Write device aliases as startup metadata

internal/pipeline/service.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"log/slog"
 	"regexp"
+	"sort"
 	"strings"
 	"sync/atomic"
 	"time"
@@ -22,6 +23,7 @@ type writer interface {
 type Service struct {
 	config        config.Config
 	deviceAliases map[string]string
+	aliasRecords  []model.Record
 	influxClient  writer
 	input         chan model.RawMessage
 	received      atomic.Uint64
@@ -40,9 +42,11 @@ type Snapshot struct {
 }
 
 func NewService(cfg config.Config, influxClient writer) *Service {
+	normalizedAliases := normalizeDeviceAliases(cfg.DeviceAliases)
 	return &Service{
 		config:        cfg,
-		deviceAliases: normalizeDeviceAliases(cfg.DeviceAliases),
+		deviceAliases: normalizedAliases,
+		aliasRecords:  buildAliasRecords(normalizedAliases),
 		influxClient:  influxClient,
 		input:         make(chan model.RawMessage, cfg.App.BufferSize),
 	}
@@ -63,7 +67,18 @@ func (service *Service) Run(ctx context.Context) error {
 	ticker := time.NewTicker(service.config.App.FlushInterval.Duration)
 	defer ticker.Stop()
 
-	batch := make([]model.Record, 0, service.config.App.BatchSize)
+	batch := append(make([]model.Record, 0, service.config.App.BatchSize+len(service.aliasRecords)), service.aliasRecords...)
+	if len(batch) > 0 {
+		flushCtx, cancel := context.WithTimeout(ctx, service.config.App.FlushTimeout.Duration)
+		err := service.flush(flushCtx, batch)
+		cancel()
+		if err != nil {
+			slog.Error("failed to flush alias metadata to influx; will retry on next interval", "count", len(batch), "error", err)
+		} else {
+			batch = batch[:0]
+		}
+	}
+
 	var input <-chan model.RawMessage = service.input
 
 	for {
@@ -204,3 +219,33 @@ func normalizeDeviceKey(value string) string {
 	normalized = strings.Trim(normalized, "_")
 	return normalized
 }
+
+func buildAliasRecords(aliases map[string]string) []model.Record {
+	if len(aliases) == 0 {
+		return nil
+	}
+
+	devices := make([]string, 0, len(aliases))
+	for device := range aliases {
+		devices = append(devices, device)
+	}
+	sort.Strings(devices)
+
+	timestamp := time.Now().UTC()
+	records := make([]model.Record, 0, len(devices))
+	for _, device := range devices {
+		records = append(records, model.Record{
+			Measurement: "tasmota_device_meta",
+			Tags: map[string]string{
+				"device": device,
+				"source": "config",
+			},
+			Fields: map[string]any{
+				"device_alias": aliases[device],
+			},
+			Timestamp: timestamp,
+		})
+	}
+
+	return records
+}

internal/pipeline/service_test.go

@@ -43,6 +43,18 @@ func (writer *fakeWriter) firstBatch() []model.Record {
 	return writer.batches[0]
 }
 
+func (writer *fakeWriter) allBatches() [][]model.Record {
+	writer.mu.Lock()
+	defer writer.mu.Unlock()
+
+	copyBatches := make([][]model.Record, 0, len(writer.batches))
+	for _, batch := range writer.batches {
+		copyBatches = append(copyBatches, append([]model.Record(nil), batch...))
+	}
+
+	return copyBatches
+}
+
 func TestServiceFlushesParsedRecords(t *testing.T) {
 	fake := newFakeWriter()
 	service := NewService(config.Config{
@@ -66,6 +78,12 @@ func TestServiceFlushesParsedRecords(t *testing.T) {
 		errCh <- service.Run(ctx)
 	}()
 
+	select {
+	case <-fake.flushed:
+	case <-time.After(2 * time.Second):
+		t.Fatal("timed out waiting for alias metadata flush")
+	}
+
 	service.Enqueue(model.RawMessage{
 		Topic:      "tele/tasmota_896001/LWT",
 		Payload:    []byte("Online"),
@@ -83,7 +101,23 @@ func TestServiceFlushesParsedRecords(t *testing.T) {
 		t.Fatal("timed out waiting for pipeline flush")
 	}
 
-	batch := fake.firstBatch()
+	batches := fake.allBatches()
+	if len(batches) != 2 {
+		t.Fatalf("expected 2 flushed batches, got %d", len(batches))
+	}
+
+	metaBatch := batches[0]
+	if len(metaBatch) != 2 {
+		t.Fatalf("expected 2 alias metadata records, got %d", len(metaBatch))
+	}
+	if metaBatch[0].Measurement != "tasmota_device_meta" {
+		t.Fatalf("unexpected metadata measurement: %s", metaBatch[0].Measurement)
+	}
+	if metaBatch[0].Fields["device_alias"] == "" {
+		t.Fatalf("expected metadata batch to include device_alias, got %#v", metaBatch[0].Fields["device_alias"])
+	}
+
+	batch := batches[1]
 	if len(batch) != 2 {
 		t.Fatalf("expected 2 records in flushed batch, got %d", len(batch))
 	}