README.md

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Immuta is a Append Only Log implementation based on single writer, multiple readers concept. It uses filesystem as it's core the format of the each record is as follows and uses solid for io signgling

• the first 8 bytes provide the number of messages in the log file
• loop
  • the next 8 bytes define the size of the payload (Header)
  • payload can be any arbitrary size

+----------+----------+---------------+----------+---------------+
|          |          |               |          |               |
| MESSAGES |  PAYLOAD |    PAYLOAD    |  PAYLOAD |    PAYLOAD    | ...
|   COUNT  |   SIZE   |               |   SIZE   |               |
+----------+----------+---------------+----------+---------------+
   8 bytes   8 bytes                    8 bytes

Installation

go get ella.to/immuta

Usgae

package main

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"time"

	"ella.to/immuta"
)

func main() {
	filename := "./data.log"
	poolFileDescriptor := 10
	// fastwrite uses the buffer for each append
	// if you need gurrantee on saving on disk, enable set fastWrite to false
	// the Append operation will get the performance hit
	fastWrite := true

	log, err := immuta.New(filename, poolFileDescriptor, fastWrite)
	if err != nil {
		panic(err)
	}
	defer log.Close()

	content := []byte("hello world")

	// write to append only log
	index, size, err := log.Append(context.Background(), bytes.NewReader(content))
	if err != nil {
		panic(err)
	}

	if index != 8 {
		panic("index must be 8")
	}

	if size != 11 {
		panic("size must be 11")
	}

	// 0: start from beginning
	// negative value: start from latest append
	// positive number: skip those message
	var startPos int64 = 0

	// this call doesn't allocate any file descriptor yet
	stream := log.Stream(context.Background(), startPos)
	defer stream.Done()

	for {
		var buffer bytes.Buffer

		err := func() error {
			ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
			defer cancel()

			r, size, err := stream.Next(ctx)
			if err != nil {
				return err
			}
			// important: don't forget to call Done() to release the file descriptor
			defer r.Done()

			buffer.Reset()

			_, err = io.Copy(&buffer, r)
			if err != nil {
				return err
			}

			fmt.Printf("size of the record: %d\n", size)
			fmt.Printf("content: %s\n", buffer.String())

			return nil
		}()

		if errors.Is(err, context.DeadlineExceeded) {
			break
		} else if err != nil {
			panic(err)
		}
	}
}

Performance

• Appending 100k records of 1kb took around 1 seconds

go test -benchmem -run=^$ -bench ^Benchmark1kbAppend$ ella.to/immuta

goos: darwin
goarch: arm64
pkg: ella.to/immuta
cpu: Apple M2 Pro
Benchmark1kbAppend-12             103730              9882 ns/op              64 B/op          3 allocs/op

• Reading the 100k record is under 150ms

go test -timeout 30s -run ^TestRead100kMessages$ ella.to/immuta -v
=== RUN   TestRead100kMessages
time taken to write 100000: 895.478792ms
time taken to read 100000: 139.394542ms