1、查看信息

a、查看topic信息

kafkacat -L -b host:port
kafkacat -L -b host:port -t topic

b、offset by timestamp

kafkacat -Q -b host:port -t topic:partition:timestamp

2、消费者

a、订阅所有消息

kafkacat -C -b host1:port1,host2:port2,host3:port3 -t topic

b、读取制指定个数的消息（可以查看kafka里是否有消息）

kafkacat -C -b host1:port1,host2:port2,host3:port3 -t topic -o -10 -e
kafkacat -C -b host1:port1,host2:port2,host3:port3 -t topic -p 0 -o -10 -e

3、生产者

a、直接发送

kafkacat -b host1:port1,host2:port2,host3:port3 -t topic -P

b、通过管道发送（json字符串）

cat send.txt |  kafkacat -b host1:port1,host2:port2,host3:port3 -t topic  -P

4、转发消息
把接收到的消息转发到生产者

kafkacat -C -b broker1 -t topic1 -e | kafkacat -P -b broker2 -t topic2

5、配置
kafkacat 使用的是librdkafka的配置，使用时可以通过 '-F'指定配置文件。
比如 SASL_PLAINTEXT登录，新建一个配置文件, 如

kafka.conf

security.protocol=SASL_PLAINTEXT
sasl.mechanisms=PLAIN
sasl.username=username
sasl.password=pwd

kafkacat -L -b broker -F kafka.conf

说明：kafkacat --help

General options:
  -C | -P | -L | -Q  Mode: Consume, Produce, Metadata List, Query mode
  -G <group-id>      Mode: High-level KafkaConsumer (Kafka >=0.9 balanced consumer groups)
                     Expects a list of topics to subscribe to
  -t <topic>         Topic to consume from, produce to, or list
  -p <partition>     Partition
  -b <brokers,..>    Bootstrap broker(s) (host[:port])
  -D <delim>         Message delimiter character:
                     a-z.. | \r | \n | \t | \xNN
                     Default: \n
  -E                 Do not exit on non fatal error
  -K <delim>         Key delimiter (same format as -D)
  -c <cnt>           Limit message count
  -m <seconds>       Metadata (et.al.) request timeout.
                     This limits how long kafkacat will block
                     while waiting for initial metadata to be
                     retrieved from the Kafka cluster.
                     It also sets the timeout for the producer's
                     transaction commits, init, aborts, etc.
                     Default: 5 seconds.
  -F <config-file>   Read configuration properties from file,
                     file format is "property=value".
                     The KAFKACAT_CONFIG=path environment can also be used, but -F takes preceedence.
                     The default configuration file is $HOME/.config/kafkacat.conf
  -X list            List available librdkafka configuration properties
  -X prop=val        Set librdkafka configuration property.
                     Properties prefixed with "topic." are
                     applied as topic properties.
  -X schema.registry.prop=val Set libserdes configuration property for the Avro/Schema-Registry client.
  -X dump            Dump configuration and exit.
  -d <dbg1,...>      Enable librdkafka debugging:
                     all,generic,broker,topic,metadata,feature,queue,msg,protocol,cgrp,security,fetch,interceptor,plugin,consumer,admin,eos,mock
  -q                 Be quiet (verbosity set to 0)
  -v                 Increase verbosity
  -V                 Print version
  -h                 Print usage help

Producer options:
  -z snappy|gzip|lz4 Message compression. Default: none
  -p -1              Use random partitioner
  -D <delim>         Delimiter to split input into messages
  -K <delim>         Delimiter to split input key and message
  -k <str>           Use a fixed key for all messages.
                     If combined with -K, per-message keys
                     takes precendence.
  -H <header=value>  Add Message Headers (may be specified multiple times)
  -l                 Send messages from a file separated by
                     delimiter, as with stdin.
                     (only one file allowed)
  -T                 Output sent messages to stdout, acting like tee.
  -c <cnt>           Exit after producing this number of messages
  -Z                 Send empty messages as NULL messages
  file1 file2..      Read messages from files.
                     With -l, only one file permitted.
                     Otherwise, the entire file contents will
                     be sent as one single message.
  -X transactional.id=.. Enable transactions and send all
                     messages in a single transaction which
                     is committed when stdin is closed or the
                     input file(s) are fully read.
                     If kafkacat is terminated through Ctrl-C
                     (et.al) the transaction will be aborted.

Consumer options:
  -o <offset>        Offset to start consuming from:
                     beginning | end | stored |
                     <value>  (absolute offset) |
                     -<value> (relative offset from end)
                     s@<value> (timestamp in ms to start at)
                     e@<value> (timestamp in ms to stop at (not included))
  -e                 Exit successfully when last message received
  -f <fmt..>         Output formatting string, see below.
                     Takes precedence over -D and -K.
  -J                 Output with JSON envelope
  -s key=<serdes>    Deserialize non-NULL keys using <serdes>.
  -s value=<serdes>  Deserialize non-NULL values using <serdes>.
  -s <serdes>        Deserialize non-NULL keys and values using <serdes>.
                     Available deserializers (<serdes>):
                       <pack-str> - A combination of:
                                    <: little-endian,
                                    >: big-endian (recommended),
                                    b: signed 8-bit integer
                                    B: unsigned 8-bit integer
                                    h: signed 16-bit integer
                                    H: unsigned 16-bit integer
                                    i: signed 32-bit integer
                                    I: unsigned 32-bit integer
                                    q: signed 64-bit integer
                                    Q: unsigned 64-bit integer
                                    c: ASCII character
                                    s: remaining data is string
                                    $: match end-of-input (no more bytes remaining or a parse error is raised).
                                       Not including this token skips any
                                       remaining data after the pack-str is
                                       exhausted.
                       avro       - Avro-formatted with schema in Schema-Registry (requires -r)
                     E.g.: -s key=i -s value=avro - key is 32-bit integer, value is Avro.
                       or: -s avro - both key and value are Avro-serialized
  -r <url>           Schema registry URL (requires avro deserializer to be used with -s)
  -D <delim>         Delimiter to separate messages on output
  -K <delim>         Print message keys prefixing the message
                     with specified delimiter.
  -O                 Print message offset using -K delimiter
  -c <cnt>           Exit after consuming this number of messages
  -Z                 Print NULL values and keys as "NULL" instead of empty.
                     For JSON (-J) the nullstr is always null.
  -u                 Unbuffered output

Metadata options (-L):
  -t <topic>         Topic to query (optional)

Query options (-Q):
  -t <t>:<p>:<ts>    Get offset for topic <t>,
                     partition <p>, timestamp <ts>.
                     Timestamp is the number of milliseconds
                     since epoch UTC.
                     Requires broker >= 0.10.0.0 and librdkafka >= 0.9.3.
                     Multiple -t .. are allowed but a partition
                     must only occur once.

Format string tokens:
  %s                 Message payload
  %S                 Message payload length (or -1 for NULL)
  %R                 Message payload length (or -1 for NULL) serialized
                     as a binary big endian 32-bit signed integer
  %k                 Message key
  %K                 Message key length (or -1 for NULL)
  %T                 Message timestamp (milliseconds since epoch UTC)
  %h                 Message headers (n=v CSV)
  %t                 Topic
  %p                 Partition
  %o                 Message offset
  \n \r \t           Newlines, tab
  \xXX \xNNN         Any ASCII character
 Example:
  -f 'Topic %t [%p] at offset %o: key %k: %s\n'

JSON message envelope (on one line) when consuming with -J:
 { "topic": str, "partition": int, "offset": int,
   "tstype": "create|logappend|unknown", "ts": int, // timestamp in milliseconds since epoch
   "broker": int,
   "headers": { "<name>": str, .. }, // optional
   "key": str|json, "payload": str|json,
   "key_error": str, "payload_error": str } //optional
 (note: key_error and payload_error are only included if deserialization failed)

Consumer mode (writes messages to stdout):
  kafkacat -b <broker> -t <topic> -p <partition>
 or:
  kafkacat -C -b ...

High-level KafkaConsumer mode:
  kafkacat -b <broker> -G <group-id> topic1 top2 ^aregex\d+

Producer mode (reads messages from stdin):
  ... | kafkacat -b <broker> -t <topic> -p <partition>
 or:
  kafkacat -P -b ...

Metadata listing:
  kafkacat -L -b <broker> [-t <topic>]

Query offset by timestamp:
  kafkacat -Q -b broker -t <topic>:<partition>:<timestamp>