initial commit

cache.go

@@ -0,0 +1,117 @@
+package commander
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"time"
+
+	"github.com/vmihailenco/msgpack/v5"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/codes"
+	"go.opentelemetry.io/otel/trace"
+)
+
+const cacheTTL = 5 * time.Second
+
+type Cache interface {
+	Set(key string, value []byte, ttl time.Duration) error
+	Get(key string) ([]byte, error)
+}
+
+type commandCache struct {
+	tracer trace.Tracer
+	cache  Cache
+	ttl    time.Duration
+
+	locks sync.Map
+}
+
+func newCommandCache(cache Cache, ttl time.Duration) *commandCache {
+	tracer := otel.Tracer(tracerName)
+
+	if ttl <= 0 {
+		ttl = cacheTTL
+	}
+
+	return &commandCache{
+		tracer: tracer,
+		cache:  cache,
+		ttl:    ttl,
+	}
+}
+
+func (c *commandCache) CommandCacheGet(ctx context.Context, key string, commands ...Command) bool {
+	ctx, span := c.tracer.Start(ctx, "command_cache.get")
+	defer span.End()
+
+	defer c.locker(ctx, key)()
+
+	res, err := c.cache.Get(key)
+	if err != nil {
+		span.RecordError(fmt.Errorf("cache get: %w", err))
+		span.SetStatus(codes.Error, err.Error())
+
+		return false
+	}
+
+	if len(res) == 0 {
+		span.AddEvent("cache miss")
+
+		return false
+	}
+
+	span.AddEvent("cache hit")
+
+	if err := c.unmarshal(res, commands); err != nil {
+		span.RecordError(fmt.Errorf("unmarshal commands: %w", err))
+		span.SetStatus(codes.Error, err.Error())
+
+		return false
+	}
+
+	return true
+}
+
+func (c *commandCache) CommandCacheStore(ctx context.Context, key string, commands ...Command) {
+	ctx, span := c.tracer.Start(ctx, "command_cache.store")
+	defer span.End()
+
+	defer c.locker(ctx, key)()
+
+	marshaled, err := c.marshal(commands)
+	if err != nil {
+		span.RecordError(fmt.Errorf("marshal commands: %w", err))
+		span.SetStatus(codes.Error, err.Error())
+
+		return
+	}
+
+	if err := c.cache.Set(key, marshaled, c.ttl); err != nil {
+		span.RecordError(fmt.Errorf("set cache: %w", err))
+		span.SetStatus(codes.Error, err.Error())
+	}
+}
+
+func (c *commandCache) locker(ctx context.Context, key string) (unlock func()) {
+	ctx, span := c.tracer.Start(ctx, "locker")
+	defer span.End()
+
+	for {
+		if _, loaded := c.locks.LoadOrStore(key, true); !loaded {
+			break
+		}
+	}
+
+	return func() {
+		c.locks.Delete(key)
+	}
+}
+
+func (c *commandCache) marshal(commands []Command) ([]byte, error) {
+	return msgpack.Marshal(commands)
+}
+
+func (c *commandCache) unmarshal(res []byte, commands []Command) error {
+	return msgpack.Unmarshal(res, &commands)
+}