redis

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 Go to latest Published: Jun 1, 2016 License: Apache-2.0 Imports: 17 Imported by: 0

Documentation

Overview

Package redis is a client for the Redis database.

The Redigo FAQ (https://github.com/garyburd/redigo/wiki/FAQ) contains more documentation about this package.

Connections

The Conn interface is the primary interface for working with Redis. Applications create connections by calling the Dial, DialWithTimeout or NewConn functions. In the future, functions will be added for creating sharded and other types of connections.

The application must call the connection Close method when the application is done with the connection.

Executing Commands

The Conn interface has a generic method for executing Redis commands: 

Do(commandName string, args ...interface{}) (reply interface{}, err error)

The Redis command reference (http://redis.io/commands) lists the available commands. An example of using the Redis APPEND command is: 

n, err := conn.Do("APPEND", "key", "value")

The Do method converts command arguments to binary strings for transmission to the server as follows: 

Go Type                 Conversion
[]byte                  Sent as is
string                  Sent as is
int, int64              strconv.FormatInt(v)
float64                 strconv.FormatFloat(v, 'g', -1, 64)
bool                    true -> "1", false -> "0"
nil                     ""
all other types         fmt.Print(v)

Redis command reply types are represented using the following Go types: 

Redis type              Go type
error                   redis.Error
integer                 int64
simple string           string
bulk string             []byte or nil if value not present.
array                   []interface{} or nil if value not present.

Use type assertions or the reply helper functions to convert from interface{} to the specific Go type for the command result.

Pipelining

Connections support pipelining using the Send, Flush and Receive methods. 

Send(commandName string, args ...interface{}) error
Flush() error
Receive() (reply interface{}, err error)

Send writes the command to the connection's output buffer. Flush flushes the connection's output buffer to the server. Receive reads a single reply from the server. The following example shows a simple pipeline. 

c.Send("SET", "foo", "bar")
c.Send("GET", "foo")
c.Flush()
c.Receive() // reply from SET
v, err = c.Receive() // reply from GET

The Do method combines the functionality of the Send, Flush and Receive methods. The Do method starts by writing the command and flushing the output buffer. Next, the Do method receives all pending replies including the reply for the command just sent by Do. If any of the received replies is an error, then Do returns the error. If there are no errors, then Do returns the last reply. If the command argument to the Do method is "", then the Do method will flush the output buffer and receive pending replies without sending a command.

Use the Send and Do methods to implement pipelined transactions. 

c.Send("MULTI")
c.Send("INCR", "foo")
c.Send("INCR", "bar")
r, err := c.Do("EXEC")
fmt.Println(r) // prints [1, 1]

Concurrency

Connections do not support concurrent calls to the write methods (Send, Flush) or concurrent calls to the read method (Receive). Connections do allow a concurrent reader and writer.

Because the Do method combines the functionality of Send, Flush and Receive, the Do method cannot be called concurrently with the other methods.

For full concurrent access to Redis, use the thread-safe Pool to get and release connections from within a goroutine.

Publish and Subscribe

Use the Send, Flush and Receive methods to implement Pub/Sub subscribers. 

c.Send("SUBSCRIBE", "example")
c.Flush()
for {
    reply, err := c.Receive()
    if err != nil {
        return err
    }
    // process pushed message
}

The PubSubConn type wraps a Conn with convenience methods for implementing subscribers. The Subscribe, PSubscribe, Unsubscribe and PUnsubscribe methods send and flush a subscription management command. The receive method converts a pushed message to convenient types for use in a type switch. 

psc := redis.PubSubConn{c}
psc.Subscribe("example")
for {
    switch v := psc.Receive().(type) {
    case redis.Message:
        fmt.Printf("%s: message: %s\n", v.Channel, v.Data)
    case redis.Subscription:
        fmt.Printf("%s: %s %d\n", v.Channel, v.Kind, v.Count)
    case error:
        return v
    }
}

Reply Helpers

The Bool, Int, Bytes, String, Strings and Values functions convert a reply to a value of a specific type. To allow convenient wrapping of calls to the connection Do and Receive methods, the functions take a second argument of type error. If the error is non-nil, then the helper function returns the error. If the error is nil, the function converts the reply to the specified type: 

exists, err := redis.Bool(c.Do("EXISTS", "foo"))
if err != nil {
    // handle error return from c.Do or type conversion error.
}

The Scan function converts elements of a array reply to Go types: 

var value1 int
var value2 string
reply, err := redis.Values(c.Do("MGET", "key1", "key2"))
if err != nil {
    // handle error
}
 if _, err := redis.Scan(reply, &value1, &value2); err != nil {
    // handle error
}

Index

Constants

This section is empty.

Variables

View Source 
var ErrNil = errors.New("redigo: nil returned")

ErrNil indicates that a reply value is nil.

View Source 
var ErrPoolExhausted = errors.New("redigo: connection pool exhausted")

ErrPoolExhausted is returned from a pool connection method (Do, Send, Receive, Flush, Err) when the maximum number of database connections in the pool has been reached.

Functions

func Bool 

func Bool(reply interface{}, err error) (bool, error)

Bool is a helper that converts a command reply to a boolean. If err is not equal to nil, then Bool returns false, err. Otherwise Bool converts the reply to boolean as follows: 

Reply type      Result
integer         value != 0, nil
bulk string     strconv.ParseBool(reply)
nil             false, ErrNil
other           false, error

func Bytes 

func Bytes(reply interface{}, err error) ([]byte, error)

Bytes is a helper that converts a command reply to a slice of bytes. If err is not equal to nil, then Bytes returns nil, err. Otherwise Bytes converts the reply to a slice of bytes as follows: 

Reply type      Result
bulk string     reply, nil
simple string   []byte(reply), nil
nil             nil, ErrNil
other           nil, error

func Float64 

func Float64(reply interface{}, err error) (float64, error)

Float64 is a helper that converts a command reply to 64 bit float. If err is not equal to nil, then Float64 returns 0, err. Otherwise, Float64 converts the reply to an int as follows: 

Reply type    Result
bulk string   parsed reply, nil
nil           0, ErrNil
other         0, error

func Int 

func Int(reply interface{}, err error) (int, error)

Int is a helper that converts a command reply to an integer. If err is not equal to nil, then Int returns 0, err. Otherwise, Int converts the reply to an int as follows: 

Reply type    Result
integer       int(reply), nil
bulk string   parsed reply, nil
nil           0, ErrNil
other         0, error

func Int64 

func Int64(reply interface{}, err error) (int64, error)

Int64 is a helper that converts a command reply to 64 bit integer. If err is not equal to nil, then Int returns 0, err. Otherwise, Int64 converts the reply to an int64 as follows: 

Reply type    Result
integer       reply, nil
bulk string   parsed reply, nil
nil           0, ErrNil
other         0, error

func Ints 

func Ints(reply interface{}, err error) ([]int, error)

Ints is a helper that converts an array command reply to a []int. If err is not equal to nil, then Ints returns nil, err.

func MultiBulk 

func MultiBulk(reply interface{}, err error) ([]interface{}, error)

MultiBulk is deprecated. Use Values.

func Scan 

func Scan(src []interface{}, dest ...interface{}) ([]interface{}, error)

Scan copies from src to the values pointed at by dest.

The values pointed at by dest must be an integer, float, boolean, string, []byte, interface{} or slices of these types. Scan uses the standard strconv package to convert bulk strings to numeric and boolean types.

If a dest value is nil, then the corresponding src value is skipped.

If a src element is nil, then the corresponding dest value is not modified.

To enable easy use of Scan in a loop, Scan returns the slice of src following the copied values.

func ScanSlice 

func ScanSlice(src []interface{}, dest interface{}, fieldNames ...string) error

ScanSlice scans src to the slice pointed to by dest. The elements the dest slice must be integer, float, boolean, string, struct or pointer to struct values.

Struct fields must be integer, float, boolean or string values. All struct fields are used unless a subset is specified using fieldNames.

func ScanStruct 

func ScanStruct(src []interface{}, dest interface{}) error

ScanStruct scans alternating names and values from src to a struct. The HGETALL and CONFIG GET commands return replies in this format.

ScanStruct uses exported field names to match values in the response. Use 'redis' field tag to override the name: 

Field int `redis:"myName"`

Fields with the tag redis:"-" are ignored.

Integer, float, boolean, string and []byte fields are supported. Scan uses the standard strconv package to convert bulk string values to numeric and boolean types.

If a src element is nil, then the corresponding field is not modified.

func String 

func String(reply interface{}, err error) (string, error)

String is a helper that converts a command reply to a string. If err is not equal to nil, then String returns "", err. Otherwise String converts the reply to a string as follows: 

Reply type      Result
bulk string     string(reply), nil
simple string   reply, nil
nil             "",  ErrNil
other           "",  error

func StringMap 

func StringMap(result interface{}, err error) (map[string]string, error)

StringMap is a helper that converts an array of strings (alternating key, value) into a map[string]string. The HGETALL and CONFIG GET commands return replies in this format. Requires an even number of values in result.

func Strings 

func Strings(reply interface{}, err error) ([]string, error)

Strings is a helper that converts an array command reply to a []string. If err is not equal to nil, then Strings returns nil, err. Nil array items are converted to "" in the output slice. Strings returns an error if an array item is not a bulk string or nil.

func Uint64 

func Uint64(reply interface{}, err error) (uint64, error)

Uint64 is a helper that converts a command reply to 64 bit integer. If err is not equal to nil, then Int returns 0, err. Otherwise, Int64 converts the reply to an int64 as follows: 

Reply type    Result
integer       reply, nil
bulk string   parsed reply, nil
nil           0, ErrNil
other         0, error

func Values 

func Values(reply interface{}, err error) ([]interface{}, error)

Values is a helper that converts an array command reply to a []interface{}. If err is not equal to nil, then Values returns nil, err. Otherwise, Values converts the reply as follows: 

Reply type      Result
array           reply, nil
nil             nil, ErrNil
other           nil, error

Types

type Args 

type Args []interface{}

Args is a helper for constructing command arguments from structured values.

func (Args) Add 

func (args Args) Add(value ...interface{}) Args

Add returns the result of appending value to args.

func (Args) AddFlat 

func (args Args) AddFlat(v interface{}) Args

AddFlat returns the result of appending the flattened value of v to args.

Maps are flattened by appending the alternating keys and map values to args.

Slices are flattened by appending the slice elements to args.

Structs are flattened by appending the alternating names and values of exported fields to args. If v is a nil struct pointer, then nothing is appended. The 'redis' field tag overrides struct field names. See ScanStruct for more information on the use of the 'redis' field tag.

Other types are appended to args as is.

type Conn 

type Conn interface {
	// Close closes the connection.
	Close() error

	// Err returns a non-nil value if the connection is broken. The returned
	// value is either the first non-nil value returned from the underlying
	// network connection or a protocol parsing error. Applications should
	// close broken connections.
	Err() error

	// Do sends a command to the server and returns the received reply.
	Do(commandName string, args ...interface{}) (reply interface{}, err error)

	// Send writes the command to the client's output buffer.
	Send(commandName string, args ...interface{}) error

	// Flush flushes the output buffer to the Redis server.
	Flush() error

	// Receive receives a single reply from the Redis server
	Receive() (reply interface{}, err error)
}

Conn represents a connection to a Redis server.

func Dial 

func Dial(network, address string) (Conn, error)

Dial connects to the Redis server at the given network and address.

func DialTimeout 

func DialTimeout(network, address string, connectTimeout, readTimeout, writeTimeout time.Duration) (Conn, error)

DialTimeout acts like Dial but takes timeouts for establishing the connection to the server, writing a command and reading a reply.

func NewConn 

func NewConn(netConn net.Conn, readTimeout, writeTimeout time.Duration) Conn

NewConn returns a new Redigo connection for the given net connection.

func NewLoggingConn 

func NewLoggingConn(conn Conn, logger *log.Logger, prefix string) Conn

NewLoggingConn returns a logging wrapper around a connection.

type Error 

type Error string

Error represents an error returned in a command reply.

func (Error) Error 

func (err Error) Error() string

type Message 

type Message struct {

	// The originating channel.
	Channel string

	// The message data.
	Data []byte
}

Message represents a message notification.

type PMessage 

type PMessage struct {

	// The matched pattern.
	Pattern string

	// The originating channel.
	Channel string

	// The message data.
	Data []byte
}

PMessage represents a pmessage notification.

type Pool 

type Pool struct {

	// Dial is an application supplied function for creating and configuring a
	// connection
	Dial func() (Conn, error)

	// TestOnBorrow is an optional application supplied function for checking
	// the health of an idle connection before the connection is used again by
	// the application. Argument t is the time that the connection was returned
	// to the pool. If the function returns an error, then the connection is
	// closed.
	TestOnBorrow func(c Conn, t time.Time) error

	// Maximum number of idle connections in the pool.
	MaxIdle int

	// Maximum number of connections allocated by the pool at a given time.
	// When zero, there is no limit on the number of connections in the pool.
	MaxActive int

	// Close connections after remaining idle for this duration. If the value
	// is zero, then idle connections are not closed. Applications should set
	// the timeout to a value less than the server's timeout.
	IdleTimeout time.Duration

	// If Wait is true and the pool is at the MaxIdle limit, then Get() waits
	// for a connection to be returned to the pool before returning.
	Wait bool
	// contains filtered or unexported fields
}

Pool maintains a pool of connections. The application calls the Get method to get a connection from the pool and the connection's Close method to return the connection's resources to the pool.

The following example shows how to use a pool in a web application. The application creates a pool at application startup and makes it available to request handlers using a global variable. 

func newPool(server, password string) *redis.Pool {
    return &redis.Pool{
        MaxIdle: 3,
        IdleTimeout: 240 * time.Second,
        Dial: func () (redis.Conn, error) {
            c, err := redis.Dial("tcp", server)
            if err != nil {
                return nil, err
            }
            if _, err := c.Do("AUTH", password); err != nil {
                c.Close()
                return nil, err
            }
            return c, err
        },
        TestOnBorrow: func(c redis.Conn, t time.Time) error {
            _, err := c.Do("PING")
            return err
        },
    }
}

var (
    pool *redis.Pool
    redisServer = flag.String("redisServer", ":6379", "")
    redisPassword = flag.String("redisPassword", "", "")
)

func main() {
    flag.Parse()
    pool = newPool(*redisServer, *redisPassword)
    ...
}

A request handler gets a connection from the pool and closes the connection when the handler is done: 

func serveHome(w http.ResponseWriter, r *http.Request) {
    conn := pool.Get()
    defer conn.Close()
    ....
}

func NewPool 

func NewPool(newFn func() (Conn, error), maxIdle int) *Pool

NewPool creates a new pool. This function is deprecated. Applications should initialize the Pool fields directly as shown in example.

func (*Pool) ActiveCount 

func (p *Pool) ActiveCount() int

ActiveCount returns the number of active connections in the pool.

func (*Pool) Close 

func (p *Pool) Close() error

Close releases the resources used by the pool.

func (*Pool) Get 

func (p *Pool) Get() Conn

Get gets a connection. The application must close the returned connection. This method always returns a valid connection so that applications can defer error handling to the first use of the connection. If there is an error getting an underlying connection, then the connection Err, Do, Send, Flush and Receive methods return that error.

type PubSubConn 

type PubSubConn struct {
	Conn Conn
}

PubSubConn wraps a Conn with convenience methods for subscribers.

func (PubSubConn) Close 

func (c PubSubConn) Close() error

Close closes the connection.

func (PubSubConn) PSubscribe 

func (c PubSubConn) PSubscribe(channel ...interface{}) error

PSubscribe subscribes the connection to the given patterns.

func (PubSubConn) PUnsubscribe 

func (c PubSubConn) PUnsubscribe(channel ...interface{}) error

PUnsubscribe unsubscribes the connection from the given patterns, or from all of them if none is given.

func (PubSubConn) Receive 

func (c PubSubConn) Receive() interface{}

Receive returns a pushed message as a Subscription, Message, PMessage or error. The return value is intended to be used directly in a type switch as illustrated in the PubSubConn example.

func (PubSubConn) Subscribe 

func (c PubSubConn) Subscribe(channel ...interface{}) error

Subscribe subscribes the connection to the specified channels.

func (PubSubConn) Unsubscribe 

func (c PubSubConn) Unsubscribe(channel ...interface{}) error

Unsubscribe unsubscribes the connection from the given channels, or from all of them if none is given.

type Script 

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

Script encapsulates the source, hash and key count for a Lua script. See http://redis.io/commands/eval for information on scripts in Redis.

func NewScript 

func NewScript(keyCount int, src string) *Script

NewScript returns a new script object. If keyCount is greater than or equal to zero, then the count is automatically inserted in the EVAL command argument list. If keyCount is less than zero, then the application supplies the count as the first value in the keysAndArgs argument to the Do, Send and SendHash methods.

func (*Script) Do 

func (s *Script) Do(c Conn, keysAndArgs ...interface{}) (interface{}, error)

Do evaluates the script. Under the covers, Do optimistically evaluates the script using the EVALSHA command. If the command fails because the script is not loaded, then Do evaluates the script using the EVAL command (thus causing the script to load).

func (*Script) Load 

func (s *Script) Load(c Conn) error

Load loads the script without evaluating it.

func (*Script) Send 

func (s *Script) Send(c Conn, keysAndArgs ...interface{}) error

Send evaluates the script without waiting for the reply.

func (*Script) SendHash 

func (s *Script) SendHash(c Conn, keysAndArgs ...interface{}) error

SendHash evaluates the script without waiting for the reply. The script is evaluated with the EVALSHA command. The application must ensure that the script is loaded by a previous call to Send, Do or Load methods.

type Subscription 

type Subscription struct {

	// Kind is "subscribe", "unsubscribe", "psubscribe" or "punsubscribe"
	Kind string

	// The channel that was changed.
	Channel string

	// The current number of subscriptions for connection.
	Count int
}

Subscription represents a subscribe or unsubscribe notification.

Source Files

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