	return e.w.reopens
-}
-
-// DB returns the writer's current open handle for row
-// inspection in tests.
-func (e *ExportArchiveWriter) DB() *gorm.DB {
-	return e.w.db
-}
-
-// Path returns the archive file the writer owns.
-func (e *ExportArchiveWriter) Path() string {
-	return e.w.path
-}
-
-// OpenExisting opens the archive without permitting creation,
-// the way the idle sweep does.
-func (e *ExportArchiveWriter) OpenExisting(
-	expiry time.Duration,
-) error {
-	return e.w.openMode(e.w.path, archiveModeExisting, expiry)
-}
-
-// SweepExpired runs an idle sweep of the archive.
-func (e *ExportArchiveWriter) SweepExpired(
-	expiry time.Duration,
-) error {
-	return e.w.sweepExpired(expiry)
-}
-
-// Evict marks the writer evicted and closes its handle, exactly
-// as leaving the registry does.
-func (e *ExportArchiveWriter) Evict() {
-	e.w.evict()
-}
-
-// Rename gives the archive file a new name in the same directory,
-// as a rename of the webhook or target does.
-func (e *ExportArchiveWriter) Rename(name string) error {
-	return e.w.rename(name)
-}
-
-// HandleOpen reports whether the writer currently holds an open
-// archive handle.
-func (e *ExportArchiveWriter) HandleOpen() bool {
-	e.w.mu.Lock()
-	defer e.w.mu.Unlock()
-
-	return e.w.db != nil
-}
-
-// Same reports whether both wrappers refer to the very same
-// underlying archive writer, so a test can prove a registry entry
-// is the writer it was handed rather than a replacement.
-func (e *ExportArchiveWriter) Same(
-	other *ExportArchiveWriter,
-) bool {
-	return other != nil && e.w == other.w
-}
-
-// ExportArchiveWriterFor returns the archive writer the registry
-// currently caches for a database target, or nil when none is
-// cached. It never creates one, so a test can hold a reference to
-// the very writer an eviction is about to detach.
-func (e *Engine) ExportArchiveWriterFor(
-	targetID string,
-) *ExportArchiveWriter {
-	e.dbTarget.mu.Lock()
-	defer e.dbTarget.mu.Unlock()
-
-	w, ok := e.dbTarget.writers[targetID]
-	if !ok {
-		return nil
-	}
-
-	return &ExportArchiveWriter{w: w}
-}
-
-// ExportHasArchiveWriter reports whether the database target
-// type currently caches an archive writer for a target.
-func (e *Engine) ExportHasArchiveWriter(
-	targetID string,
-) bool {
-	e.dbTarget.mu.Lock()
-	defer e.dbTarget.mu.Unlock()
-
-	_, ok := e.dbTarget.writers[targetID]
-
-	return ok
-}
-
-// ExportArchiveHandleOpen reports whether the cached archive
-// writer for a target holds an open database handle. It
-// returns false when no writer is cached.
-func (e *Engine) ExportArchiveHandleOpen(
-	targetID string,
-) bool {
-	e.dbTarget.mu.Lock()
-	w, ok := e.dbTarget.writers[targetID]
-	e.dbTarget.mu.Unlock()
-
-	if !ok {
-		return false
-	}
-
-	w.mu.Lock()
-	defer w.mu.Unlock()
-
-	return w.db != nil
-}
-
-// ExportEnsureArchiveWriter creates (if needed) and returns the
-// archive file path of the cached writer for a target, so a
-// test can prime the registry the way a delivery would.
-func (e *Engine) ExportEnsureArchiveWriter(
-	targetID string,
-) (string, error) {
-	w, err := e.dbTarget.writerFor(targetID)
-	if err != nil {
-		return "", err
-	}
-
-	return w.path, nil
-}
-
-// ExportSweepWriterFor takes a target's registry writer exactly
-// as the idle sweep does, reporting whether the sweep had to
-// create the entry. It lets a test drive the registry through the
-// sweep's own entry point instead of choreographing goroutines.
-func (e *Engine) ExportSweepWriterFor(
-	targetID string,
-) (*ExportArchiveWriter, bool, error) {
-	w, created, err := e.dbTarget.sweepWriterFor(targetID)
-	if err != nil {
-		return nil, false, err
-	}
-
-	return &ExportArchiveWriter{w: w}, created, nil
-}
-
-// ExportReleaseSweepWriter releases a sweep-created registry entry
-// exactly as a finished sweep does.
-func (e *Engine) ExportReleaseSweepWriter(
-	targetID string, w *ExportArchiveWriter,
-) {
-	e.dbTarget.releaseSweepWriter(targetID, w.w)
-}
-
-// NewTestArchiveSweeper builds an ArchiveSweeper backed by the
-// given main database and engine, without the fx lifecycle.
-// Intended for tests.
-func NewTestArchiveSweeper(
-	db *database.Database,
-	eng *Engine,
-	log *slog.Logger,
-) *ArchiveSweeper {
-	return &ArchiveSweeper{
-		db:       db,
-		eng:      eng,
-		log:      log,
-		interval: time.Hour,
-	}
-}
-
-// ExportSweep runs a single archive sweep synchronously for
-// tests.
-func (s *ArchiveSweeper) ExportSweep(ctx context.Context) {
-	s.sweep(ctx)
-}
-
-// ExportStart starts the sweeper's background loop for tests.
-func (s *ArchiveSweeper) ExportStart() {
-	s.start()
-}
-
-// ExportRegisterHooks registers the sweeper's real fx lifecycle
-// hooks on a lifecycle supplied by a test, so a test can drive
-// the exact OnStart/OnStop functions the application runs and
-// hand OnStart the kind of context fx actually supplies.
-func (s *ArchiveSweeper) ExportRegisterHooks(lc fx.Lifecycle) {
-	s.registerHooks(lc)
-}
-
-// ExportStop stops the sweeper's background loop for tests.
-func (s *ArchiveSweeper) ExportStop(ctx context.Context) error {
-	return s.stop(ctx)
-}
-
-// ExportWedgeLoop adds a goroutine to the sweeper's WaitGroup
-// that never observes cancellation and returns only when release
-// is closed. It stands in for a prune stuck on a locked archive.
-func (s *ArchiveSweeper) ExportWedgeLoop(
-	release <-chan struct{},
-) {
-	s.wg.Go(func() {
-		<-release
-	})
-}
-
-// ExportSetInterval overrides the sweep interval for tests.
-func (s *ArchiveSweeper) ExportSetInterval(d time.Duration) {
-	s.interval = d
-}
-
-// ExportParseArchiveExpiry exposes parseArchiveExpiry.
-func ExportParseArchiveExpiry(
-	configJSON string,
-) (time.Duration, error) {
-	return parseArchiveExpiry(configJSON)
-}