README
¶
WAL (Write ahead log)
wal is a write ahead log written in go.
Installation
The code was tested with go version 1.15.
Older versions can also work but have not been tested.
go get -u github.com/ljmsc/wal
Currently, only unix systems are supported.
Usage
Note: since version 0.7.0 the wal is no longer safe for concurrent write. It is up to the developer to protect the wal. e.g. Mutex, Channels. Since this kind of functionality is not always needed I removed it for performance's sake.
basic
package main
import (
"fmt"
"github.com/ljmsc/wal"
)
type entry []byte
func (t *entry) Unmarshal(_data []byte) error {
*t = _data
return nil
}
func main() {
storage, err := wal.Open("./path/to/wal", 4, 100)
if err != nil {
// handle error
panic(err)
}
defer storage.Close()
data := []byte("this is my awesome test data")
seqNum, err := storage.Write(data)
if err != nil {
// handle write error
panic(err)
}
fmt.Printf("successful wrote entry. Sequence Number: %d\n", seqNum)
re := entry{}
if err := storage.ReadAt(&re, seqNum); err != nil {
// handle error
panic(err)
}
fmt.Printf("successful read entry from log. value: %s \n", re)
}
License
The project (and all code) is licensed under the Mozilla Public License Version 2.0.
Documentation
¶
Index ¶
Constants ¶
This section is empty.
Variables ¶
Functions ¶
This section is empty.
Types ¶
type Wal ¶
type Wal interface {
// Name returns the name of the write ahead log
Name() string
// Read reads the data of the entry with the given sequence number and returns it
Read(_seqNum uint64) ([]byte, error)
// ReadAt reads the data of the entry with the given sequence number to _entry
// Deprecated
ReadAt(_entry Entry, _seqNum uint64) error
// ReadTo reads the data of the entry with the given sequence number to _entry
ReadTo(_entry encoding.BinaryUnmarshaler, _seqNum uint64) error
// ReadFrom reads the payload of _n entries starting from _seqNum
ReadFrom(_seqNum uint64, _n int64) (<-chan Envelope, error)
// Write writes the given data on disk and returns the new sequence number
Write(_data []byte) (uint64, error)
// WriteFrom extracts data from the given object and writes it on disk. it returns the new sequence number
WriteFrom(r encoding.BinaryMarshaler) (uint64, error)
// Truncate dumps all records whose sequence number is greater or equal to offsetByPos
Truncate(_seqNum uint64) error
// Sync flushes changes to persistent storage and returns the latest safe sequence number
Sync() (uint64, error)
// First returns the first sequence number in the write ahead log
First() uint64
// SeqNum returns the latest written sequence number in the write ahead log
SeqNum() uint64
// Safe returns the latest safe sequence number
Safe() uint64
// Close closes the write ahead log and all segment files
Close() error
}
Source Files
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