memcache

package
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 Go to latest Published: Dec 7, 2018 License: BSD-2-Clause Imports: 14 Imported by: 2

README 

Fast client and server implementations for memcache protocol.

The package contains the following client implementations:
  * Client - talks to a single memcache server.
  * DistributedClient - routes requests to multiple servers using consistent
    hashing. Supports addition/removal of servers on the fly.
  * CachingClient - saves network bandwidth between the client and servers
    by storing responses in local cache. Can talk only to servers supporting
    'conditional get' (cget) memcache extension.

Server implementation has the following features:
  * 'conditional get' (cget) memcache extension.
  * 'dogpile effect-aware get' (getde) memcache extension.

================================================================================
How to build and use it?

$ go get -u github.com/valyala/ybc/libs/go/memcache

Then import it into your program:

import "github.com/valyala/ybc/libs/go/memcache"

Documentation can be generated by:

$ go doc github.com/valyala/ybc/libs/go/memcache

or read at http://go.pkgdoc.org/github.com/valyala/ybc/libs/go/memcache .

================================================================================
FAQ

Q: Why didn't you implement 'replace', 'append', 'prepend', 'incr', 'decr'
   and 'touch' memcache commands?
A: Because I think they are useless for caching purposes.

Q: Your benchmarks show CachingClient is slower than simple Client. Then what's
   the purpose of CachingClient?
A: CachingClient saves network bandwidth between memcache servers
   and the client. It won't help much if memcache servers are located
   on the same machine as the client itself. But it can save a lot of bandwidth
   if you cache items with sizes exceeding ~100 bytes on memcache servers
   accessed over the network.
   CachingClient may also deliver much higher qps comparing to simple Client
   if CachingClient.SetWithValidateTtl*() functions are used intelligently
   with validateTtl values higher than 0.

Documentation

Overview

Package memcache provides fast client and server implementations for memcache.

Index

Constants

This section is empty.

Variables

View Source 
var (
	ErrCacheMiss            = errors.New("memcache.Client: cache miss")
	ErrCasidMismatch        = errors.New("memcache.Client: casid mismatch")
	ErrClientNotRunning     = errors.New("memcache.Client: the client isn't running")
	ErrCommunicationFailure = errors.New("memcache.Client: communication failure")
	ErrMalformedKey         = errors.New("memcache.Client: malformed key")
	ErrNilValue             = errors.New("memcache.Client: nil value")
	ErrNotModified          = errors.New("memcache.Client: item not modified")
	ErrAlreadyExists        = errors.New("memcache.Client: the item already exists")
)
View Source 
var (
	ErrNoServers = errors.New("memcache.DistributedClient: there are no registered servers")
)

Functions

This section is empty.

Types

type Cacher 

type Cacher interface {
	Ccacher

	Start()
	Stop()
}

Client and DistributedClient implement this interface.

type CachingClient 

type CachingClient struct {
	// The underlying memcache client.
	//
	// The client must be initialized before passing it here.
	//
	// Currently Client and DistributedClient may be passed here.
	Client Ccacher

	// The underlying local cache.
	//
	// The cache should be initialized before passing it here.
	//
	// Currently ybc.Cache and ybc.Cluster may be passed here.
	Cache ybc.Cacher
}

Memcache client with in-process data caching.

It can save network bandwidth between the client and memcache servers.

The client uses approach similar to HTTP cache validation with entity tags - see http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.11 .

Usage: 

cache := openCache()
defer cache.Close()

client.Start()
defer client.Stop()

c := memcache.CachingClient{
    Client: client,
    Cache:  cache,
}

item := memcache.Item{
    Key:   []byte("key"),
    Value: []byte("value"),
}
if err := c.Set(&item); err != nil {
    log.Fatalf("Error in c.Set(): %s", err)
}
if err := c.Get(&item); err != nil {
    log.Fatalf("Error in c.Get(): %s", err)
}

func (*CachingClient) Add 

func (c *CachingClient) Add(item *Item) error

See Client.Add()

func (*CachingClient) AddWithValidateTtl 

func (c *CachingClient) AddWithValidateTtl(item *Item, validateTtl time.Duration) error

The same as CachingClient.Add(), but sets interval for periodic item revalidation on the server.

This means that outdated, locally cached version of the item may be returned during validateTtl interval. Use CachingClient.Add() if you don't unserstand how this works.

Setting validateTtl to 0 leads to item re-validation on every get() request. This is equivalent ot CachingClient.Add() call. Even in this scenario network bandwidth between the client and memcache servers is saved if the average item size exceeds ~100 bytes.

func (*CachingClient) Cas 

func (c *CachingClient) Cas(item *Item) error

See Client.Cas()

func (*CachingClient) CasWithValidateTtl 

func (c *CachingClient) CasWithValidateTtl(item *Item, validateTtl time.Duration) error

The same as CachingClient.Cas(), but sets interval for periodic item revalidation on the server.

This means that outdated, locally cached version of the item may be returned during validateTtl interval. Use CachingClient.Cas() if you don't unserstand how this works.

Setting validateTtl to 0 leads to item re-validation on every get() request. This is equivalent ot CachingClient.Cas() call. Even in this scenario network bandwidth between the client and memcache servers is saved if the average item size exceeds ~100 bytes.

func (*CachingClient) Delete 

func (c *CachingClient) Delete(key []byte) error

See Client.Delete()

func (*CachingClient) DeleteNowait 

func (c *CachingClient) DeleteNowait(key []byte)

See Client.DeleteNowait()

func (*CachingClient) FlushAll 

func (c *CachingClient) FlushAll() error

See Client.FlushAll()

func (*CachingClient) FlushAllDelayed 

func (c *CachingClient) FlushAllDelayed(expiration time.Duration) error

See Client.FlushAllDelayed()

func (*CachingClient) FlushAllDelayedNowait 

func (c *CachingClient) FlushAllDelayedNowait(expiration time.Duration)

See Client.FlushAllDelayedNowait()

func (*CachingClient) FlushAllNowait 

func (c *CachingClient) FlushAllNowait()

See Client.FlushAllNowait()

func (*CachingClient) Get 

func (c *CachingClient) Get(item *Item) error

See Client.Get()

func (*CachingClient) GetDe 

func (c *CachingClient) GetDe(item *Item, graceDuration time.Duration) error

See Client.GetDe()

func (*CachingClient) GetMulti 

func (c *CachingClient) GetMulti(items []Item) error

See Client.GetMulti()

func (*CachingClient) Set 

func (c *CachingClient) Set(item *Item) error

See Client.Set()

func (*CachingClient) SetNowait 

func (c *CachingClient) SetNowait(item *Item)

See Client.SetNowait()

func (*CachingClient) SetWithValidateTtl 

func (c *CachingClient) SetWithValidateTtl(item *Item, validateTtl time.Duration) error

The same as CachingClient.Set(), but sets interval for periodic item revalidation on the server.

This means that outdated, locally cached version of the item may be returned during validateTtl interval. Use CachingClient.Set() if you don't understand how this works.

Setting validateTtl to 0 leads to item re-validation on every get() request. This is equivalent to CachingClient.Set() call. Even in this scenario network bandiwdth between the client and memcache servers is saved if the average item size exceeds ~100 bytes.

func (*CachingClient) SetWithValidateTtlNowait 

func (c *CachingClient) SetWithValidateTtlNowait(item *Item, validateTtl time.Duration)

The same as CachingClient.SetWithValidateTtl(), but doesn't wait for completion of the operation.

type Ccacher 

type Ccacher interface {
	MemcacherDe

	Cget(item *Item) error
	CgetDe(item *Item, graceDuration time.Duration) error
}

Client and DistributedClient implement this interface.

type Client 

type Client struct {
	ClientConfig

	// TCP address of memcached server to connect to.
	// Required parameter.
	//
	// The address should be in the form addr:port.
	ServerAddr string
	// contains filtered or unexported fields
}

Fast memcache client.

The client is goroutine-safe. It is designed to work fast when hundreds concurrent goroutines are calling simultaneously its' methods.

The client works with a single memcached server. Use DistributedClient if you want working with multiple servers.

Usage: 

c := Client{
    ServerAddr: ":11211",
}
c.Start()
defer c.Stop()

item := Item{
    Key:   []byte("key"),
    Value: []byte("value"),
}
if err := c.Set(&item); err != nil {
    handleError(err)
}
if err := c.Get(&item); err != nil {
    handleError(err)
}

func (*Client) Add 

func (c *Client) Add(item *Item) error

Stores the given item only if the server doesn't already hold data under the item.Key.

Returns ErrAlreadyExists error if the server already holds data under the item.Key.

func (*Client) Cas 

func (c *Client) Cas(item *Item) error

Stores the given item only if item.Casid matches casid for the given item on the server.

Returns ErrCacheMiss if the server has no item with such a key. Returns ErrCasidMismatch if item on the server has other casid value.

func (*Client) Cget 

func (c *Client) Cget(item *Item) error

Performs conditional get request for the given item.Key and item.Casid.

This is an extension to memcache protocol, so it isn't supported by the original memcache server.

Fills item.Value, item.Flags and item.Casid only on cache hit and only if the given casid doesn't match the casid on the server, i.e. if the server contains new value for the given key.

Returns ErrCacheMiss on cache miss. Returns ErrNotModified if the corresponding item on the server has the same casid (i.e. the item wasn't modified).

Client.Cget() is intended for reducing network bandwidth consumption in multi-level caches. It is modelled after HTTP cache validation approach with entity tags - see http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.11 .

func (*Client) CgetDe 

func (c *Client) CgetDe(item *Item, graceDuration time.Duration) error

Combines functionality of Client.Cget() and Client.GetDe().

func (*Client) Delete 

func (c *Client) Delete(key []byte) error

Deletes an item with the given key from memcache server.

Returns ErrCacheMiss if there were no item with such key on the server.

func (*Client) DeleteNowait 

func (c *Client) DeleteNowait(key []byte)

The same as Client.Delete(), but doesn't wait for operation completion.

Do not modify slice pointed by key after passing to this function - it actually becomes an owner of this slice.

func (*Client) FlushAll 

func (c *Client) FlushAll() error

Flushes all the items on the server.

func (*Client) FlushAllDelayed 

func (c *Client) FlushAllDelayed(expiration time.Duration) error

Flushes all the items on the server after the given expiration delay.

func (*Client) FlushAllDelayedNowait 

func (c *Client) FlushAllDelayedNowait(expiration time.Duration)

The same as Client.FlushAllDelayed(), but doesn't wait for operation completion.

func (*Client) FlushAllNowait 

func (c *Client) FlushAllNowait()

The same as Client.FlushAll(), but doesn't wait for operation completion.

func (*Client) Get 

func (c *Client) Get(item *Item) error

Obtains item.Value, item.Flags and item.Casid for the given item.Key.

Returns ErrCacheMiss on cache miss.

func (*Client) GetDe 

func (c *Client) GetDe(item *Item, graceDuration time.Duration) error

Performs dogpile effect-aware get for the given item.Key.

This is an extension to memcache protocol, so it isn't supported by the original memcache server.

Returns ErrCacheMiss on cache miss. It is expected that the caller will create and store in the cache an item on cache miss during the given graceDuration interval.

func (*Client) GetMulti 

func (c *Client) GetMulti(items []Item) error

Obtains multiple items associated with the the corresponding keys.

Sets Item.Value, Item.Flags and Item.Casid for each returned item. Doesn't modify Item.Value and Item.Flags for items missing on the server.

func (*Client) Set 

func (c *Client) Set(item *Item) error

Stores the given item in the memcache server.

func (*Client) SetNowait 

func (c *Client) SetNowait(item *Item)

The same as Client.Set(), but doesn't wait for operation completion.

Do not modify slices pointed by item.Key and item.Value after passing to this function - it actually becomes an owner of these slices.

func (*Client) Start 

func (c *Client) Start()

Starts the given client.

No longer needed clients must be stopped via Client.Stop() call.

func (*Client) Stop 

func (c *Client) Stop()

Stops the given client, which has been started via Client.Start() call.

type ClientConfig 

type ClientConfig struct {
	// The number of simultaneous TCP connections to establish
	// to memcached server.
	// Optional parameter.
	//
	// The Client is able to squeeze out impossible from a single
	// connection by pipelining a ton of requests on it.
	// Multiple simultaneous connections may be required in the following
	// cases:
	//   * If memcached server delays incoming requests' execution.
	//     Since memcached protocol doesn't allow out-of-order requests'
	//     execution, a single slow request may delay execution of all
	//     the requests pipelined on the connection after it.
	//     Multiple concurrent connections may help in such a situation.
	//   * If memcached server runs on multi-CPU system, but uses a single
	//     CPU (thread) per connection.
	ConnectionsCount int

	// The maximum number of pending requests awaiting to be processed
	// by memcached server.
	// Optional parameter.
	MaxPendingRequestsCount int

	// The size in bytes of buffer used by the Client for reading responses
	// received from memcached per connection.
	// Optional parameter.
	ReadBufferSize int

	// The size in bytes of buffer used by the Client for writing requests
	// to be sent to memcached per connection.
	// Optional parameter.
	WriteBufferSize int

	// The size in bytes of OS-supplied read buffer per TCP connection.
	// Optional parameter.
	OSReadBufferSize int

	// The size in bytes of OS-supplied write buffer per TCP connection.
	// Optional parameter.
	OSWriteBufferSize int
}

Memcache client configuration. Can be passed to Client and DistributedClient.

type DistributedClient 

type DistributedClient struct {
	ClientConfig
	// contains filtered or unexported fields
}

Memcache client, which can shard requests to multiple servers using consistent hashing.

Servers may be dynamically added and deleted at any time via AddServer() and DeleteServer() functions if the client is started via Start() call.

The client is goroutine-safe.

Usage: 

c := DistributedClient{}
c.StartStatic([]string{"host1:11211", "host2:11211", "host3:11211"})
defer c.Stop()

item := Item{
    Key:   []byte("key"),
    Value: []byte("value"),
}
if err := c.Set(&item); err != nil {
    handleError(err)
}
if err := c.Get(&item); err != nil {
    handleError(err)
}

func (*DistributedClient) Add 

func (c *DistributedClient) Add(item *Item) (err error)

See Client.Add().

func (*DistributedClient) AddServer 

func (c *DistributedClient) AddServer(serverAddr string)

Dynamically adds the given server to the client.

serverAddr must be in the form 'host:port'.

This function may be called only if the client has been started via DistributedClient.Start() call, not via DistributedClient.StartStatic() call!

Added servers may be removed at any time via DistributedClient.DeleteServer() call.

func (*DistributedClient) Cas 

func (c *DistributedClient) Cas(item *Item) (err error)

See Client.Cas()

func (*DistributedClient) Cget 

func (c *DistributedClient) Cget(item *Item) (err error)

See Client.Cget().

func (*DistributedClient) CgetDe 

func (c *DistributedClient) CgetDe(item *Item, graceDuration time.Duration) (err error)

See Client.CgetDe()

func (*DistributedClient) Delete 

func (c *DistributedClient) Delete(key []byte) (err error)

See Client.Delete().

func (*DistributedClient) DeleteNowait 

func (c *DistributedClient) DeleteNowait(key []byte)

See Client.DeleteNowait().

func (*DistributedClient) DeleteServer 

func (c *DistributedClient) DeleteServer(serverAddr string)

Dynamically removes the given server from the client.

serverAddr must be in the form 'host:port'

This function may be called only if the client has been started via DistributedClient.Start() call, not via DistributedClient.StartStatic() call!

func (*DistributedClient) FlushAll 

func (c *DistributedClient) FlushAll() (err error)

See Client.FlushAll().

func (*DistributedClient) FlushAllDelayed 

func (c *DistributedClient) FlushAllDelayed(expiration time.Duration) (err error)

See Client.FlushAllDelayed().

func (*DistributedClient) FlushAllDelayedNowait 

func (c *DistributedClient) FlushAllDelayedNowait(expiration time.Duration)

See Client.FlushAllDelayedNowait().

func (*DistributedClient) FlushAllNowait 

func (c *DistributedClient) FlushAllNowait()

See Client.FlushAllNowait().

func (*DistributedClient) Get 

func (c *DistributedClient) Get(item *Item) (err error)

See Client.Get().

func (*DistributedClient) GetDe 

func (c *DistributedClient) GetDe(item *Item, graceDuration time.Duration) (err error)

See Client.GetDe().

func (*DistributedClient) GetMulti 

func (c *DistributedClient) GetMulti(items []Item) (err error)

See Client.GetMulti().

func (*DistributedClient) Set 

func (c *DistributedClient) Set(item *Item) (err error)

See Client.Set().

func (*DistributedClient) SetNowait 

func (c *DistributedClient) SetNowait(item *Item)

See Client.SetNowait().

func (*DistributedClient) Start 

func (c *DistributedClient) Start()

Starts distributed client with the ability to dynamically add/remove servers via DistributedClient.AddServer() and DistributedClient.DeleteServer().

Started client must be stopped via c.Stop() call when no longer needed!

Use DistributedClient.StartStatic() if you don't plan dynamically adding/removing servers to/from the client. The resulting static client may work faster than the dynamic client.

func (*DistributedClient) StartStatic 

func (c *DistributedClient) StartStatic(serverAddrs []string)

Starts distributed client connected to the given memcache servers.

Each serverAddr must be in the form 'host:port'.

Started client must be stopped via DistributedClient.Stop() call when no longer needed.

Use DistributedClient.Start() if you plan dynamically adding/removing servers to/from the client. Note that the resuling dynamic client may work a bit slower than the static client.

func (*DistributedClient) Stop 

func (c *DistributedClient) Stop()

Stops distributed client.

type Item 

type Item struct {
	// Item's key.
	// Required parameter.
	Key []byte

	// Item's value.
	//
	// The Value is required in set()-type requests and isn't required in
	// get()-type requests.
	Value []byte

	// Expiration time for the item.
	// Zero means the item has no expiration time.
	//
	// The Expiration is used only in set()-type requests.
	Expiration time.Duration

	// An opaque value, which is passed to/from memcache.
	// Optional parameter.
	Flags uint32

	// This field is filled by get()-type requests and should be passed
	// to Cas() and Cget*() requests.
	Casid uint64
}

Memcache item.

type Memcacher 

type Memcacher interface {
	Get(item *Item) error
	GetMulti(items []Item) error
	Set(item *Item) error
	SetNowait(item *Item)
	Delete(key []byte) error
	DeleteNowait(key []byte)
	Add(item *Item) error
	Cas(item *Item) error
	FlushAll() error
	FlushAllNowait()
	FlushAllDelayed(expiration time.Duration) error
	FlushAllDelayedNowait(expiration time.Duration)
}

Client, DistributedClient and CachingClient implement this interface.

type MemcacherDe 

type MemcacherDe interface {
	Memcacher

	GetDe(item *Item, graceDuration time.Duration) error
}

Client, DistributedClient and CachingClient implement this interface.

type Server 

type Server struct {
	// The underlying cache storage.
	// Required parameter.
	//
	// The cache must be initialized before passing it here.
	//
	// Currently ybc.Cache and ybc.Cluster may be passed here.
	Cache ybc.Cacher

	// TCP address to listen to. Must be in the form addr:port.
	// Required parameter.
	ListenAddr string

	// The size of buffer used for reading requests from clients
	// per each connection.
	// Optional parameter.
	ReadBufferSize int

	// The size of buffer used for writing responses to clients
	// per each connection.
	// Optional parameter.
	WriteBufferSize int

	// The size in bytes of OS-supplied read buffer per TCP connection.
	// Optional parameter.
	OSReadBufferSize int

	// The size in bytes of OS-supplied write buffer per TCP connection.
	// Optional parameter.
	OSWriteBufferSize int
	// contains filtered or unexported fields
}

Memcache server.

Usage: 

cache := openCache()
defer cache.Close()

s := Server{
    Cache: cache,
    ListenAddr: ":11211",
}
if err := s.Serve(); err != nil {
    handleError(err)
}

func (*Server) Serve 

func (s *Server) Serve() error

Start the server and waits until it is stopped via Server.Stop() call.

func (*Server) Start 

func (s *Server) Start()

Starts the given server.

No longer needed servers must be stopped via Server.Stop() call.

func (*Server) Stop 

func (s *Server) Stop()

Stops the server, which has been started via either Server.Start() or Server.Serve() calls.

Don't forget closing the Server.Cache, since the server doesn't close it automatically.

func (*Server) Wait 

func (s *Server) Wait() error

Waits until the server is stopped.

Source Files

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