[chore] prometheusremotewrite: simplify wal initialization

Signed-off-by: Bogdan Drutu <bogdandrutu@gmail.com>

exporter/prometheusremotewriteexporter/exporter.go

@@ -80,14 +80,8 @@ func newPRWExporter(cfg *Config, set exporter.CreateSettings) (*prwExporter, err
 			SendMetadata:        cfg.SendMetadata,
 		},
 	}
-	if cfg.WAL == nil {
-		return prwe, nil
-	}
 
-	prwe.wal, err = newWAL(cfg.WAL, prwe.export)
-	if err != nil {
-		return nil, err
-	}
+	prwe.wal = newWAL(cfg.WAL, prwe.export)
 	return prwe, nil
 }
 

exporter/prometheusremotewriteexporter/wal.go

@@ -59,11 +59,11 @@ func (wc *WALConfig) truncateFrequency() time.Duration {
 	return defaultWALTruncateFrequency
 }
 
-func newWAL(walConfig *WALConfig, exportSink func(context.Context, []*prompb.WriteRequest) error) (*prweWAL, error) {
+func newWAL(walConfig *WALConfig, exportSink func(context.Context, []*prompb.WriteRequest) error) *prweWAL {
 	if walConfig == nil {
 		// There are cases for which the WAL can be disabled.
 		// TODO: Perhaps log that the WAL wasn't enabled.
-		return nil, errNilConfig
+		return nil
 	}
 
 	return &prweWAL{
@@ -72,7 +72,7 @@ func newWAL(walConfig *WALConfig, exportSink func(context.Context, []*prompb.Wri
 		stopChan:   make(chan struct{}),
 		rWALIndex:  &atomic.Uint64{},
 		wWALIndex:  &atomic.Uint64{},
-	}, nil
+	}
 }
 
 func (wc *WALConfig) createWAL() (*wal.Log, string, error) {
@@ -90,7 +90,6 @@ func (wc *WALConfig) createWAL() (*wal.Log, string, error) {
 var (
 	errAlreadyClosed = errors.New("already closed")
 	errNilWAL        = errors.New("wal is nil")
-	errNilConfig     = errors.New("expecting a non-nil configuration")
 )
 
 // retrieveWALIndices queries the WriteAheadLog for its current first and last indices.

exporter/prometheusremotewriteexporter/wal_test.go

@@ -21,16 +21,14 @@ func doNothingExportSink(_ context.Context, reqL []*prompb.WriteRequest) error {
 
 func TestWALCreation_nilConfig(t *testing.T) {
 	config := (*WALConfig)(nil)
-	pwal, err := newWAL(config, doNothingExportSink)
-	require.Equal(t, err, errNilConfig)
+	pwal := newWAL(config, doNothingExportSink)
 	require.Nil(t, pwal)
 }
 
 func TestWALCreation_nonNilConfig(t *testing.T) {
 	config := &WALConfig{Directory: t.TempDir()}
-	pwal, err := newWAL(config, doNothingExportSink)
+	pwal := newWAL(config, doNothingExportSink)
 	require.NotNil(t, pwal)
-	assert.Nil(t, err)
 	assert.NoError(t, pwal.stop())
 }
 
@@ -80,27 +78,24 @@ func TestWALStopManyTimes(t *testing.T) {
 		TruncateFrequency: 60 * time.Microsecond,
 		BufferSize:        1,
 	}
-	pwal, err := newWAL(config, doNothingExportSink)
-	require.Nil(t, err)
+	pwal := newWAL(config, doNothingExportSink)
 	require.NotNil(t, pwal)
 
 	// Ensure that invoking .stop() multiple times doesn't cause a panic, but actually
 	// First close should NOT return an error.
-	err = pwal.stop()
-	require.Nil(t, err)
+	require.NoError(t, pwal.stop())
 	for i := 0; i < 4; i++ {
 		// Every invocation to .stop() should return an errAlreadyClosed.
-		err = pwal.stop()
-		require.Equal(t, err, errAlreadyClosed)
+		require.ErrorIs(t, pwal.stop(), errAlreadyClosed)
 	}
 }
 
 func TestWAL_persist(t *testing.T) {
 	// Unit tests that requests written to the WAL persist.
 	config := &WALConfig{Directory: t.TempDir()}
 
-	pwal, err := newWAL(config, doNothingExportSink)
-	require.Nil(t, err)
+	pwal := newWAL(config, doNothingExportSink)
+	require.NotNil(t, pwal)
 
 	// 1. Write out all the entries.
 	reqL := []*prompb.WriteRequest{
@@ -127,27 +122,25 @@ func TestWAL_persist(t *testing.T) {
 	}
 
 	ctx := context.Background()
-	err = pwal.retrieveWALIndices()
-	require.Nil(t, err)
+	require.NoError(t, pwal.retrieveWALIndices())
 	t.Cleanup(func() {
 		assert.NoError(t, pwal.stop())
 	})
 
-	err = pwal.persistToWAL(reqL)
-	require.Nil(t, err)
+	require.NoError(t, pwal.persistToWAL(reqL))
 
 	// 2. Read all the entries from the WAL itself, guided by the indices available,
 	// and ensure that they are exactly in order as we'd expect them.
 	wal := pwal.wal
 	start, err := wal.FirstIndex()
-	require.Nil(t, err)
+	require.NoError(t, err)
 	end, err := wal.LastIndex()
-	require.Nil(t, err)
+	require.NoError(t, err)
 
 	var reqLFromWAL []*prompb.WriteRequest
 	for i := start; i <= end; i++ {
 		req, err := pwal.readPrompbFromWAL(ctx, i)
-		require.Nil(t, err)
+		require.NoError(t, err)
 		reqLFromWAL = append(reqLFromWAL, req)
 	}