feat: cache revalidation

internal/filesystem/read.go

@@ -0,0 +1,109 @@
+package filesystem
+
+import (
+	"context"
+	"encoding/json"
+	"log/slog"
+	"strings"
+	"time"
+
+	"github.com/valkey-io/valkey-go"
+)
+
+const keyRead = "webdav:read:"
+
+type readFile struct {
+	Age     time.Time `json:"age"`
+	Content []byte    `json:"content"`
+}
+
+func (c *CachedClient) Read(path string) ([]byte, error) {
+	key := keyRead + path
+	ctx := context.Background()
+
+	// Try cache
+	cached, err := c.client.Do(ctx, c.client.B().Get().Key(key).Build()).AsBytes()
+	if err == nil && len(cached) > 0 {
+		c.readHits.Add(1)
+		c.hits.Add(1)
+		slog.Debug("cache hit", "key", key)
+
+		var file readFile
+		err := json.Unmarshal(cached, &file)
+		if err != nil {
+			slog.Error("could not Unmarshal cache", "key", key, "err", err)
+		} else {
+			return file.Content, nil
+		}
+
+	}
+
+	// Cache miss
+	c.misses.Add(1)
+	slog.Debug("cache miss", "key", key)
+
+	data, err := c.impl.Read(path)
+	if err != nil {
+		return nil, err
+	}
+	file := readFile{
+		Age:     time.Now(),
+		Content: data,
+	}
+
+	cached, err = json.Marshal(file)
+	if err != nil {
+		slog.Error("could not marshal file for cache", "key", key, "err", err)
+		return data, nil
+	}
+
+	// Cache
+	c.client.Do(ctx, c.client.B().Set().Key(key).Value(valkey.BinaryString(cached)).Ex(c.ttl).Build())
+
+	return data, nil
+}
+
+func (c *CachedClient) revalidateRead(ctx context.Context) {
+	startTime := time.Now()
+	c.scanAndProcess(ctx, keyRead+"*", func(key string) error {
+		path := strings.TrimPrefix(key, keyRead)
+		cached, err := c.client.Do(ctx, c.client.B().Get().Key(key).Build()).AsBytes()
+		if err != nil {
+			// Key might be gone or error fetching
+			return nil
+		}
+
+		var cachedFile readFile
+		err = json.Unmarshal(cached, &cachedFile)
+		if err != nil {
+			c.client.Do(ctx, c.client.B().Del().Key(key).Build())
+			return err
+		}
+
+		info, err := c.impl.Stat(path)
+		if err != nil {
+			c.client.Do(ctx, c.client.B().Del().Key(key).Build())
+			return nil
+		}
+
+		if info.ModTime().After(cachedFile.Age) {
+			data, err := c.impl.Read(path)
+			if err != nil {
+				return err
+			}
+			cachedFile.Age = time.Now()
+			cachedFile.Content = data
+
+			newCached, err := json.Marshal(cachedFile)
+			if err != nil {
+				return err
+			}
+
+			c.client.Do(ctx, c.client.B().Set().Key(key).Value(valkey.BinaryString(newCached)).Ex(c.ttl).Build())
+		} else {
+			c.client.Do(ctx, c.client.B().Expire().Key(key).Seconds(int64(c.ttl/time.Second)).Build())
+		}
+		return nil
+	})
+	slog.Debug("revalidation of read complete", "duration", time.Since(startTime))
+}