3.2 Consumer 配置
The essential consumer configurations are the following:
基本消费配置如下:
- group.id
- zookeeper.connect
More details about consumer configuration can be found in the scala classkafka.consumer.ConsumerConfig.
更多细节可以查看 scala类： kafka.consumer.ConsumerConfig
| Property | Default | Description |
|---|---|---|
| group.id |
|
A string that uniquely identifies the group of consumer
processes to which this consumer belongs. By setting the same group id
multiple processes indicate that they are all part of the same consumer
group. （用来唯一标识consumer进程所在组的字符串，如果设置同样的group id，表示这些processes都是属于同一个consumer group） |
| zookeeper.connect |
|
Specifies the ZooKeeper connection string in the formhostname:portwhere host and port are the host and port of a ZooKeeper server. To
allow connecting through other ZooKeeper nodes when that ZooKeeper
machine is down you can also specify multiple hosts in the formhostname1:port1,hostname2:port2,hostname3:port3.
The server may also have a ZooKeeper chroot path as part of it's
ZooKeeper connection string which puts its data under some path in the
global ZooKeeper namespace. If so the consumer should use the same
chroot path in its connection string. For example to give a chroot path
of/chroot/pathyou would give the connection string ashostname1:port1,hostname2:port2,hostname3:port3/chroot/path. |
| consumer.id | null |
Generated automatically if not set. |
| socket.timeout.ms | 30 * 1000 |
The socket timeout for network requests. The actual timeout set will be max.fetch.wait + socket.timeout.ms. （网络请求的超时限制。真实的超时限制是 max.fetch.wait+socket.timeout.ms） |
| socket.receive.buffer.bytes | 64 * 1024 |
The socket receive buffer for network requests （socket用于接收网络请求的缓存大小） |
| fetch.message.max.bytes | 1024 * 1024 |
The number of byes of messages to attempt to fetch for each
topic-partition in each fetch request. These bytes will be read into
memory for each partition, so this helps control the memory used by the
consumer. The fetch request size must be at least as large as the
maximum message size the server allows or else it is possible for the
producer to send messages larger than the consumer can fetch. （每次fetch请求中，针对每次fetch消息的最大字节数。这些字节将会督导用于每个partition的内存中，因此，此设置将会控制 consumer所使用的memory大小。这个fetch请求尺寸必须至少和server允许的最大消息尺寸相等，否则，producer可能发送的消 息尺寸大于consumer所能消耗的尺寸。） |
| num.consumer.fetchers | 1 |
The number fetcher threads used to fetch data. （用于fetch数据的fetcher线程数） |
| auto.commit.enable | true |
If true, periodically commit to ZooKeeper the offset of
messages already fetched by the consumer. This committed offset will be
used when the process fails as the position from which the new consumer
will begin. （如果为真，consumer所fetch的消息的offset将会自动的同步到zookeeper。这项提交的offset将在进程挂掉时，由新的consumer使用） |
| auto.commit.interval.ms | 60 * 1000 |
The frequency in ms that the consumer offsets are committed to zookeeper. （consumer向zookeeper提交offset的频率，单位是ms） |
| queued.max.message.chunks | 2 |
Max number of message chunks buffered for consumption. Each chunk can be up to fetch.message.max.bytes. （用于缓存消息的最大数目，以供consumption。每个chunk必须和fetch.message.max.bytes相同） |
| rebalance.max.retries | 4 |
When a new consumer joins a consumer group the set of
consumers attempt to "rebalance" the load to assign partitions to each
consumer. If the set of consumers changes while this assignment is
taking place the rebalance will fail and retry. This setting controls
the maximum number of attempts before giving up. （当新的consumer加入到consumer group时，consumers集合试图重新平衡分配到每个consumer的partitions数目。如果consumers集合改变了，当分配正在执行时，这个重新平衡会失败并重入，放弃尝试的最大次数） |
| fetch.min.bytes | 1 |
The minimum amount of data the server should return for a
fetch request. If insufficient data is available the request will wait
for that much data to accumulate before answering the request. （每次fetch请求时，server应该返回的最小字节数。如果没有足够的数据返回，请求会等待，直到足够的数据才会返回。） |
| fetch.wait.max.ms | 100 |
The maximum amount of time the server will block before
answering the fetch request if there isn't sufficient data to
immediately satisfy fetch.min.bytes （如果没有足够的数据能够满足fetch.min.bytes，则此项配置是指在应答fetch请求之前，server会阻塞的最大时间。） |
| rebalance.backoff.ms | 2000 |
Backoff time between retries during rebalance. （在重试reblance之前backoff时间） |
| refresh.leader.backoff.ms | 200 |
Backoff time to wait before trying to determine the leader of a partition that has just lost its leader. （在试图确定某个partition的leader是否失去他的leader地位之前，需要等待的backoff时间） |
| auto.offset.reset | largest |
What to do when there is no initial offset in ZooKeeper or if an offset is out of range: |
| consumer.timeout.ms | -1 |
Throw a timeout exception to the consumer if no message is available for consumption after the specified interval （如果没有消息可用，即使等待特定的时间之后也没有，则抛出超时异常） |
| exclude.internal.topics | true |
Whether messages from internal topics (such as offsets) should be exposed to the consumer. （是否将内部topics的消息暴露给consumer） |
| partition.assignment.strategy | range |
Select a strategy for assigning partitions to consumer streams. Possible values: range, roundrobin. （选择向consumer 流分配partitions的策略，可选值：range，roundrobin） |
| client.id | group id value |
The client id is a user-specified string sent in each request
to help trace calls. It should logically identify the application making
the request. （是用户特定的字符串，用来在每次请求中帮助跟踪调用。它应该可以逻辑上确认产生这个请求的应用） |
| zookeeper.session.timeout.ms | 6000 |
ZooKeeper session timeout. If the consumer fails to heartbeat
to ZooKeeper for this period of time it is considered dead and a
rebalance will occur. （zookeeper 会话的超时限制。如果consumer在这段时间内没有向zookeeper发送心跳信息，则它会被认为挂掉了，并且reblance将会产生） |
| zookeeper.connection.timeout.ms | 6000 |
The max time that the client waits while establishing a connection to zookeeper. （客户端在建立通zookeeper连接中的最大等待时间） |
| zookeeper.sync.time.ms | 2000 |
How far a ZK follower can be behind a ZK leader （ZK follower可以落后ZK leader的最大时间） |
| offsets.storage | zookeeper |
Select where offsets should be stored (zookeeper or kafka). （用于存放offsets的地点： zookeeper或者kafka） |
| offsets.channel.backoff.ms | 1000 |
The backoff period when reconnecting the offsets channel or retrying failed offset fetch/commit requests. （重新连接offsets channel或者是重试失败的offset的fetch/commit请求的backoff时间） |
| offsets.channel.socket.timeout.ms | 10000 |
Socket timeout when reading responses for offset fetch/commit
requests. This timeout is also used for ConsumerMetadata requests that
are used to query for the offset manager. （当读取offset的fetch/commit请求回应的socket 超时限制。此超时限制是被consumerMetadata请求用来请求offset管理） |
| offsets.commit.max.retries | 5 |
Retry the offset commit up to this many times on failure. This
retry count only applies to offset commits during shut-down. It does
not apply to commits originating from the auto-commit thread. It also
does not apply to attempts to query for the offset coordinator before
committing offsets. i.e., if a consumer metadata request fails for any
reason, it will be retried and that retry does not count toward this
limit. （重试offset commit的次数。这个重试只应用于offset commits在shut-down之间。） |
| dual.commit.enabled | true |
If you are using "kafka" as offsets.storage, you can dual
commit offsets to ZooKeeper (in addition to Kafka). This is required
during migration from zookeeper-based offset storage to kafka-based
offset storage. With respect to any given consumer group, it is safe to
turn this off after all instances within that group have been migrated
to the new version that commits offsets to the broker (instead of
directly to ZooKeeper). （如果使用“kafka”作为offsets.storage，你可以二次提交offset到zookeeper(还有一次是提交到kafka）。在 zookeeper-based的offset storage到kafka-based的offset storage迁移时，这是必须的。对任意给定的consumer group来说，比较安全的建议是当完成迁移之后就关闭这个选项） |
| partition.assignment.strategy | range |
Select between the "range" or "roundrobin" strategy for assigning partitions to consumer streams. The round-robin partition assignor lays out all the available partitions and all the available consumer threads. It then proceeds to do a round-robin assignment from partition to consumer thread. If the subscriptions of all consumer instances are identical, then the partitions will be uniformly distributed. (i.e., the partition ownership counts will be within a delta of exactly one across all consumer threads.) Round-robin assignment is permitted only if: (a) Every topic has the same number of streams within a consumer instance (b) The set of subscribed topics is identical for every consumer instance within the group.
Range partitioning works on a per-topic basis. For each
topic, we lay out the available partitions in numeric order and the
consumer threads in lexicographic order. We then divide the number of
partitions by the total number of consumer streams (threads) to
determine the number of partitions to assign to each consumer. If it
does not evenly divide, then the first few consumers will have one extra
partition. |
More details about consumer configuration can be found in the scala classkafka.consumer.ConsumerConfig.
更多细节可以查看 scala类： kafka.consumer.ConsumerConfig
