nats.go – github.com/nats-io/nats.go Index | Examples | Files | Directories

package nats

import "github.com/nats-io/nats.go"

A Go client for the NATS messaging system (https://nats.io).

A Go client for the NATS messaging system (https://nats.io).

Index

Examples

Constants 

const (
	JSON_ENCODER    = "json"
	GOB_ENCODER     = "gob"
	DEFAULT_ENCODER = "default"
)

Indexe names into the Registered Encoders. 

const (
	Version                 = "1.3.1"
	DefaultURL              = "nats://localhost:4222"
	DefaultPort             = 4222
	DefaultMaxReconnect     = 60
	DefaultReconnectWait    = 2 * time.Second
	DefaultTimeout          = 2 * time.Second
	DefaultPingInterval     = 2 * time.Minute
	DefaultMaxPingOut       = 2
	DefaultMaxChanLen       = 8192            // 8k
	DefaultReconnectBufSize = 8 * 1024 * 1024 // 8MB
	RequestChanLen          = 8
	LangString              = "go"
)

Default Constants 

const (
	DISCONNECTED = Status(iota)
	CONNECTED
	CLOSED
	RECONNECTING
	CONNECTING
)
const (
	AsyncSubscription = SubscriptionType(iota)
	SyncSubscription
	ChanSubscription
	NilSubscription
)

The different types of subscription types. 

const (
	DefaultSubPendingMsgsLimit  = 65536
	DefaultSubPendingBytesLimit = 65536 * 1024
)

Pending Limits 

const (
	OP_START = iota
	OP_PLUS
	OP_PLUS_O
	OP_PLUS_OK
	OP_MINUS
	OP_MINUS_E
	OP_MINUS_ER
	OP_MINUS_ERR
	OP_MINUS_ERR_SPC
	MINUS_ERR_ARG
	OP_M
	OP_MS
	OP_MSG
	OP_MSG_SPC
	MSG_ARG
	MSG_PAYLOAD
	MSG_END
	OP_P
	OP_PI
	OP_PIN
	OP_PING
	OP_PO
	OP_PON
	OP_PONG
	OP_I
	OP_IN
	OP_INF
	OP_INFO
	OP_INFO_SPC
	INFO_ARG
)
const AUTHORIZATION_ERR = "authorization violation"

AUTHORIZATION_ERR is for when nats server user authorization has failed. 

const InboxPrefix = "_INBOX."

InboxPrefix is the prefix for all inbox subjects. 

const MAX_CONTROL_LINE_SIZE = 1024
const PERMISSIONS_ERR = "permissions violation"

PERMISSIONS_ERR is for when nats server subject authorization has failed. 

const STALE_CONNECTION = "stale connection"

STALE_CONNECTION is for detection and proper handling of stale connections.

Variables 

var (
	ErrConnectionClosed     = errors.New("nats: connection closed")
	ErrSecureConnRequired   = errors.New("nats: secure connection required")
	ErrSecureConnWanted     = errors.New("nats: secure connection not available")
	ErrBadSubscription      = errors.New("nats: invalid subscription")
	ErrTypeSubscription     = errors.New("nats: invalid subscription type")
	ErrBadSubject           = errors.New("nats: invalid subject")
	ErrSlowConsumer         = errors.New("nats: slow consumer, messages dropped")
	ErrTimeout              = errors.New("nats: timeout")
	ErrBadTimeout           = errors.New("nats: timeout invalid")
	ErrAuthorization        = errors.New("nats: authorization violation")
	ErrNoServers            = errors.New("nats: no servers available for connection")
	ErrJsonParse            = errors.New("nats: connect message, json parse error")
	ErrChanArg              = errors.New("nats: argument needs to be a channel type")
	ErrMaxPayload           = errors.New("nats: maximum payload exceeded")
	ErrMaxMessages          = errors.New("nats: maximum messages delivered")
	ErrSyncSubRequired      = errors.New("nats: illegal call on an async subscription")
	ErrMultipleTLSConfigs   = errors.New("nats: multiple tls.Configs not allowed")
	ErrNoInfoReceived       = errors.New("nats: protocol exception, INFO not received")
	ErrReconnectBufExceeded = errors.New("nats: outbound buffer limit exceeded")
	ErrInvalidConnection    = errors.New("nats: invalid connection")
	ErrInvalidMsg           = errors.New("nats: invalid message or message nil")
	ErrInvalidArg           = errors.New("nats: invalid argument")
	ErrInvalidContext       = errors.New("nats: invalid context")
	ErrStaleConnection      = errors.New("nats: " + STALE_CONNECTION)
)

Errors 

var DefaultOptions = GetDefaultOptions()

DEPRECATED: Use GetDefaultOptions() instead. DefaultOptions is not safe for use by multiple clients. For details see #308.

Functions

func NewInbox 

func NewInbox() string

NewInbox will return an inbox string which can be used for directed replies from subscribers. These are guaranteed to be unique, but can be shared and subscribed to by others.

func RegisterEncoder 

func RegisterEncoder(encType string, enc Encoder)

RegisterEncoder will register the encType with the given Encoder. Useful for customization.

Types

type Conn 

type Conn struct {
	// Keep all members for which we use atomic at the beginning of the
	// struct and make sure they are all 64bits (or use padding if necessary).
	// atomic.* functions crash on 32bit machines if operand is not aligned
	// at 64bit. See https://github.com/golang/go/issues/599
	Statistics

	Opts Options
	// contains filtered or unexported fields
}

A Conn represents a bare connection to a nats-server. It can send and receive []byte payloads.

func Connect 

func Connect(url string, options ...Option) (*Conn, error)

Connect will attempt to connect to the NATS system. The url can contain username/password semantics. e.g. nats://derek:pass@localhost:4222 Comma separated arrays are also supported, e.g. urlA, urlB. Options start with the defaults but can be overridden.

Example

Shows different ways to create a Conn

Code: 

{

	nc, _ := nats.Connect(nats.DefaultURL)
	nc.Close()

	nc, _ = nats.Connect("nats://derek:secretpassword@demo.nats.io:4222")
	nc.Close()

	nc, _ = nats.Connect("tls://derek:secretpassword@demo.nats.io:4443")
	nc.Close()

	opts := nats.Options{
		AllowReconnect: true,
		MaxReconnect:   10,
		ReconnectWait:  5 * time.Second,
		Timeout:        1 * time.Second,
	}

	nc, _ = opts.Connect()
	nc.Close()
}

func (*Conn) AuthRequired 

func (nc *Conn) AuthRequired() bool

AuthRequired will return if the connected server requires authorization.

func (*Conn) Buffered 

func (nc *Conn) Buffered() (int, error)

Buffered will return the number of bytes buffered to be sent to the server. FIXME(dlc) take into account disconnected state.

func (*Conn) ChanQueueSubscribe 

func (nc *Conn) ChanQueueSubscribe(subj, group string, ch chan *Msg) (*Subscription, error)

ChanQueueSubscribe will place all messages received on the channel. You should not close the channel until sub.Unsubscribe() has been called.

func (*Conn) ChanSubscribe 

func (nc *Conn) ChanSubscribe(subj string, ch chan *Msg) (*Subscription, error)

ChanSubscribe will place all messages received on the channel. You should not close the channel until sub.Unsubscribe() has been called.

func (*Conn) Close 

func (nc *Conn) Close()

Close will close the connection to the server. This call will release all blocking calls, such as Flush() and NextMsg()

Example

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	nc.Close()
}

func (*Conn) ConnectedServerId 

func (nc *Conn) ConnectedServerId() string

Report the connected server's Id

func (*Conn) ConnectedUrl 

func (nc *Conn) ConnectedUrl() string

Report the connected server's Url

func (*Conn) DiscoveredServers 

func (nc *Conn) DiscoveredServers() []string

DiscoveredServers returns only the server urls that have been discovered after a connection has been established. If authentication is enabled, use UserInfo or Token when connecting with these urls.

func (*Conn) Flush 

func (nc *Conn) Flush() error

Flush will perform a round trip to the server and return when it receives the internal reply.

Example

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	defer nc.Close()

	msg := &nats.Msg{Subject: "foo", Reply: "bar", Data: []byte("Hello World!")}
	for i := 0; i < 1000; i++ {
		nc.PublishMsg(msg)
	}
	err := nc.Flush()
	if err == nil {
		// Everything has been processed by the server for nc *Conn.
	}
}

func (*Conn) FlushTimeout 

func (nc *Conn) FlushTimeout(timeout time.Duration) (err error)

FlushTimeout allows a Flush operation to have an associated timeout.

Example

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	defer nc.Close()

	msg := &nats.Msg{Subject: "foo", Reply: "bar", Data: []byte("Hello World!")}
	for i := 0; i < 1000; i++ {
		nc.PublishMsg(msg)
	}
	// Only wait for up to 1 second for Flush
	err := nc.FlushTimeout(1 * time.Second)
	if err == nil {
		// Everything has been processed by the server for nc *Conn.
	}
}

func (*Conn) IsClosed 

func (nc *Conn) IsClosed() bool

IsClosed tests if a Conn has been closed.

func (*Conn) IsConnected 

func (nc *Conn) IsConnected() bool

IsConnected tests if a Conn is connected.

func (*Conn) IsReconnecting 

func (nc *Conn) IsReconnecting() bool

IsReconnecting tests if a Conn is reconnecting.

func (*Conn) LastError 

func (nc *Conn) LastError() error

LastError reports the last error encountered via the connection. It can be used reliably within ClosedCB in order to find out reason why connection was closed for example.

func (*Conn) MaxPayload 

func (nc *Conn) MaxPayload() int64

MaxPayload returns the size limit that a message payload can have. This is set by the server configuration and delivered to the client upon connect.

func (*Conn) Publish 

func (nc *Conn) Publish(subj string, data []byte) error

Publish publishes the data argument to the given subject. The data argument is left untouched and needs to be correctly interpreted on the receiver.

Example

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	defer nc.Close()

	nc.Publish("foo", []byte("Hello World!"))
}

func (*Conn) PublishMsg 

func (nc *Conn) PublishMsg(m *Msg) error

PublishMsg publishes the Msg structure, which includes the Subject, an optional Reply and an optional Data field.

Example

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	defer nc.Close()

	msg := &nats.Msg{Subject: "foo", Reply: "bar", Data: []byte("Hello World!")}
	nc.PublishMsg(msg)
}

func (*Conn) PublishRequest 

func (nc *Conn) PublishRequest(subj, reply string, data []byte) error

PublishRequest will perform a Publish() excpecting a response on the reply subject. Use Request() for automatically waiting for a response inline.

func (*Conn) QueueSubscribe 

func (nc *Conn) QueueSubscribe(subj, queue string, cb MsgHandler) (*Subscription, error)

QueueSubscribe creates an asynchronous queue subscriber on the given subject. All subscribers with the same queue name will form the queue group and only one member of the group will be selected to receive any given message asynchronously.

Example

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	defer nc.Close()

	received := 0

	nc.QueueSubscribe("foo", "worker_group", func(_ *nats.Msg) {
		received++
	})
}

func (*Conn) QueueSubscribeSync 

func (nc *Conn) QueueSubscribeSync(subj, queue string) (*Subscription, error)

QueueSubscribeSync creates a synchronous queue subscriber on the given subject. All subscribers with the same queue name will form the queue group and only one member of the group will be selected to receive any given message synchronously.

func (*Conn) QueueSubscribeSyncWithChan 

func (nc *Conn) QueueSubscribeSyncWithChan(subj, queue string, ch chan *Msg) (*Subscription, error)

QueueSubscribeSyncWithChan is syntactic sugar for ChanQueueSubscribe(subject, group, ch).

func (*Conn) Request 

func (nc *Conn) Request(subj string, data []byte, timeout time.Duration) (*Msg, error)

Request will send a request payload and deliver the response message, or an error, including a timeout if no message was received properly.

Example

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	defer nc.Close()

	nc.Subscribe("foo", func(m *nats.Msg) {
		nc.Publish(m.Reply, []byte("I will help you"))
	})
	nc.Request("foo", []byte("help"), 50*time.Millisecond)
}

func (*Conn) RequestWithContext 

func (nc *Conn) RequestWithContext(ctx context.Context, subj string, data []byte) (*Msg, error)

RequestWithContext takes a context, a subject and payload in bytes and request expecting a single response.

func (*Conn) Servers 

func (nc *Conn) Servers() []string

Servers returns the list of known server urls, including additional servers discovered after a connection has been established. If authentication is enabled, use UserInfo or Token when connecting with these urls.

func (*Conn) SetClosedHandler 

func (nc *Conn) SetClosedHandler(cb ConnHandler)

SetClosedHandler will set the reconnect event handler.

func (*Conn) SetDisconnectHandler 

func (nc *Conn) SetDisconnectHandler(dcb ConnHandler)

SetDisconnectHandler will set the disconnect event handler.

func (*Conn) SetDiscoveredServersHandler 

func (nc *Conn) SetDiscoveredServersHandler(dscb ConnHandler)

SetDiscoveredServersHandler will set the discovered servers handler.

func (*Conn) SetErrorHandler 

func (nc *Conn) SetErrorHandler(cb ErrHandler)

SetErrHandler will set the async error handler.

func (*Conn) SetReconnectHandler 

func (nc *Conn) SetReconnectHandler(rcb ConnHandler)

SetReconnectHandler will set the reconnect event handler.

func (*Conn) Stats 

func (nc *Conn) Stats() Statistics

Stats will return a race safe copy of the Statistics section for the connection.

func (*Conn) Status 

func (nc *Conn) Status() Status

Status returns the current state of the connection.

func (*Conn) Subscribe 

func (nc *Conn) Subscribe(subj string, cb MsgHandler) (*Subscription, error)

Subscribe will express interest in the given subject. The subject can have wildcards (partial:*, full:>). Messages will be delivered to the associated MsgHandler. If no MsgHandler is given, the subscription is a synchronous subscription and can be polled via Subscription.NextMsg().

Example

This Example shows an asynchronous subscriber.

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	defer nc.Close()

	nc.Subscribe("foo", func(m *nats.Msg) {
		fmt.Printf("Received a message: %s\n", string(m.Data))
	})
}

func (*Conn) SubscribeSync 

func (nc *Conn) SubscribeSync(subj string) (*Subscription, error)

SubscribeSync is syntactic sugar for Subscribe(subject, nil).

Example

This Example shows a synchronous subscriber.

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	defer nc.Close()

	sub, _ := nc.SubscribeSync("foo")
	m, err := sub.NextMsg(1 * time.Second)
	if err == nil {
		fmt.Printf("Received a message: %s\n", string(m.Data))
	} else {
		fmt.Println("NextMsg timed out.")
	}
}

func (*Conn) TLSRequired 

func (nc *Conn) TLSRequired() bool

TLSRequired will return if the connected server requires TLS connections.

type ConnHandler 

type ConnHandler func(*Conn)

ConnHandler is used for asynchronous events such as disconnected and closed connections.

type CustomDialer 

type CustomDialer interface {
	Dial(network, address string) (net.Conn, error)
}

CustomDialer can be used to specify any dialer, not necessarily a *net.Dialer.

type EncodedConn 

type EncodedConn struct {
	Conn *Conn
	Enc  Encoder
}

EncodedConn are the preferred way to interface with NATS. They wrap a bare connection to a nats server and have an extendable encoder system that will encode and decode messages from raw Go types.

func NewEncodedConn 

func NewEncodedConn(c *Conn, encType string) (*EncodedConn, error)

NewEncodedConn will wrap an existing Connection and utilize the appropriate registered encoder.

Example

Shows how to wrap a Conn into an EncodedConn

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	c, _ := nats.NewEncodedConn(nc, "json")
	c.Close()
}

func (*EncodedConn) BindRecvChan 

func (c *EncodedConn) BindRecvChan(subject string, channel interface{}) (*Subscription, error)

BindRecvChan binds a channel for receive operations from NATS.

Example

BindRecvChan() allows binding of a Go channel to a nats subject for subscribe operations. The Encoder attached to the EncodedConn will be used for un-marshaling.

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	c, _ := nats.NewEncodedConn(nc, "json")
	defer c.Close()

	type person struct {
		Name    string
		Address string
		Age     int
	}

	ch := make(chan *person)
	c.BindRecvChan("hello", ch)

	me := &person{Name: "derek", Age: 22, Address: "85 Second St"}
	c.Publish("hello", me)

	// Receive the publish directly on a channel
	who := <-ch

	fmt.Printf("%v says hello!\n", who)
}

func (*EncodedConn) BindRecvQueueChan 

func (c *EncodedConn) BindRecvQueueChan(subject, queue string, channel interface{}) (*Subscription, error)

BindRecvQueueChan binds a channel for queue-based receive operations from NATS.

func (*EncodedConn) BindSendChan 

func (c *EncodedConn) BindSendChan(subject string, channel interface{}) error

BindSendChan binds a channel for send operations to NATS.

Example

BindSendChan() allows binding of a Go channel to a nats subject for publish operations. The Encoder attached to the EncodedConn will be used for marshaling.

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	c, _ := nats.NewEncodedConn(nc, "json")
	defer c.Close()

	type person struct {
		Name    string
		Address string
		Age     int
	}

	ch := make(chan *person)
	c.BindSendChan("hello", ch)

	me := &person{Name: "derek", Age: 22, Address: "85 Second St"}
	ch <- me
}

func (*EncodedConn) Close 

func (c *EncodedConn) Close()

Close will close the connection to the server. This call will release all blocking calls, such as Flush(), etc.

func (*EncodedConn) Flush 

func (c *EncodedConn) Flush() error

Flush will perform a round trip to the server and return when it receives the internal reply.

func (*EncodedConn) FlushTimeout 

func (c *EncodedConn) FlushTimeout(timeout time.Duration) (err error)

FlushTimeout allows a Flush operation to have an associated timeout.

func (*EncodedConn) LastError 

func (c *EncodedConn) LastError() error

LastError reports the last error encountered via the Connection.

func (*EncodedConn) Publish 

func (c *EncodedConn) Publish(subject string, v interface{}) error

Publish publishes the data argument to the given subject. The data argument will be encoded using the associated encoder.

Example

EncodedConn can publish virtually anything just by passing it in. The encoder will be used to properly encode the raw Go type

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	c, _ := nats.NewEncodedConn(nc, "json")
	defer c.Close()

	type person struct {
		Name    string
		Address string
		Age     int
	}

	me := &person{Name: "derek", Age: 22, Address: "85 Second St"}
	c.Publish("hello", me)
}

func (*EncodedConn) PublishRequest 

func (c *EncodedConn) PublishRequest(subject, reply string, v interface{}) error

PublishRequest will perform a Publish() expecting a response on the reply subject. Use Request() for automatically waiting for a response inline.

func (*EncodedConn) QueueSubscribe 

func (c *EncodedConn) QueueSubscribe(subject, queue string, cb Handler) (*Subscription, error)

QueueSubscribe will create a queue subscription on the given subject and process incoming messages using the specified Handler. The Handler should be a func that matches a signature from the description of Handler from above.

func (*EncodedConn) Request 

func (c *EncodedConn) Request(subject string, v interface{}, vPtr interface{}, timeout time.Duration) error

Request will create an Inbox and perform a Request() call with the Inbox reply for the data v. A response will be decoded into the vPtrResponse.

func (*EncodedConn) RequestWithContext 

func (c *EncodedConn) RequestWithContext(ctx context.Context, subject string, v interface{}, vPtr interface{}) error

RequestWithContext will create an Inbox and perform a Request using the provided cancellation context with the Inbox reply for the data v. A response will be decoded into the vPtrResponse.

func (*EncodedConn) Subscribe 

func (c *EncodedConn) Subscribe(subject string, cb Handler) (*Subscription, error)

Subscribe will create a subscription on the given subject and process incoming messages using the specified Handler. The Handler should be a func that matches a signature from the description of Handler from above.

Example

EncodedConn's subscribers will automatically decode the wire data into the requested Go type using the Decode() method of the registered Encoder. The callback signature can also vary to include additional data, such as subject and reply subjects.

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	c, _ := nats.NewEncodedConn(nc, "json")
	defer c.Close()

	type person struct {
		Name    string
		Address string
		Age     int
	}

	c.Subscribe("hello", func(p *person) {
		fmt.Printf("Received a person! %+v\n", p)
	})

	c.Subscribe("hello", func(subj, reply string, p *person) {
		fmt.Printf("Received a person on subject %s! %+v\n", subj, p)
	})

	me := &person{Name: "derek", Age: 22, Address: "85 Second St"}
	c.Publish("hello", me)
}

type Encoder 

type Encoder interface {
	Encode(subject string, v interface{}) ([]byte, error)
	Decode(subject string, data []byte, vPtr interface{}) error
}

Encoder interface is for all register encoders

func EncoderForType 

func EncoderForType(encType string) Encoder

EncoderForType will return the registered Encoder for the encType.

type ErrHandler 

type ErrHandler func(*Conn, *Subscription, error)

ErrHandler is used to process asynchronous errors encountered while processing inbound messages.

type Handler 

type Handler interface{}

Handler is a specific callback used for Subscribe. It is generalized to an interface{}, but we will discover its format and arguments at runtime and perform the correct callback, including de-marshaling JSON strings back into the appropriate struct based on the signature of the Handler.

Handlers are expected to have one of four signatures. 

type person struct {
	Name string `json:"name,omitempty"`
	Age  uint   `json:"age,omitempty"`
}

handler := func(m *Msg)
handler := func(p *person)
handler := func(subject string, o *obj)
handler := func(subject, reply string, o *obj)

These forms allow a callback to request a raw Msg ptr, where the processing of the message from the wire is untouched. Process a JSON representation and demarshal it into the given struct, e.g. person. There are also variants where the callback wants either the subject, or the subject and the reply subject.

type Msg 

type Msg struct {
	Subject string
	Reply   string
	Data    []byte
	Sub     *Subscription
	// contains filtered or unexported fields
}

Msg is a structure used by Subscribers and PublishMsg().

type MsgHandler 

type MsgHandler func(msg *Msg)

MsgHandler is a callback function that processes messages delivered to asynchronous subscribers.

type Option 

type Option func(*Options) error

Option is a function on the options for a connection.

func ClientCert 

func ClientCert(certFile, keyFile string) Option

ClientCert is a helper option to provide the client certificate from a file. If Secure is not already set this will set it as well

func ClosedHandler 

func ClosedHandler(cb ConnHandler) Option

ClosedHandler is an Option to set the closed handler.

func Dialer 

func Dialer(dialer *net.Dialer) Option

Dialer is an Option to set the dialer which will be used when attempting to establish a connection. DEPRECATED: Should use CustomDialer instead.

func DisconnectHandler 

func DisconnectHandler(cb ConnHandler) Option

DisconnectHandler is an Option to set the disconnected handler.

func DiscoveredServersHandler 

func DiscoveredServersHandler(cb ConnHandler) Option

DiscoveredServersHandler is an Option to set the new servers handler.

func DontRandomize 

func DontRandomize() Option

DontRandomize is an Option to turn off randomizing the server pool.

func ErrorHandler 

func ErrorHandler(cb ErrHandler) Option

ErrHandler is an Option to set the async error handler.

func MaxReconnects 

func MaxReconnects(max int) Option

MaxReconnects is an Option to set the maximum number of reconnect attempts.

func Name 

func Name(name string) Option

Name is an Option to set the client name.

func NoReconnect 

func NoReconnect() Option

NoReconnect is an Option to turn off reconnect behavior.

func ReconnectHandler 

func ReconnectHandler(cb ConnHandler) Option

ReconnectHandler is an Option to set the reconnected handler.

func ReconnectWait 

func ReconnectWait(t time.Duration) Option

ReconnectWait is an Option to set the wait time between reconnect attempts.

func RootCAs 

func RootCAs(file ...string) Option

RootCAs is a helper option to provide the RootCAs pool from a list of filenames. If Secure is not already set this will set it as well.

func Secure 

func Secure(tls ...*tls.Config) Option

Secure is an Option to enable TLS secure connections that skip server verification by default. Pass a TLS Configuration for proper TLS.

func SetCustomDialer 

func SetCustomDialer(dialer CustomDialer) Option

SetCustomDialer is an Option to set a custom dialer which will be used when attempting to establish a connection. If both Dialer and CustomDialer are specified, CustomDialer takes precedence.

func Timeout 

func Timeout(t time.Duration) Option

Timeout is an Option to set the timeout for Dial on a connection.

func Token 

func Token(token string) Option

Token is an Option to set the token to use when not included directly in the URLs.

func UseOldRequestStyle 

func UseOldRequestStyle() Option

UseOldRequestyStyle is an Option to force usage of the old Request style.

func UserInfo 

func UserInfo(user, password string) Option

UserInfo is an Option to set the username and password to use when not included directly in the URLs.

type Options 

type Options struct {

	// Url represents a single NATS server url to which the client
	// will be connecting. If the Servers option is also set, it
	// then becomes the first server in the Servers array.
	Url string

	// Servers is a configured set of servers which this client
	// will use when attempting to connect.
	Servers []string

	// NoRandomize configures whether we will randomize the
	// server pool.
	NoRandomize bool

	// Name is an optional name label which will be sent to the server
	// on CONNECT to identify the client.
	Name string

	// Verbose signals the server to send an OK ack for commands
	// successfully processed by the server.
	Verbose bool

	// Pedantic signals the server whether it should be doing further
	// validation of subjects.
	Pedantic bool

	// Secure enables TLS secure connections that skip server
	// verification by default. NOT RECOMMENDED.
	Secure bool

	// TLSConfig is a custom TLS configuration to use for secure
	// transports.
	TLSConfig *tls.Config

	// AllowReconnect enables reconnection logic to be used when we
	// encounter a disconnect from the current server.
	AllowReconnect bool

	// MaxReconnect sets the number of reconnect attempts that will be
	// tried before giving up. If negative, then it will never give up
	// trying to reconnect.
	MaxReconnect int

	// ReconnectWait sets the time to backoff after attempting a reconnect
	// to a server that we were already connected to previously.
	ReconnectWait time.Duration

	// Timeout sets the timeout for a Dial operation on a connection.
	Timeout time.Duration

	// FlusherTimeout is the maximum time to wait for the flusher loop
	// to be able to finish writing to the underlying connection.
	FlusherTimeout time.Duration

	// PingInterval is the period at which the client will be sending ping
	// commands to the server, disabled if 0 or negative.
	PingInterval time.Duration

	// MaxPingsOut is the maximum number of pending ping commands that can
	// be awaiting a response before raising an ErrStaleConnection error.
	MaxPingsOut int

	// ClosedCB sets the closed handler that is called when a client will
	// no longer be connected.
	ClosedCB ConnHandler

	// DisconnectedCB sets the disconnected handler that is called
	// whenever the connection is disconnected.
	DisconnectedCB ConnHandler

	// ReconnectedCB sets the reconnected handler called whenever
	// the connection is successfully reconnected.
	ReconnectedCB ConnHandler

	// DiscoveredServersCB sets the callback that is invoked whenever a new
	// server has joined the cluster.
	DiscoveredServersCB ConnHandler

	// AsyncErrorCB sets the async error handler (e.g. slow consumer errors)
	AsyncErrorCB ErrHandler

	// ReconnectBufSize is the size of the backing bufio during reconnect.
	// Once this has been exhausted publish operations will return an error.
	ReconnectBufSize int

	// SubChanLen is the size of the buffered channel used between the socket
	// Go routine and the message delivery for SyncSubscriptions.
	// NOTE: This does not affect AsyncSubscriptions which are
	// dictated by PendingLimits()
	SubChanLen int

	// User sets the username to be used when connecting to the server.
	User string

	// Password sets the password to be used when connecting to a server.
	Password string

	// Token sets the token to be used when connecting to a server.
	Token string

	// Dialer allows a custom net.Dialer when forming connections.
	// DEPRECATED: should use CustomDialer instead.
	Dialer *net.Dialer

	// CustomDialer allows to specify a custom dialer (not necessarily
	// a *net.Dialer).
	CustomDialer CustomDialer

	// UseOldRequestStyle forces the old method of Requests that utilize
	// a new Inbox and a new Subscription for each request.
	UseOldRequestStyle bool
}

Options can be used to create a customized connection.

func GetDefaultOptions 

func GetDefaultOptions() Options

GetDefaultOptions returns default configuration options for the client.

func (Options) Connect 

func (o Options) Connect() (*Conn, error)

Connect will attempt to connect to a NATS server with multiple options.

type Statistics 

type Statistics struct {
	InMsgs     uint64
	OutMsgs    uint64
	InBytes    uint64
	OutBytes   uint64
	Reconnects uint64
}

Tracks various stats received and sent on this connection, including counts for messages and bytes.

type Status 

type Status int

Status represents the state of the connection.

type Subscription 

type Subscription struct {

	// Subject that represents this subscription. This can be different
	// than the received subject inside a Msg if this is a wildcard.
	Subject string

	// Optional queue group name. If present, all subscriptions with the
	// same name will form a distributed queue, and each message will
	// only be processed by one member of the group.
	Queue string
	// contains filtered or unexported fields
}

A Subscription represents interest in a given subject.

func (*Subscription) AutoUnsubscribe 

func (s *Subscription) AutoUnsubscribe(max int) error

AutoUnsubscribe will issue an automatic Unsubscribe that is processed by the server when max messages have been received. This can be useful when sending a request to an unknown number of subscribers. Request() uses this functionality.

Example

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	defer nc.Close()

	received, wanted, total := 0, 10, 100

	sub, _ := nc.Subscribe("foo", func(_ *nats.Msg) {
		received++
	})
	sub.AutoUnsubscribe(wanted)

	for i := 0; i < total; i++ {
		nc.Publish("foo", []byte("Hello"))
	}
	nc.Flush()

	fmt.Printf("Received = %d", received)
}

func (*Subscription) ClearMaxPending 

func (s *Subscription) ClearMaxPending() error

ClearMaxPending resets the maximums seen so far.

func (*Subscription) Delivered 

func (s *Subscription) Delivered() (int64, error)

Delivered returns the number of delivered messages for this subscription.

func (*Subscription) Dropped 

func (s *Subscription) Dropped() (int, error)

Dropped returns the number of known dropped messages for this subscription. This will correspond to messages dropped by violations of PendingLimits. If the server declares the connection a SlowConsumer, this number may not be valid.

func (*Subscription) IsValid 

func (s *Subscription) IsValid() bool

IsValid returns a boolean indicating whether the subscription is still active. This will return false if the subscription has already been closed.

func (*Subscription) MaxPending 

func (s *Subscription) MaxPending() (int, int, error)

MaxPending returns the maximum number of queued messages and queued bytes seen so far.

func (*Subscription) NextMsg 

func (s *Subscription) NextMsg(timeout time.Duration) (*Msg, error)

NextMsg will return the next message available to a synchronous subscriber or block until one is available. A timeout can be used to return when no message has been delivered.

Example

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	defer nc.Close()

	sub, _ := nc.SubscribeSync("foo")
	m, err := sub.NextMsg(1 * time.Second)
	if err == nil {
		fmt.Printf("Received a message: %s\n", string(m.Data))
	} else {
		fmt.Println("NextMsg timed out.")
	}
}

func (*Subscription) NextMsgWithContext 

func (s *Subscription) NextMsgWithContext(ctx context.Context) (*Msg, error)

NextMsgWithContext takes a context and returns the next message available to a synchronous subscriber, blocking until it is delivered or context gets canceled.

func (*Subscription) Pending 

func (s *Subscription) Pending() (int, int, error)

Pending returns the number of queued messages and queued bytes in the client for this subscription.

func (*Subscription) PendingLimits 

func (s *Subscription) PendingLimits() (int, int, error)

PendingLimits returns the current limits for this subscription. If no error is returned, a negative value indicates that the given metric is not limited.

func (*Subscription) QueuedMsgs 

func (s *Subscription) QueuedMsgs() (int, error)

Queued returns the number of queued messages in the client for this subscription. DEPRECATED: Use Pending()

func (*Subscription) SetPendingLimits 

func (s *Subscription) SetPendingLimits(msgLimit, bytesLimit int) error

SetPendingLimits sets the limits for pending msgs and bytes for this subscription. Zero is not allowed. Any negative value means that the given metric is not limited.

func (*Subscription) Type 

func (s *Subscription) Type() SubscriptionType

Type returns the type of Subscription.

func (*Subscription) Unsubscribe 

func (s *Subscription) Unsubscribe() error

Unsubscribe will remove interest in the given subject.

Example

Code: 

{
	nc, _ := nats.Connect(nats.DefaultURL)
	defer nc.Close()

	sub, _ := nc.SubscribeSync("foo")
	// ...
	sub.Unsubscribe()
}

type SubscriptionType 

type SubscriptionType int

SubscriptionType is the type of the Subscription.

Source Files

context.go enc.go nats.go netchan.go parser.go timer.go

Directories

PathSynopsis
bench
encoders
encoders/builtin
encoders/protobuf
examples
test
util
Version
v1.4.0
Published
Dec 20, 2017
Platform
js/wasm
Imports
22 packages
Last checked
now –

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