This is for bootstrapping and the producer will only use it for getting metadata (topics, partitions and replicas). The socket connections for sending the actual data will be established based on the broker information returned in the metadata. The format is host1:port1,host2:port2, and the list can be a subset of brokers or a VIP pointing to a subset of brokers.
（服务于bootstrapping。producer仅用来获取metadata（topics，partitions，replicas）。发送实际数据的socket连接将基于返回的metadata数据信息而建立。格式是：
host1：port1，host2：port2
这个列表可以是brokers的子列表或者是一个指向brokers的VIP）

This value controls when a produce request is considered completed. Specifically, how many other brokers must have committed the data to their log and acknowledged this to the leader? Typical values are

• 0, which means that the producer never waits for an acknowledgement from the broker (the same behavior as 0.7). This option provides the lowest latency but the weakest durability guarantees (some data will be lost when a server fails).
• 1, which means that the producer gets an acknowledgement after the leader replica has received the data. This option provides better durability as the client waits until the server acknowledges the request as successful (only messages that were written to the now-dead leader but not yet replicated will be lost).
• -1, The producer gets an acknowledgement after all in-sync replicas have received the data. This option provides the greatest level of durability. However, it does not completely eliminate the risk of message loss because the number of in sync replicas may, in rare cases, shrink to 1. If you want to ensure that some minimum number of replicas (typically a majority) receive a write, then you must set the topic-level min.insync.replicas setting. Please read the Replication section of the design documentation for a more in-depth discussion.
  （此配置是表明当一次produce请求被认为完成时的确认值。特别是，多少个其他brokers必须已经提交了数据到他们的log并且向他们的leader确认了这些信息。典型的值包括：
  0： 表示producer从来不等待来自broker的确认信息（和0.7一样的行为）。这个选择提供了最小的时延但同时风险最大（因为当server宕机时，数据将会丢失）。
  1：表示获得leader replica已经接收了数据的确认信息。这个选择时延较小同时确保了server确认接收成功。
  -1：producer会获得所有同步replicas都收到数据的确认。同时时延最大，然而，这种方式并没有完全消除丢失消息的风险，因为同步replicas的数量可能是1.如果你想确保某些replicas接收到数据，那么你应该在topic-level设置中选项min.insync.replicas设置一下。请阅读一下设计文档，可以获得更深入的讨论。）
  

This parameter specifies whether the messages are sent asynchronously in a background thread. Valid values are (1) async for asynchronous send and (2) sync for synchronous send. By setting the producer to async we allow batching together of requests (which is great for throughput) but open the possibility of a failure of the client machine dropping unsent data.
（此选项置顶了消息是否在后台线程中异步发送。正确的值：
（1）  async： 异步发送
（2）  sync： 同步发送
通过将producer设置为异步，我们可以批量处理请求（有利于提高吞吐率）但是这也就造成了客户端机器丢掉未发送数据的可能性）

This parameter allows you to specify the compression codec for all data generated by this producer. Valid values are "none", "gzip" and "snappy".
（此项参数可以设置压缩数据的codec，可选codec为：“none”， “gzip”， “snappy”）

This parameter allows you to set whether compression should be turned on for particular topics. If the compression codec is anything other than NoCompressionCodec, enable compression only for specified topics if any. If the list of compressed topics is empty, then enable the specified compression codec for all topics. If the compression codec is NoCompressionCodec, compression is disabled for all topics
（此项参数可以设置某些特定的topics是否进行压缩。如果压缩codec是NoCompressCodec之外的codec，则对指定的topics数 据应用这些codec。如果压缩topics列表是空，则将特定的压缩codec应用于所有topics。如果压缩的codec是 NoCompressionCodec，压缩对所有topics军不可用。）

This property will cause the producer to automatically retry a failed send request. This property specifies the number of retries when such failures occur. Note that setting a non-zero value here can lead to duplicates in the case of network errors that cause a message to be sent but the acknowledgement to be lost.
（此项参数将使producer自动重试失败的发送请求。此项参数将置顶重试的次数。注意：设定非0值将导致重复某些网络错误：引起一条发送并引起确认丢失）

Before each retry, the producer refreshes the metadata of relevant topics to see if a new leader has been elected. Since leader election takes a bit of time, this property specifies the amount of time that the producer waits before refreshing the metadata.
（在每次重试之前，producer会更新相关topic的metadata，以此进行查看新的leader是否分配好了。因为leader的选择需要一点时间，此选项指定更新metadata之前producer需要等待的时间。）

The producer generally refreshes the topic metadata from brokers when there is a failure (partition missing, leader not available...). It will also poll regularly (default: every 10min so 600000ms). If you set this to a negative value, metadata will only get refreshed on failure. If you set this to zero, the metadata will get refreshed after each message sent (not recommended). Important note: the refresh happen only AFTER the message is sent, so if the producer never sends a message the metadata is never refreshed
（producer一般会在某些失败的情况下（partition missing，leader不可用等）更新topic的metadata。他将会规律的循环。如果你设置为负值，metadata只有在失败的情况下才 更新。如果设置为0，metadata会在每次消息发送后就会更新（不建议这种选择，系统消耗太大）。重要提示： 更新是有在消息发送后才会发生，因此，如果producer从来不发送消息，则metadata从来也不会更新。）

The amount of time to block before dropping messages when running in async mode and the buffer has reached queue.buffering.max.messages. If set to 0 events will be enqueued immediately or dropped if the queue is full (the producer send call will never block). If set to -1 the producer will block indefinitely and never willingly drop a send.