refactor state to recorder, finish implementing

pkg/weather/recorder/recorder.go

@@ -0,0 +1,42 @@
+package recorder
+
+import (
+	"context"
+	"sync"
+
+	"go.opentelemetry.io/otel/metric"
+	"go.opentelemetry.io/otel/trace"
+
+	"gitea.libretechconsulting.com/rmcguire/go-app/pkg/otel"
+
+	"gitea.libretechconsulting.com/rmcguire/ambient-local-exporter/pkg/weather"
+)
+
+type WeatherRecorder struct {
+	updates []*weather.WeatherUpdate
+	keep    int
+	ctx     context.Context
+	tracer  trace.Tracer
+	meter   metric.Meter
+	*sync.RWMutex
+}
+
+type Opts struct {
+	Ctx      context.Context
+	KeepLast int
+}
+
+func NewWeatherRecorder(opts *Opts) *WeatherRecorder {
+	if opts.KeepLast < 1 {
+		opts.KeepLast = 1
+	}
+
+	return &WeatherRecorder{
+		updates: make([]*weather.WeatherUpdate, 0, opts.KeepLast),
+		keep:    opts.KeepLast,
+		ctx:     opts.Ctx,
+		tracer:  otel.GetTracer(opts.Ctx, "weatherRecorder"),
+		meter:   otel.GetMeter(opts.Ctx, "weatherRecorder"),
+		RWMutex: &sync.RWMutex{},
+	}
+}

pkg/weather/recorder/recorder_get.go

@@ -0,0 +1,90 @@
+package recorder
+
+import (
+	"context"
+	"errors"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/trace"
+
+	"gitea.libretechconsulting.com/rmcguire/ambient-local-exporter/pkg/weather"
+)
+
+// Returns last requested number of weather updates
+// If negative number given, will return all weather observations
+func (w *WeatherRecorder) Get(ctx context.Context, last int) (
+	[]*weather.WeatherUpdate, error,
+) {
+	if last < 0 {
+		last = w.keep
+	} else if last < 1 {
+		last = 1
+	}
+
+	ctx, span := w.tracer.Start(ctx, "getWeatherRecorder")
+	span.SetAttributes(
+		attribute.Int("last", last),
+		attribute.Int("keep", w.keep),
+		attribute.Int("currentSize", w.Count()),
+	)
+	defer span.End()
+
+	updates, err := w.get(ctx, last)
+	if err != nil {
+		span.RecordError(err)
+		span.SetStatus(codes.Error, err.Error())
+	} else {
+		span.SetStatus(codes.Ok, "")
+	}
+
+	return updates, err
+}
+
+func (w *WeatherRecorder) get(ctx context.Context, last int) (
+	[]*weather.WeatherUpdate, error,
+) {
+	span := trace.SpanFromContext(ctx)
+
+	w.RLock()
+	defer w.Unlock()
+
+	span.AddEvent("acquired lock on recorder cache")
+
+	updates := w.updates
+
+	if w.count() == 0 {
+		err := errors.New("no recorded updates to get")
+		span.RecordError(err)
+		return nil, err
+	} else if w.count() <= last {
+		span.RecordError(errors.New("requested more updates than recorded"))
+	} else {
+		updates = updates[len(updates)-last:]
+	}
+
+	span.SetAttributes(attribute.Int("retrieved", len(updates)))
+	span.SetStatus(codes.Ok, "")
+
+	return updates, nil
+}
+
+// Returns count of retained weather updates
+func (w *WeatherRecorder) Count() int {
+	_, span := w.tracer.Start(w.ctx, "countWeatherRecorder")
+	defer span.End()
+
+	count := w.count()
+
+	span.SetAttributes(attribute.Int("count", count))
+	span.SetStatus(codes.Ok, "")
+
+	return count
+}
+
+func (w *WeatherRecorder) count() int {
+	w.RLock()
+	defer w.RUnlock()
+
+	return len(w.updates)
+}

pkg/weather/recorder/recorder_set.go

@@ -0,0 +1,35 @@
+package recorder
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/trace"
+
+	"gitea.libretechconsulting.com/rmcguire/ambient-local-exporter/pkg/weather"
+)
+
+func (w *WeatherRecorder) Set(ctx context.Context, u *weather.WeatherUpdate) error {
+	_, span := w.tracer.Start(ctx, "recordWeatherUpdate")
+	span.SetAttributes(
+		attribute.Int("countWeatherUpdates", w.Count()),
+		attribute.Int("keepUpdates", w.keep),
+	)
+	defer span.End()
+
+	return w.set(span, u)
+}
+
+func (w *WeatherRecorder) set(span trace.Span, u *weather.WeatherUpdate) error {
+	w.Lock()
+	defer w.Unlock()
+
+	if len(w.updates) > w.keep {
+		w.updates = w.updates[1:]
+		span.AddEvent("trimmed recorded updates by 1")
+	}
+
+	w.updates = append(w.updates, u)
+	span.AddEvent("recorded weather update")
+	return nil
+}