sentinel

Documentation

Overview

Package sentinel provides a convenient interface with a redis sentinel which will automatically handle pooling connections and automatic failover.

Here's an example of creating a sentinel client and then using it to perform some commands

func example() error {
	// If there exists sentinel masters "bucket0" and "bucket1", and we want
	// out client to create pools for both:
	client, err := sentinel.NewClient("tcp", "localhost:6379", 100, "bucket0", "bucket1")
	if err != nil {
		return err
	}

	if err := exampleCmd(client); err != nil {
		return err
	}

	return nil
}

func exampleCmd(client *sentinel.Client) error {
	conn, err := client.GetMaster("bucket0")
	if err != nil {
		return redisErr
	}
	defer client.PutMaster("bucket0", conn)

	i, err := conn.Cmd("GET", "foo").Int()
	if err != nil {
		return err
	}

	if err := conn.Cmd("SET", "foo", i+1); err != nil {
		return err
	}

	return nil
}

This package only guarantees that when GetMaster is called the returned connection will be a connection to the master as of the moment that method is called. It is still possible that there is a failover as that connection is being used by the application.

As a final note, a Client can be interacted with from multiple routines at once safely, except for the Close method. To safely Close, ensure that only one routine ever makes the call and that once the call is made no other methods are ever called by any routines.

Index

• type Client
  • func NewClient(network, address string, poolSize int, names ...string) (*Client, error)
  • func NewClientCustom(network, address string, poolSize int, df DialFunc, names ...string) (*Client, error)
  • func (c *Client) GetMaster(name string) (*redis.Client, error)
  • func (c *Client) PutMaster(name string, client *redis.Client)
• type ClientError
  • func (ce *ClientError) Error() string
• type DialFunc

Types

type Client

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

Client communicates with a sentinel instance and manages connection pools of active masters

func NewClient

func NewClient(
	network, address string, poolSize int, names ...string,
) (
	*Client, error,
)

NewClient creates a sentinel client. Connects to the given sentinel instance, pulls the information for the masters of the given names, and creates an initial pool of connections for each master. The client will automatically replace the pool for any master should sentinel decide to fail the master over. The returned error is a *ClientError.

func NewClientCustom

func NewClientCustom(
	network, address string, poolSize int, df DialFunc, names ...string,
) (
	*Client, error,
)

NewClientCustom is the same as NewClient, except it takes in a DialFunc which will be used to create all new connections to the master instances. This can be used to implement authentication, custom timeouts, etc...

func (*Client) GetMaster

func (c *Client) GetMaster(name string) (*redis.Client, error)

GetMaster retrieves a connection for the master of the given name. If sentinel has become unreachable this will always return an error. Close should be called in that case. The returned error is a *ClientError.

func (*Client) PutMaster

func (c *Client) PutMaster(name string, client *redis.Client)

PutMaster return a connection for a master of a given name

type ClientError

type ClientError struct {

	// If this is true the error is due to a problem with the sentinel
	// connection, either it being closed or otherwise unavailable. If false the
	// error is due to some other circumstances. This is useful if you want to
	// implement some kind of reconnecting to sentinel on an error.
	SentinelErr bool
	// contains filtered or unexported fields
}

ClientError is an error wrapper returned by operations in this package. It implements the error interface and can therefore be passed around as a normal error.

func (*ClientError) Error

func (ce *ClientError) Error() string

Error implements the error protocol

type DialFunc

type DialFunc func(network, addr string) (*redis.Client, error)

DialFunc is a function which can be passed into NewClientCustom