memtable

README

Library for Consistent Cache

Based on the freecache library and the 'leasing' mechanism of the paper Scaling Memcache at Facebook.

Usage

cacheSize := 100 * 1024 * 1024 // 100MB
cache := memtable.New(cacheSize)

for {
    key := []byte("some-key")
    result := cache.Get(key)
    if result.Status == memtable.GetStatusLeaseRejected {
    	time.Sleep(100 * time.Millisecond)
    	continue
    }
    
    if result.Status == memtable.GetStatusFound {
    	// cache hit
    	fmt.Println("Got value:", result.Value)
    	return
    }
    
    // cache miss but lease is granted
    // get data from database
    value := []byte("some-value")
    
    affected := cache.Set(key, result.LeaseID, value)
    fmt.Println("Affected:", affected)
    return
}

License

The MIT License

Documentation

Index

• type GetResult
• type GetStatus
• type Memtable
  • func New(memsize int, options ...Option) *Memtable
  • func (m *Memtable) Get(key []byte) GetResult
  • func (m *Memtable) GetUnsafeInnerCache() *freecache.Cache
  • func (m *Memtable) Invalidate(key []byte) (affected bool)
  • func (m *Memtable) Set(key []byte, leaseID uint32, value []byte) (affected bool)
• type Option
  • func WithLeaseListSize(n uint32) Option
  • func WithLeaseTimeout(d uint32) Option
  • func WithNumBuckets(n uint32) Option

Types

type GetResult

type GetResult struct {
	Value   []byte
	LeaseID uint32
	Status  GetStatus
}

GetResult for result when calling Get

type GetStatus

type GetStatus int

GetStatus for cache Get

const (
	// GetStatusFound for normal cache hit case
	GetStatusFound GetStatus = iota
	// GetStatusLeaseGranted when cache miss and lease is granted
	GetStatusLeaseGranted
	// GetStatusLeaseRejected when cache miss and lease is not granted
	GetStatusLeaseRejected
)

type Memtable

type Memtable struct {
	// contains filtered or unexported fields
}

Memtable ...

func New

func New(memsize int, options ...Option) *Memtable

New ...

func (*Memtable) Get

func (m *Memtable) Get(key []byte) GetResult

Get value from the cache

func (*Memtable) GetUnsafeInnerCache

func (m *Memtable) GetUnsafeInnerCache() *freecache.Cache

GetUnsafeInnerCache returns the freecache

func (*Memtable) Invalidate

func (m *Memtable) Invalidate(key []byte) (affected bool)

Invalidate an entry from the cache

func (*Memtable) Set

func (m *Memtable) Set(key []byte, leaseID uint32, value []byte) (affected bool)

Set value to the cache

type Option

type Option func(opts *memtableOptions)

Option ...

func WithLeaseListSize

func WithLeaseListSize(n uint32) Option

WithLeaseListSize configures the number of entries in a lease list

func WithLeaseTimeout

func WithLeaseTimeout(d uint32) Option

WithLeaseTimeout for duration of lease timeout, in second

func WithNumBuckets

func WithNumBuckets(n uint32) Option

WithNumBuckets configures number of lease buckets