logstore

README

LogStore

A partitioned & immutable append-only storage engine.

Why

It's meant for use with any system that wants to implement an append-only data structure that can be consumed in parallel by multiple consumers. The end goal is to use as backing store for a message queue i'm working on currently. Which will provide the distributed layer on top of it.

Features

• Very fast writes, because it only appends to the end of the partition.
• Very fast read, because it only reads sequentially.
• Support multiple concurrent readers via partitioning the log files.
• Guarantees order on the partition level only. Which eliminates the need for consensus.

Use Cases

• Commit Log
• Event Sourcing
• Binary Web Logs
• Message Queues

Example

    import (
        "fmt"
        "log"

        "github.com/lafikl/logstore"
    )

    func main() {
        lstore := logstore.New("logs/", 10)
        # appending logs
        pkey := "10084"
        lstore.Append(pkey, []byte("Hello World!"))

        // fetching a partition
        // index starts from 0.
        prtn, err := lstore.Partition(5)
        if err != nil {
            log.Fatal(err)
        }
        // hint:
        // you can use the prtn.Fd to send messages slices to other LogStore machines without copying data into use-space
        fmt.Println(prtn.Idx)

        // reading logs
        buff := make([]byte, 2024)
        partition := 0
        offset := int64(0)
        n, err := lstore.Read(partition, offset, buff)
        if err != nil {
            log.Fatal(err)
        }
        msgs, err := l.UnMarshal(b[:n])
        if err != nil {
            log.Fatal(err)
        }
        for idx, msgs := range msgs {
            fmt.Println(idx, string(msgs.Payload))
        }
    }

API Docs

GoDoc

Status

Still in a very early state. Don't use it with anything precious.

License

The MIT License (MIT)

Copyright (c) 2016 Khalid Lafi

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Documentation

Index

• Variables
• type LogStore
  • func New(dataDir string, partitions int) *LogStore
  • func (l *LogStore) Append(pkey string, payload []byte) (n int64, err error)
  • func (l *LogStore) Partition(idx int) (*Partition, error)
  • func (l *LogStore) Read(partition int, offset int64, buf []byte) (n int, err error)
  • func (l *LogStore) Setup()
  • func (l *LogStore) UnMarshal(b []byte) ([]*Message, error)
• type Message
• type Partition

Variables

var ErrNoPartition = errors.New("Partition doesn't exist")

ErrNoPartition is returned when the requested partition doesn't exist

var ErrShortPayload = errors.New("Too short payload of messages")

ErrShortPayload returned when UnMarshal is given a too small buffer of messages

Types

type LogStore

type LogStore struct {
	Partitions []*Partition
	// contains filtered or unexported fields
}

LogStore is an immutable append-only storage engine for logs.

func New

func New(dataDir string, partitions int) *LogStore

New returns a new LogStore instance

func (*LogStore) Append

func (l *LogStore) Append(pkey string, payload []byte) (n int64, err error)

Append appends the given message to the log file

func (*LogStore) Partition

func (l *LogStore) Partition(idx int) (*Partition, error)

Partition returns a refernce for the requested partition

func (*LogStore) Read

func (l *LogStore) Read(partition int, offset int64, buf []byte) (n int, err error)

func (*LogStore) Setup

func (l *LogStore) Setup()

Setup makes sure that all the files are in place

func (*LogStore) UnMarshal

func (l *LogStore) UnMarshal(b []byte) ([]*Message, error)

UnMarshal deserializes the given byte slice into Messages

type Message

type Message struct {
	Length   uint64
	Checksum uint32
	Payload  []byte
}

Message is a representation of what gets stored on disk

type Partition

type Partition struct {
	*sync.RWMutex
	Fd  *os.File
	Idx int
}

Partition bla bla