chore: cosmetic fixes

TODO.md

@@ -6,20 +6,6 @@ barrel.Open(dir="/data/barrel")
 
 Create a `barrel.db` file inside `/data/barrel` which is the working data directory.
 
-- timer.Timer -> check if file needs to be rotated (5MB)
-- rename current active file
-- create new file
-
-- timer.Timer -> merge all these files 30 minutes
-- loop over all inactive files
-- delete records not required
-
-
-.Put("hello") -> "world"
-
-.Put("hello) -> "bye"
-
-
 ### Writing
 
 - [x] Encode the header
@@ -38,12 +24,16 @@ Create a `barrel.db` file inside `/data/barrel` which is the working data direct
 ### Background
 
 - [ ] Merge old files
-- [ ] Hints file
-- [ ] GC cleanup of old/expired/deleted keys
-
+- [x] Hints file
+- [x] GC cleanup of old/expired/deleted keys
+- [ ] Compaction routine
+- [ ] Rotate file if size increases
 ### Starting program
 
 - [ ] Load data from hints file for faster boot time
+
+### Misc
+
 - [ ] Create specific mutex for different things
 
 ## Test Cases

cmd/server/main.go

@@ -42,7 +42,7 @@ func main() {
 	mux.HandleFunc("get", app.get)
 	mux.HandleFunc("del", app.delete)
 
-	err = redcon.ListenAndServe(addr,
+	if err := redcon.ListenAndServe(addr,
 		mux.ServeRESP,
 		func(conn redcon.Conn) bool {
 			// use this function to accept or deny the connection.
@@ -51,9 +51,7 @@ func main() {
 		func(conn redcon.Conn, err error) {
 			// this is called when the connection has been closed
 		},
-	)
-	if err != nil {
+	); err != nil {
 		lo.Fatal("error starting server: %w", err)
 	}
-
 }

internal/datafile/datafile.go

@@ -84,7 +84,7 @@ func (d *DataFile) Read(pos int, size int) ([]byte, error) {
 	// Read the file with the given offset.
 	n, err := d.reader.ReadAt(record, start)
 	if err != nil {
-		return nil, fmt.Errorf("error reading data from file: %v", err)
+		return nil, err
 	}
 
 	// Check if the size of bytes read matches the record size.
@@ -115,6 +115,7 @@ func (d *DataFile) Close() error {
 	if err := d.writer.Close(); err != nil {
 		return err
 	}
+
 	if err := d.reader.Close(); err != nil {
 		return err
 	}

pkg/barrel/barrel.go

@@ -96,8 +96,8 @@ func Init(opts Opts) (*Barrel, error) {
 	// 	opts.MergeInterval = time.Second * 5
 	// }
 	// go barrel.MergeFiles(opts.MergeInterval)
-	// // Spawn a goroutine which checks for the file size of the active file at periodic interval.
-	// go barrel.ExamineFileSize(time.Minute * 1)
+	// Spawn a goroutine which checks for the file size of the active file at periodic interval.
+	go barrel.ExamineFileSize(time.Minute * 1)
 
 	return barrel, nil
 }

pkg/barrel/compact.go

@@ -1,16 +1,15 @@
 package barrel
 
 import (
+	"path/filepath"
 	"time"
 
 	"github.com/mr-karan/barreldb/internal/datafile"
 )
 
-// ExamineFileSize runs cleanup operations at every configured interval.
+// ExamineFileSize checks for file size at a periodic interval.
 // It examines the file size of the active db file and marks it as stale
 // if the file size exceeds the configured size.
-// Additionally it runs a merge operation which compacts the stale files.
-// This produces a hints file as well which is used for faster startup time.
 func (b *Barrel) ExamineFileSize(evalInterval time.Duration) {
 	var (
 		evalTicker = time.NewTicker(evalInterval).C
@@ -36,6 +35,7 @@ func (b *Barrel) rotateDF() error {
 	}
 
 	// If the file is below the threshold of max size, do no action.
+	b.lo.Debug("checking if db file has exceeded max_size", "current_size", size, "max_size", b.opts.MaxFileSize)
 	if size < b.opts.MaxFileSize {
 		return nil
 	}
@@ -61,3 +61,42 @@ func (b *Barrel) rotateDF() error {
 
 	return nil
 }
+
+// GenerateHints encodes the contents of the in-memory hashtable
+// as `gob` and writes the data to a hints file.
+func (b *Barrel) GenerateHints() error {
+	b.Lock()
+	defer b.Unlock()
+
+	path := filepath.Join(b.opts.Dir, HINTS_FILE)
+	if err := b.keydir.Encode(path); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// CleanupExpired removes the expired keys.
+func (b *Barrel) CleanupExpired() error {
+	b.Lock()
+	defer b.Unlock()
+
+	// Iterate over all keys and delete all keys which are expired.
+	for k := range b.keydir {
+		record, err := b.get(k)
+		if err != nil {
+			b.lo.Error("error fetching key", "key", k, "error", err)
+			continue
+		}
+		if record.isExpired() {
+			b.lo.Debug("deleting key since it's expired", "key", k)
+			// Delete the key.
+			if err := b.delete(k); err != nil {
+				b.lo.Error("error deleting key", "key", k, "error", err)
+				continue
+			}
+		}
+	}
+
+	return nil
+}

pkg/barrel/ops.go

@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"hash/crc32"
 	"time"
+
+	"github.com/mr-karan/barreldb/internal/datafile"
 )
 
 func (b *Barrel) get(k string) (Record, error) {
@@ -17,22 +19,37 @@ func (b *Barrel) get(k string) (Record, error) {
 	var (
 		// Header object for decoding the binary data into it.
 		header Header
+		reader *datafile.DataFile
 	)
 
+	// Set the current file ID as the default.
+	reader = b.df
+
+	// Check if the ID is different from the current ID.
+	if meta.FileID != b.df.ID() {
+		reader, ok = b.stale[meta.FileID]
+		if !ok {
+			return Record{}, fmt.Errorf("error looking up for the db file for the given id: %d", meta.FileID)
+		}
+		reader.Open()
+		defer reader.Close()
+	}
+
 	// Read the file with the given offset.
-	data, err := b.df.Read(meta.RecordPos, meta.RecordSize)
+	data, err := reader.Read(meta.RecordPos, meta.RecordSize)
 	if err != nil {
 		return Record{}, fmt.Errorf("error reading data from file: %v", err)
 	}
 
 	// Decode the header.
 	header.decode(data)
 
-	// Get the offset position in record to start reading the value from.
-	valPos := meta.RecordSize - int(header.ValSize)
-
-	// Read the value from the record.
-	val := data[valPos:]
+	var (
+		// Get the offset position in record to start reading the value from.
+		valPos = meta.RecordSize - int(header.ValSize)
+		// Read the value from the record.
+		val = data[valPos:]
+	)
 
 	record := Record{
 		Header: header,
@@ -52,7 +69,7 @@ func (b *Barrel) put(k string, val []byte, expiry *time.Time) error {
 		ValSize:   uint32(len(val)),
 	}
 
-	// Check for expiry
+	// Check for expiry.
 	if expiry != nil {
 		header.Expiry = uint32(expiry.Unix())
 	} else {
@@ -65,11 +82,10 @@ func (b *Barrel) put(k string, val []byte, expiry *time.Time) error {
 		Value: val,
 	}
 
-	// Create a buffer for writing data to it.
-	// buf := bytes.NewBuffer([]byte{})
-
+	// Get the buffer from the pool for writing data.
 	buf := b.bufPool.Get().(*bytes.Buffer)
 	defer b.bufPool.Put(buf)
+	// Resetting the buffer is important since the length of bytes written should be reset on each `set` operation.
 	defer buf.Reset()
 
 	// Encode header.