options.go

/*
 * Copyright (c) 2021 IBM Corp and others.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v2.0
 * and Eclipse Distribution License v1.0 which accompany this distribution.
 *
 * The Eclipse Public License is available at
 *    https://www.eclipse.org/legal/epl-2.0/
 * and the Eclipse Distribution License is available at
 *   http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * Contributors:
 *    Seth Hoenig
 *    Allan Stockdill-Mander
 *    Mike Robertson
 *    Måns Ansgariusson
 */

// Portions copyright © 2018 TIBCO Software Inc.

package mqtt

import (
	"crypto/tls"
	"net"
	"net/http"
	"net/url"
	"strings"
	"time"
)

// CredentialsProvider allows the username and password to be updated
// before reconnecting. It should return the current username and password.
type CredentialsProvider func() (username string, password string)

// MessageHandler is a callback type which can be set to be
// executed upon the arrival of messages published to topics
// to which the client is subscribed.
type MessageHandler func(Client, Message)

// ConnectionLostHandler is a callback type which can be set to be
// executed upon an unintended disconnection from the MQTT broker.
// Disconnects caused by calling Disconnect or ForceDisconnect will
// not cause an OnConnectionLost callback to execute.
type ConnectionLostHandler func(Client, error)

// OnConnectHandler is a callback that is called when the client
// state changes from unconnected/disconnected to connected. Both
// at initial connection and on reconnection
type OnConnectHandler func(Client, bool)

// ReconnectHandler is invoked prior to reconnecting after
// the initial connection is lost
type ReconnectHandler func(Client, *ClientOptions)

// ConnectionAttemptHandler is invoked prior to making the initial connection.
type ConnectionAttemptHandler func(broker *url.URL, tlsCfg *tls.Config) *tls.Config

// OpenConnectionFunc is invoked to establish the underlying network connection
// Its purpose if for custom network transports.
// Does not carry out any MQTT specific handshakes.
type OpenConnectionFunc func(uri *url.URL, options ClientOptions) (net.Conn, error)

// ClientOptions contains configurable options for an Client. Note that these should be set using the
// relevant methods (e.g. AddBroker) rather than directly. See those functions for information on usage.
// WARNING: Create the below using NewClientOptions unless you have a compelling reason not to. It is easy
// to create a configuration with difficult to trace issues (e.g. Mosquitto 2.0.12+ will reject connections
// with KeepAlive=0 by default).
type ClientOptions struct {
	Servers                 []*url.URL
	ClientID                string
	Username                string
	Password                string
	CredentialsProvider     CredentialsProvider
	CleanSession            bool
	Order                   bool
	WillEnabled             bool
	WillTopic               string
	WillPayload             []byte
	WillQos                 byte
	WillRetained            bool
	ProtocolVersion         uint
	protocolVersionExplicit bool
	TLSConfig               *tls.Config
	KeepAlive               int64 // Warning: Some brokers may reject connections with Keepalive = 0.
	PingTimeout             time.Duration
	ConnectTimeout          time.Duration
	MaxReconnectInterval    time.Duration
	AutoReconnect           bool
	ConnectRetryInterval    time.Duration
	ConnectRetry            bool
	Store                   Store
	DefaultPublishHandler   MessageHandler
	OnConnect               OnConnectHandler
	OnConnectionLost        ConnectionLostHandler
	OnReconnecting          ReconnectHandler
	OnConnectAttempt        ConnectionAttemptHandler
	WriteTimeout            time.Duration
	MessageChannelDepth     uint
	ResumeSubs              bool
	HTTPHeaders             http.Header
	WebsocketOptions        *WebsocketOptions
	MaxResumePubInFlight    int // // 0 = no limit; otherwise this is the maximum simultaneous messages sent while resuming
	Dialer                  *net.Dialer
	CustomOpenConnectionFn  OpenConnectionFunc
}

// NewClientOptions will create a new ClientClientOptions type with some
// default values.
//   Port: 1883
//   CleanSession: True
//   Order: True (note: it is recommended that this be set to FALSE unless order is important)
//   KeepAlive: 30 (seconds)
//   ConnectTimeout: 30 (seconds)
//   MaxReconnectInterval 10 (minutes)
//   AutoReconnect: True
func NewClientOptions() *ClientOptions {
	o := &ClientOptions{
		Servers:                 nil,
		ClientID:                "",
		Username:                "",
		Password:                "",
		CleanSession:            true,
		Order:                   true,
		WillEnabled:             false,
		WillTopic:               "",
		WillPayload:             nil,
		WillQos:                 0,
		WillRetained:            false,
		ProtocolVersion:         0,
		protocolVersionExplicit: false,
		KeepAlive:               30,
		PingTimeout:             10 * time.Second,
		ConnectTimeout:          30 * time.Second,
		MaxReconnectInterval:    10 * time.Minute,
		AutoReconnect:           true,
		ConnectRetryInterval:    30 * time.Second,
		ConnectRetry:            false,
		Store:                   nil,
		OnConnect:               nil,
		OnConnectionLost:        DefaultConnectionLostHandler,
		OnConnectAttempt:        nil,
		WriteTimeout:            0, // 0 represents timeout disabled
		ResumeSubs:              false,
		HTTPHeaders:             make(map[string][]string),
		WebsocketOptions:        &WebsocketOptions{},
		Dialer:                  &net.Dialer{Timeout: 30 * time.Second},
		CustomOpenConnectionFn:  nil,
	}
	return o
}

// AddBroker adds a broker URI to the list of brokers to be used. The format should be
// scheme://host:port
// Where "scheme" is one of "tcp", "ssl", or "ws", "host" is the ip-address (or hostname)
// and "port" is the port on which the broker is accepting connections.
//
// Default values for hostname is "127.0.0.1", for schema is "tcp://".
//
// An example broker URI would look like: tcp://foobar.com:1883
func (o *ClientOptions) AddBroker(server string) *ClientOptions {
	if len(server) > 0 && server[0] == ':' {
		server = "127.0.0.1" + server
	}
	if !strings.Contains(server, "://") {
		server = "tcp://" + server
	}
	brokerURI, err := url.Parse(server)
	if err != nil {
		ERROR.Println(CLI, "Failed to parse %q broker address: %s", server, err)
		return o
	}
	o.Servers = append(o.Servers, brokerURI)
	return o
}

// SetResumeSubs will enable resuming of stored (un)subscribe messages when connecting
// but not reconnecting if CleanSession is false. Otherwise these messages are discarded.
func (o *ClientOptions) SetResumeSubs(resume bool) *ClientOptions {
	o.ResumeSubs = resume
	return o
}

// SetClientID will set the client id to be used by this client when
// connecting to the MQTT broker. According to the MQTT v3.1 specification,
// a client id must be no longer than 23 characters.
func (o *ClientOptions) SetClientID(id string) *ClientOptions {
	o.ClientID = id
	return o
}

// SetUsername will set the username to be used by this client when connecting
// to the MQTT broker. Note: without the use of SSL/TLS, this information will
// be sent in plaintext across the wire.
func (o *ClientOptions) SetUsername(u string) *ClientOptions {
	o.Username = u
	return o
}

// SetPassword will set the password to be used by this client when connecting
// to the MQTT broker. Note: without the use of SSL/TLS, this information will
// be sent in plaintext across the wire.
func (o *ClientOptions) SetPassword(p string) *ClientOptions {
	o.Password = p
	return o
}

// SetCredentialsProvider will set a method to be called by this client when
// connecting to the MQTT broker that provide the current username and password.
// Note: without the use of SSL/TLS, this information will be sent
// in plaintext across the wire.
func (o *ClientOptions) SetCredentialsProvider(p CredentialsProvider) *ClientOptions {
	o.CredentialsProvider = p
	return o
}

// SetCleanSession will set the "clean session" flag in the connect message
// when this client connects to an MQTT broker. By setting this flag, you are
// indicating that no messages saved by the broker for this client should be
// delivered. Any messages that were going to be sent by this client before
// disconnecting previously but didn't will not be sent upon connecting to the
// broker.
func (o *ClientOptions) SetCleanSession(clean bool) *ClientOptions {
	o.CleanSession = clean
	return o
}

// SetOrderMatters will set the message routing to guarantee order within
// each QoS level. By default, this value is true. If set to false (recommended),
// this flag indicates that messages can be delivered asynchronously
// from the client to the application and possibly arrive out of order.
// Specifically, the message handler is called in its own go routine.
// Note that setting this to true does not guarantee in-order delivery
// (this is subject to broker settings like "max_inflight_messages=1" in mosquitto)
// and if true then handlers must not block.
func (o *ClientOptions) SetOrderMatters(order bool) *ClientOptions {
	o.Order = order
	return o
}

// SetTLSConfig will set an SSL/TLS configuration to be used when connecting
// to an MQTT broker. Please read the official Go documentation for more
// information.
func (o *ClientOptions) SetTLSConfig(t *tls.Config) *ClientOptions {
	o.TLSConfig = t
	return o
}

// SetStore will set the implementation of the Store interface
// used to provide message persistence in cases where QoS levels
// QoS_ONE or QoS_TWO are used. If no store is provided, then the
// client will use MemoryStore by default.
func (o *ClientOptions) SetStore(s Store) *ClientOptions {
	o.Store = s
	return o
}

// SetKeepAlive will set the amount of time (in seconds) that the client
// should wait before sending a PING request to the broker. This will
// allow the client to know that a connection has not been lost with the
// server.
func (o *ClientOptions) SetKeepAlive(k time.Duration) *ClientOptions {
	o.KeepAlive = int64(k / time.Second)
	return o
}

// SetPingTimeout will set the amount of time (in seconds) that the client
// will wait after sending a PING request to the broker, before deciding
// that the connection has been lost. Default is 10 seconds.
func (o *ClientOptions) SetPingTimeout(k time.Duration) *ClientOptions {
	o.PingTimeout = k
	return o
}

// SetProtocolVersion sets the MQTT version to be used to connect to the
// broker. Legitimate values are currently 3 - MQTT 3.1 or 4 - MQTT 3.1.1
func (o *ClientOptions) SetProtocolVersion(pv uint) *ClientOptions {
	if (pv >= 3 && pv <= 4) || (pv > 0x80) {
		o.ProtocolVersion = pv
		o.protocolVersionExplicit = true
	}
	return o
}

// UnsetWill will cause any set will message to be disregarded.
func (o *ClientOptions) UnsetWill() *ClientOptions {
	o.WillEnabled = false
	return o
}

// SetWill accepts a string will message to be set. When the client connects,
// it will give this will message to the broker, which will then publish the
// provided payload (the will) to any clients that are subscribed to the provided
// topic.
func (o *ClientOptions) SetWill(topic string, payload string, qos byte, retained bool) *ClientOptions {
	o.SetBinaryWill(topic, []byte(payload), qos, retained)
	return o
}

// SetBinaryWill accepts a []byte will message to be set. When the client connects,
// it will give this will message to the broker, which will then publish the
// provided payload (the will) to any clients that are subscribed to the provided
// topic.
func (o *ClientOptions) SetBinaryWill(topic string, payload []byte, qos byte, retained bool) *ClientOptions {
	o.WillEnabled = true
	o.WillTopic = topic
	o.WillPayload = payload
	o.WillQos = qos
	o.WillRetained = retained
	return o
}

// SetDefaultPublishHandler sets the MessageHandler that will be called when a message
// is received that does not match any known subscriptions.
//
// If OrderMatters is true (the defaultHandler) then callback must not block or
// call functions within this package that may block (e.g. Publish) other than in
// a new go routine.
// defaultHandler must be safe for concurrent use by multiple goroutines.
func (o *ClientOptions) SetDefaultPublishHandler(defaultHandler MessageHandler) *ClientOptions {
	o.DefaultPublishHandler = defaultHandler
	return o
}

// SetOnConnectHandler sets the function to be called when the client is connected. Both
// at initial connection time and upon automatic reconnect.
func (o *ClientOptions) SetOnConnectHandler(onConn OnConnectHandler) *ClientOptions {
	o.OnConnect = onConn
	return o
}

// SetConnectionLostHandler will set the OnConnectionLost callback to be executed
// in the case where the client unexpectedly loses connection with the MQTT broker.
func (o *ClientOptions) SetConnectionLostHandler(onLost ConnectionLostHandler) *ClientOptions {
	o.OnConnectionLost = onLost
	return o
}

// SetReconnectingHandler sets the OnReconnecting callback to be executed prior
// to the client attempting a reconnect to the MQTT broker.
func (o *ClientOptions) SetReconnectingHandler(cb ReconnectHandler) *ClientOptions {
	o.OnReconnecting = cb
	return o
}

// SetConnectionAttemptHandler sets the ConnectionAttemptHandler callback to be executed prior
// to each attempt to connect to an MQTT broker. Returns the *tls.Config that will be used when establishing
// the connection (a copy of the tls.Config from ClientOptions will be passed in along with the broker URL).
// This allows connection specific changes to be made to the *tls.Config.
func (o *ClientOptions) SetConnectionAttemptHandler(onConnectAttempt ConnectionAttemptHandler) *ClientOptions {
	o.OnConnectAttempt = onConnectAttempt
	return o
}

// SetWriteTimeout puts a limit on how long a mqtt publish should block until it unblocks with a
// timeout error. A duration of 0 never times out. Default never times out
func (o *ClientOptions) SetWriteTimeout(t time.Duration) *ClientOptions {
	o.WriteTimeout = t
	return o
}

// SetConnectTimeout limits how long the client will wait when trying to open a connection
// to an MQTT server before timing out. A duration of 0 never times out.
// Default 30 seconds. Currently only operational on TCP/TLS connections.
func (o *ClientOptions) SetConnectTimeout(t time.Duration) *ClientOptions {
	o.ConnectTimeout = t
	o.Dialer.Timeout = t
	return o
}

// SetMaxReconnectInterval sets the maximum time that will be waited between reconnection attempts
// when connection is lost
func (o *ClientOptions) SetMaxReconnectInterval(t time.Duration) *ClientOptions {
	o.MaxReconnectInterval = t
	return o
}

// SetAutoReconnect sets whether the automatic reconnection logic should be used
// when the connection is lost, even if disabled the ConnectionLostHandler is still
// called
func (o *ClientOptions) SetAutoReconnect(a bool) *ClientOptions {
	o.AutoReconnect = a
	return o
}

// SetConnectRetryInterval sets the time that will be waited between connection attempts
// when initially connecting if ConnectRetry is TRUE
func (o *ClientOptions) SetConnectRetryInterval(t time.Duration) *ClientOptions {
	o.ConnectRetryInterval = t
	return o
}

// SetConnectRetry sets whether the connect function will automatically retry the connection
// in the event of a failure (when true the token returned by the Connect function will
// not complete until the connection is up or it is cancelled)
// If ConnectRetry is true then subscriptions should be requested in OnConnect handler
// Setting this to TRUE permits messages to be published before the connection is established
func (o *ClientOptions) SetConnectRetry(a bool) *ClientOptions {
	o.ConnectRetry = a
	return o
}

// SetMessageChannelDepth DEPRECATED The value set here no longer has any effect, this function
// remains so the API is not altered.
func (o *ClientOptions) SetMessageChannelDepth(s uint) *ClientOptions {
	o.MessageChannelDepth = s
	return o
}

// SetHTTPHeaders sets the additional HTTP headers that will be sent in the WebSocket
// opening handshake.
func (o *ClientOptions) SetHTTPHeaders(h http.Header) *ClientOptions {
	o.HTTPHeaders = h
	return o
}

// SetWebsocketOptions sets the additional websocket options used in a WebSocket connection
func (o *ClientOptions) SetWebsocketOptions(w *WebsocketOptions) *ClientOptions {
	o.WebsocketOptions = w
	return o
}

// SetMaxResumePubInFlight sets the maximum simultaneous publish messages that will be sent while resuming. Note that
// this only applies to messages coming from the store (so additional sends may push us over the limit)
// Note that the connect token will not be flagged as complete until all messages have been sent from the
// store. If broker does not respond to messages then resume may not complete.
// This option was put in place because resuming after downtime can saturate low capacity links.
func (o *ClientOptions) SetMaxResumePubInFlight(MaxResumePubInFlight int) *ClientOptions {
	o.MaxResumePubInFlight = MaxResumePubInFlight
	return o
}

// SetDialer sets the tcp dialer options used in a tcp connection
func (o *ClientOptions) SetDialer(dialer *net.Dialer) *ClientOptions {
	o.Dialer = dialer
	return o
}

// SetCustomOpenConnectionFn replaces the inbuilt function that establishes a network connection with a custom function.
// The passed in function should return an open `net.Conn` or an error (see the existing openConnection function for an example)
// It enables custom networking types in addition to the defaults (tcp, tls, websockets...)
func (o *ClientOptions) SetCustomOpenConnectionFn(customOpenConnectionFn OpenConnectionFunc) *ClientOptions {
	if customOpenConnectionFn != nil {
		o.CustomOpenConnectionFn = customOpenConnectionFn
	}
	return o
}