记录rabbitMq中Channel常见的方法

channel.exchangeDeclare()#

  • type:direct、fanout、topic
  • durable:(true、false) true:服务器重启会保留下来Exchange。警告:仅设置此选项,不代表消息持久化。即不保证重启后消息还在。

原文:true if we are declaring a durable exchange (the exchange will survive a server restart

  • autoDelete:(true、false) true:当已经没有消费者时,服务器是否可以删除该Exchange

原文:true if the server should delete the exchange when it is no longer in use

 /**
     * Declare an exchange.
     * @see com.rabbitmq.client.AMQP.Exchange.Declare
     * @see com.rabbitmq.client.AMQP.Exchange.DeclareOk
     * @param exchange the name of the exchange
     * @param type the exchange type
     * @param durable true if we are declaring a durable exchange (the exchange will survive a server restart)
     * @param autoDelete true if the server should delete the exchange when it is no longer in use
     * @param arguments other properties (construction arguments) for the exchange
     * @return a declaration-confirm method to indicate the exchange was successfully declared
     * @throws java.io.IOException if an error is encountered
     */
    Exchange.DeclareOk exchangeDeclare(String exchange, String type, boolean durable, boolean autoDelete,
                                       Map<String, Object> arguments) throws IOException;

chanel.basicQos()#

  • prefetchSize:0
  • prefetchCount:会告诉RabbitMQ不要同时给一个消费者推送多于N个消息,即一旦有N个消息还没有ack,则该consumer将block掉,直到有消息ack
  • globaltrue\false 是否将上面设置应用于channel,简单点说,就是上面限制是channel级别的还是consumer级别

备注:据说prefetchSize 和global这两项,rabbitmq没有实现,暂且不研究

    /**
     * Request specific "quality of service" settings.
     *
     * These settings impose limits on the amount of data the server
     * will deliver to consumers before requiring acknowledgements.
     * Thus they provide a means of consumer-initiated flow control.
     * @see com.rabbitmq.client.AMQP.Basic.Qos
     * @param prefetchSize maximum amount of content (measured in
     * octets) that the server will deliver, 0 if unlimited
     * @param prefetchCount maximum number of messages that the server
     * will deliver, 0 if unlimited
     * @param global true if the settings should be applied to the
     * entire channel rather than each consumer
     * @throws java.io.IOException if an error is encountered
     */
    void basicQos(int prefetchSize, int prefetchCount, boolean global) throws IOException;

channel.basicPublish()#

  • routingKey:路由键,#匹配0个或多个单词,*匹配一个单词,在topic exchange做消息转发用
  • mandatory:true:如果exchange根据自身类型和消息routeKey无法找到一个符合条件的queue,那么会调用basic.return方法将消息返还给生产者。false:出现上述情形broker会直接将消息扔掉
  • immediate:true:如果exchange在将消息route到queue(s)时发现对应的queue上没有消费者,那么这条消息不会放入队列中。当与消息routeKey关联的所有queue(一个或多个)都没有消费者时,该消息会通过basic.return方法返还给生产者。
  • BasicProperties :需要注意的是BasicProperties.deliveryMode,0:不持久化 1:持久化 这里指的是消息的持久化,配合channel(durable=true),queue(durable)可以实现,即使服务器宕机,消息仍然保留

简单来说:mandatory标志告诉服务器至少将该消息route到一个队列中,否则将消息返还给生产者;immediate标志告诉服务器如果该消息关联的queue上有消费者,则马上将消息投递给它,如果所有queue都没有消费者,直接把消息返还给生产者,不用将消息入队列等待消费者了

  /**
     * Publish a message.
     *
     * Publishing to a non-existent exchange will result in a channel-level
     * protocol exception, which closes the channel.
     *
     * Invocations of <code>Channel#basicPublish</code> will eventually block if a
     * <a href="http://www.rabbitmq.com/alarms.html">resource-driven alarm</a> is in effect.
     *
     * @see com.rabbitmq.client.AMQP.Basic.Publish
     * @see <a href="http://www.rabbitmq.com/alarms.html">Resource-driven alarms</a>.
     * @param exchange the exchange to publish the message to
     * @param routingKey the routing key
     * @param mandatory true if the 'mandatory' flag is to be set
     * @param immediate true if the 'immediate' flag is to be
     * set. Note that the RabbitMQ server does not support this flag.
     * @param props other properties for the message - routing headers etc
     * @param body the message body
     * @throws java.io.IOException if an error is encountered
     */
    void basicPublish(String exchange, String routingKey, boolean mandatory, boolean immediate, BasicProperties props, byte[] body)
            throws IOException;

channel.basicAck()#

  • deliveryTag:该消息的index
  • multiple:是否批量;true:将一次性ack所有小于deliveryTag的消息
    /**
     * Acknowledge one or several received
     * messages. Supply the deliveryTag from the {@link com.rabbitmq.client.AMQP.Basic.GetOk}
     * or {@link com.rabbitmq.client.AMQP.Basic.Deliver} method
     * containing the received message being acknowledged.
     * @see com.rabbitmq.client.AMQP.Basic.Ack
     * @param deliveryTag the tag from the received {@link com.rabbitmq.client.AMQP.Basic.GetOk} or {@link com.rabbitmq.client.AMQP.Basic.Deliver}
     * @param multiple true to acknowledge all messages up to and
     * including the supplied delivery tag; false to acknowledge just
     * the supplied delivery tag.
     * @throws java.io.IOException if an error is encountered
     */
    void basicAck(long deliveryTag, boolean multiple) throws IOException;

channel.basicNack(delivery.getEnvelope().getDeliveryTag(), false, true)#

  • deliveryTag:该消息的index
  • multiple:是否批量.true:将一次性拒绝所有小于deliveryTag的消息
  • requeue:被拒绝的是否重新入队列
    /**
     * Reject one or several received messages.
     *
     * Supply the <code>deliveryTag</code> from the {@link com.rabbitmq.client.AMQP.Basic.GetOk}
     * or {@link com.rabbitmq.client.AMQP.Basic.GetOk} method containing the message to be rejected.
     * @see com.rabbitmq.client.AMQP.Basic.Nack
     * @param deliveryTag the tag from the received {@link com.rabbitmq.client.AMQP.Basic.GetOk} or {@link com.rabbitmq.client.AMQP.Basic.Deliver}
     * @param multiple true to reject all messages up to and including
     * the supplied delivery tag; false to reject just the supplied
     * delivery tag.
     * @param requeue true if the rejected message(s) should be requeued rather
     * than discarded/dead-lettered
     * @throws java.io.IOException if an error is encountered
     */
    void basicNack(long deliveryTag, boolean multiple, boolean requeue)
            throws IOException;

channel.basicReject(delivery.getEnvelope().getDeliveryTag(), false)#

  • deliveryTag:该消息的index
  • requeue:被拒绝的是否重新入队列

channel.basicNack 与 channel.basicReject 的区别在于basicNack可以拒绝多条消息,而basicReject一次只能拒绝一条消息

 /**
     * Reject a message. Supply the deliveryTag from the {@link com.rabbitmq.client.AMQP.Basic.GetOk}
     * or {@link com.rabbitmq.client.AMQP.Basic.Deliver} method
     * containing the received message being rejected.
     * @see com.rabbitmq.client.AMQP.Basic.Reject
     * @param deliveryTag the tag from the received {@link com.rabbitmq.client.AMQP.Basic.GetOk} or {@link com.rabbitmq.client.AMQP.Basic.Deliver}
     * @param requeue true if the rejected message should be requeued rather than discarded/dead-lettered
     * @throws java.io.IOException if an error is encountered
     */
    void basicReject(long deliveryTag, boolean requeue) throws IOException;

channel.basicConsume(queueName, true, consumer)#

  • autoAck:是否自动ack,如果不自动ack,需要使用channel.ackchannel.nackchannel.basicReject 进行消息应答
    /**
     * Start a non-nolocal, non-exclusive consumer, with
     * a server-generated consumerTag.
     * @param queue the name of the queue
     * @param autoAck true if the server should consider messages
     * acknowledged once delivered; false if the server should expect
     * explicit acknowledgements
     * @param callback an interface to the consumer object
     * @return the consumerTag generated by the server
     * @throws java.io.IOException if an error is encountered
     * @see com.rabbitmq.client.AMQP.Basic.Consume
     * @see com.rabbitmq.client.AMQP.Basic.ConsumeOk
     * @see #basicConsume(String, boolean, String, boolean, boolean, Map, Consumer)
     */
    String basicConsume(String queue, boolean autoAck, Consumer callback) throws IOException;

chanel.exchangeBind()#

channel.queueBind(queueName, EXCHANGE_NAME, bindingKey);用于通过绑定bindingKeyqueueExchange,之后便可以进行消息接收

    /**
     * Bind an exchange to an exchange, with no extra arguments.
     * @see com.rabbitmq.client.AMQP.Exchange.Bind
     * @see com.rabbitmq.client.AMQP.Exchange.BindOk
     * @param destination the name of the exchange to which messages flow across the binding
     * @param source the name of the exchange from which messages flow across the binding
     * @param routingKey the routine key to use for the binding
     * @return a binding-confirm method if the binding was successfully created
     * @throws java.io.IOException if an error is encountered
     */
    Exchange.BindOk exchangeBind(String destination, String source, String routingKey) throws IOException;

channel.queueDeclare(queueName, false, false, false, null)#

  • durable:(true、false) true:在服务器重启时,能够存活
  • exclusive :是否为当前连接的专用队列,在连接断开后,会自动删除该队列,生产环境中应该很少用到
  • autodelete:当没有任何消费者使用时,自动删除该队列

this means that the queue will be deleted when there are no more processes consuming messages from it.)

 /**
     * Declare a queue
     * @see com.rabbitmq.client.AMQP.Queue.Declare
     * @see com.rabbitmq.client.AMQP.Queue.DeclareOk
     * @param queue the name of the queue
     * @param durable true if we are declaring a durable queue (the queue will survive a server restart)
     * @param exclusive true if we are declaring an exclusive queue (restricted to this connection)
     * @param autoDelete true if we are declaring an autodelete queue (server will delete it when no longer in use)
     * @param arguments other properties (construction arguments) for the queue
     * @return a declaration-confirm method to indicate the queue was successfully declared
     * @throws java.io.IOException if an error is encountered
     */
    Queue.DeclareOk queueDeclare(String queue, boolean durable, boolean exclusive, boolean autoDelete,
                                 Map<String, Object> arguments) throws IOException;

arguments中可以设置的常用属性

参数名作用示例示例描述
Message TTL设置队列中消息的有效时间{ “x-message-ttl”,1000*8}设置队列中的所有消息的有效期为8s
Auto expire一定的时间内队列没有被使用,则自动删除队列{“x-expires”,1000*60}如果60s没有队列被访问,则删除队列
Max length队列能保存消息的最大条数{“x-max-length”,100 }设置队列最多保存100条消息
Max length bytes队列中ready类型消息的总字节数{“x-max-length-bytes”,1000 }设置队列中ready类型消息总共不能超过1000字节
Overflow behaviour当队列消息满了时,再接收消息时的处理方法。有两种处理方案:默认为"drop-head"模式,表示从队列头部丢弃消息;“reject-publish"表示不接收后续的消息{“x-overflow”,“reject-publish” }设置当队列消息满了时,丢弃传来后续消息
Dead letter exchange用于存储被丢弃的消息的交换机名。Overflow behaviour 的两种处理方案中丢弃的消息都会发送到这个交换机{“x-dead-letter-exchange”,“beiyongExchange” }设置丢弃的消息发送到名字为beiyongExchange的交换机
Dead letter routing key被丢弃的消息发送到Dead letter exchange时的使用的routing Key{“x-dead-letter-routing-key”,“deadKey” }设置丢弃的消息发送到beiyongExchange交换机时的RoutingKey值是"deadKey”
Maximum priority设置队列中消息优先级的最大等级,在publish消息时可以设置单条消息的优先级等级{“x-max-priority”,10 }设置中消息优先级的最大等级为10
Lazy mode设置队列的模式,如果设置为Lazy表示队列中消息尽可能存放在磁盘中,以减少内存占用;不设置时消息都存放在队列中,用以尽可能快的处理消息{“x-queue-mode”,“lazy”}3.6以后版本可用,设置队列中消息尽可能存放在磁盘中,以减少内存占用。在消息拥堵时和消息持久化配置使用可以减少内存占用