はじめに
Confluent Platformを使ってみた時のメモ書きです。
今回はコマンドから簡易的にメッセージのやりとりを実施してみます。
関連記事
Confluent Platform メモ - (1)環境構築
Confluent Platform メモ - (2)メッセージ送受信簡易テスト
Confluent Platform メモ - (3)Schema Registry簡易テスト
参考情報
Kafka Commands Primer
Apache Kafkaの用語とコマンド
Apache Kafkaの概要とアーキテクチャ
Kafkaコマンド
/opt/confluent-6.2.0/bin/以下に提供されます。
(これらも実体はシェル・スクリプトで最終的にはJavaプログラムが動くようです)
kafka-topics
Broker上にTopicを作成したりTopicの属性を確認したりするためのコマンドです。
kafka-topics --help
[root@test12 /opt/confluent-6.2.0/bin]# ./kafka-topics --help
This tool helps to create, delete, describe, or change a topic.
Option Description
------ -----------
--alter Alter the number of partitions,
replica assignment, and/or
configuration for the topic.
--at-min-isr-partitions if set when describing topics, only
show partitions whose isr count is
equal to the configured minimum. Not
supported with the --zookeeper
option.
--bootstrap-server <String: server to REQUIRED: The Kafka server to connect
connect to> to. In case of providing this, a
direct Zookeeper connection won't be
required.
--command-config <String: command Property file containing configs to be
config property file> passed to Admin Client. This is used
only with --bootstrap-server option
for describing and altering broker
configs.
--config <String: name=value> A topic configuration override for the
topic being created or altered. The
following is a list of valid
configurations:
cleanup.policy
compression.type
delete.retention.ms
file.delete.delay.ms
flush.messages
flush.ms
follower.replication.throttled.
replicas
index.interval.bytes
leader.replication.throttled.replicas
max.compaction.lag.ms
max.message.bytes
message.downconversion.enable
message.format.version
message.timestamp.difference.max.ms
message.timestamp.type
min.cleanable.dirty.ratio
min.compaction.lag.ms
min.insync.replicas
preallocate
retention.bytes
retention.ms
segment.bytes
segment.index.bytes
segment.jitter.ms
segment.ms
unclean.leader.election.enable
See the Kafka documentation for full
details on the topic configs. It is
supported only in combination with --
create if --bootstrap-server option
is used (the kafka-configs CLI
supports altering topic configs with
a --bootstrap-server option).
--create Create a new topic.
--delete Delete a topic
--delete-config <String: name> A topic configuration override to be
removed for an existing topic (see
the list of configurations under the
--config option). Not supported with
the --bootstrap-server option.
--describe List details for the given topics.
--disable-rack-aware Disable rack aware replica assignment
--exclude-internal exclude internal topics when running
list or describe command. The
internal topics will be listed by
default
--force Suppress console prompts
--help Print usage information.
--if-exists if set when altering or deleting or
describing topics, the action will
only execute if the topic exists.
--if-not-exists if set when creating topics, the
action will only execute if the
topic does not already exist.
--list List all available topics.
--partitions <Integer: # of partitions> The number of partitions for the topic
being created or altered (WARNING:
If partitions are increased for a
topic that has a key, the partition
logic or ordering of the messages
will be affected). If not supplied
for create, defaults to the cluster
default.
--replica-assignment <String: A list of manual partition-to-broker
broker_id_for_part1_replica1 : assignments for the topic being
broker_id_for_part1_replica2 , created or altered.
broker_id_for_part2_replica1 :
broker_id_for_part2_replica2 , ...>
--replication-factor <Integer: The replication factor for each
replication factor> partition in the topic being
created. If not supplied, defaults
to the cluster default.
--topic <String: topic> The topic to create, alter, describe
or delete. It also accepts a regular
expression, except for --create
option. Put topic name in double
quotes and use the '\' prefix to
escape regular expression symbols; e.
g. "test\.topic".
--topics-with-overrides if set when describing topics, only
show topics that have overridden
configs
--unavailable-partitions if set when describing topics, only
show partitions whose leader is not
available
--under-min-isr-partitions if set when describing topics, only
show partitions whose isr count is
less than the configured minimum.
Not supported with the --zookeeper
option.
--under-replicated-partitions if set when describing topics, only
show under replicated partitions
--version Display Kafka version.
--zookeeper <String: hosts> DEPRECATED, The connection string for
the zookeeper connection in the form
host:port. Multiple hosts can be
given to allow fail-over.
kafka-console-producer
Producerとしての役割を担うコマンドです。シェルから対話的にメッセージを送信することができます。
kafka-console-producer --help
[root@test12 /opt/confluent-6.2.0/bin]# ./kafka-console-producer --help
This tool helps to read data from standard input and publish it to Kafka.
Option Description
------ -----------
--batch-size <Integer: size> Number of messages to send in a single
batch if they are not being sent
synchronously. (default: 200)
--bootstrap-server <String: server to REQUIRED unless --broker-list
connect to> (deprecated) is specified. The server
(s) to connect to. The broker list
string in the form HOST1:PORT1,HOST2:
PORT2.
--broker-list <String: broker-list> DEPRECATED, use --bootstrap-server
instead; ignored if --bootstrap-
server is specified. The broker
list string in the form HOST1:PORT1,
HOST2:PORT2.
--compression-codec [String: The compression codec: either 'none',
compression-codec] 'gzip', 'snappy', 'lz4', or 'zstd'.
If specified without value, then it
defaults to 'gzip'
--help Print usage information.
--line-reader <String: reader_class> The class name of the class to use for
reading lines from standard in. By
default each line is read as a
separate message. (default: kafka.
tools.
ConsoleProducer$LineMessageReader)
--max-block-ms <Long: max block on The max time that the producer will
send> block for during a send request
(default: 60000)
--max-memory-bytes <Long: total memory The total memory used by the producer
in bytes> to buffer records waiting to be sent
to the server. (default: 33554432)
--max-partition-memory-bytes <Long: The buffer size allocated for a
memory in bytes per partition> partition. When records are received
which are smaller than this size the
producer will attempt to
optimistically group them together
until this size is reached.
(default: 16384)
--message-send-max-retries <Integer> Brokers can fail receiving the message
for multiple reasons, and being
unavailable transiently is just one
of them. This property specifies the
number of retries before the
producer give up and drop this
message. (default: 3)
--metadata-expiry-ms <Long: metadata The period of time in milliseconds
expiration interval> after which we force a refresh of
metadata even if we haven't seen any
leadership changes. (default: 300000)
--producer-property <String: A mechanism to pass user-defined
producer_prop> properties in the form key=value to
the producer.
--producer.config <String: config file> Producer config properties file. Note
that [producer-property] takes
precedence over this config.
--property <String: prop> A mechanism to pass user-defined
properties in the form key=value to
the message reader. This allows
custom configuration for a user-
defined message reader. Default
properties include:
parse.key=true|false
key.separator=<key.separator>
ignore.error=true|false
--request-required-acks <String: The required acks of the producer
request required acks> requests (default: 1)
--request-timeout-ms <Integer: request The ack timeout of the producer
timeout ms> requests. Value must be non-negative
and non-zero (default: 1500)
--retry-backoff-ms <Integer> Before each retry, the producer
refreshes the metadata of relevant
topics. Since leader election takes
a bit of time, this property
specifies the amount of time that
the producer waits before refreshing
the metadata. (default: 100)
--socket-buffer-size <Integer: size> The size of the tcp RECV size.
(default: 102400)
--sync If set message send requests to the
brokers are synchronously, one at a
time as they arrive.
--timeout <Integer: timeout_ms> If set and the producer is running in
asynchronous mode, this gives the
maximum amount of time a message
will queue awaiting sufficient batch
size. The value is given in ms.
(default: 1000)
--topic <String: topic> REQUIRED: The topic id to produce
messages to.
--version Display Kafka version.
kafka-console-consumer
Consumerとしての役割を担うコマンドです。シェルからメッセージを受信することができます。
kafka-console-consumer --help
[root@test12 /opt/confluent-6.2.0/bin]# ./kafka-console-consumer --help
This tool helps to read data from Kafka topics and outputs it to standard output.
Option Description
------ -----------
--bootstrap-server <String: server to REQUIRED: The server(s) to connect to.
connect to>
--consumer-property <String: A mechanism to pass user-defined
consumer_prop> properties in the form key=value to
the consumer.
--consumer.config <String: config file> Consumer config properties file. Note
that [consumer-property] takes
precedence over this config.
--enable-systest-events Log lifecycle events of the consumer
in addition to logging consumed
messages. (This is specific for
system tests.)
--formatter <String: class> The name of a class to use for
formatting kafka messages for
display. (default: kafka.tools.
DefaultMessageFormatter)
--from-beginning If the consumer does not already have
an established offset to consume
from, start with the earliest
message present in the log rather
than the latest message.
--group <String: consumer group id> The consumer group id of the consumer.
--help Print usage information.
--isolation-level <String> Set to read_committed in order to
filter out transactional messages
which are not committed. Set to
read_uncommitted to read all
messages. (default: read_uncommitted)
--key-deserializer <String:
deserializer for key>
--max-messages <Integer: num_messages> The maximum number of messages to
consume before exiting. If not set,
consumption is continual.
--offset <String: consume offset> The offset id to consume from (a non-
negative number), or 'earliest'
which means from beginning, or
'latest' which means from end
(default: latest)
--partition <Integer: partition> The partition to consume from.
Consumption starts from the end of
the partition unless '--offset' is
specified.
--property <String: prop> The properties to initialize the
message formatter. Default
properties include:
print.timestamp=true|false
print.key=true|false
print.offset=true|false
print.partition=true|false
print.headers=true|false
print.value=true|false
key.separator=<key.separator>
line.separator=<line.separator>
headers.separator=<line.separator>
null.literal=<null.literal>
key.deserializer=<key.deserializer>
value.deserializer=<value.
deserializer>
header.deserializer=<header.
deserializer>
Users can also pass in customized
properties for their formatter; more
specifically, users can pass in
properties keyed with 'key.
deserializer.', 'value.
deserializer.' and 'headers.
deserializer.' prefixes to configure
their deserializers.
--skip-message-on-error If there is an error when processing a
message, skip it instead of halt.
--timeout-ms <Integer: timeout_ms> If specified, exit if no message is
available for consumption for the
specified interval.
--topic <String: topic> The topic id to consume on.
--value-deserializer <String:
deserializer for values>
--version Display Kafka version.
--whitelist <String: whitelist> Regular expression specifying
whitelist of topics to include for
consumption.
kafka-delete-records
KafkaのメッセージはMQとは違ってConsumerでメッセージ受信してもTopicに残ったままになっているようです。結構衝撃の事実でした。
Consumerでメッセージを受信すると"Consumed"とマークされるだけでそのタイミングでは消されません。そのため複数のConsumerから何度も同じメッセージを読むことができるようです。
じゃぁいつ消えるのよ！というのが気になって調べると、以下の様な記述がありました。
Kafka stores records for topics on disk and retains that data even once consumers have read it. However, records aren’t stored in one big file but are broken up into segments by partition where the offset order is continuous across segments for the same topic partition. Because servers do not have infinite amounts of storage, Kafka provides settings to control how much data is retained, based on time and size:
- The time configuration controlling data retention is log.retention.hours, which defaults to 168 hours (one week)
- The size configuration log.retention.bytes controls how large segments can grow before they are eligible for deletion
時間とサイズで消すタイミングがコントロールされているようですが、なんとデフォルトでは7日間保持されるらしい。
上の記事のリンクにはメッセージの手動での削除方法が記載されています。どのメッセージを消すかをJSONファイルとして作成してそれを引数にkafka-delete-recordsコマンドを実行するらしいです。なんと面倒な！全メッセージ消すのであれば、Topic自体を削除/再作成するのが早いかもしれません。
kafka-delete-records --help
[root@test12 /opt/confluent-6.2.0/bin]# ./kafka-delete-records --help
This tool helps to delete records of the given partitions down to the specified offset.
Option Description
------ -----------
--bootstrap-server <String: server(s) REQUIRED: The server to connect to.
to use for bootstrapping>
--command-config <String: command A property file containing configs to
config property file path> be passed to Admin Client.
--help Print usage information.
--offset-json-file <String: Offset REQUIRED: The JSON file with offset
json file path> per partition. The format to use is:
{"partitions":
[{"topic": "foo", "partition": 1,
"offset": 1}],
"version":1
}
--version Display Kafka version.
offset-json-file例
offsets.json
{
"partitions": [
{"topic": "cool-topic", "partition": 0, "offset": -1}
],
"version":1
}
offsetに-1を指定すると全メッセージが削除されるようです。
操作例
以下の記述を参考にいくつかコマンドを試してみます。
Kafka Commands Primer
イメージ:
Topic作成
cool-topicという名前のTopicを作成してみます。
[root@test12 /opt/confluent-6.2.0/bin]# ./kafka-topics --create --topic cool-topic --bootstrap-server localhost:9092
Created topic cool-topic.
[root@test12 /opt/confluent-6.2.0/bin]# ./kafka-topics --list --bootstrap-server localhost:9092
__consumer_offsets
_schemas
cool-topic
cool-topicの詳細情報を確認します。
[root@test12 /opt/confluent-6.2.0/bin]# ./kafka-topics --describe --topic cool-topic --bootstrap-server localhost:9092
Topic: cool-topic TopicId: Z8vfn8oqQW6LwUl9N_myAA PartitionCount: 1 ReplicationFactor: 1 Configs: segment.bytes=1073741824
Topic: cool-topic Partition: 0 Leader: 0 Replicas: 0 Isr: 0
Producer / メッセージ送信
kafka-console-producerコマンドを実行するとプロンプト(>)が表示されるので、そこに送信したいメッセージを入力していきます。エンターを押すたびにその一行分の文字列が1メッセージとして送信されます。
[root@test12 /opt/confluent-6.2.0/bin]# ./kafka-console-producer --topic cool-topic --bootstrap-server localhost:9092
>hello
>first
>second
>third
>end
>^C
最後にCtrl+Cで抜けます。
これで5つのメッセージが送信されました。
Consumer / メッセージ受信
cool-topicのメッセージを受信します。
[root@test12 /opt/confluent-6.2.0/bin]# ./kafka-console-consumer --bootstrap-server localhost:9092 --from-beginning --topic cool-topic
hello
first
second
third
end
^CProcessed a total of 5 messages
最後にCtrl+Cで抜けます。
Topic削除
cool-topicを削除します。
[root@test12 /opt/confluent-6.2.0/bin]# ./kafka-topics --delete --topic cool-topic --bootstrap-server localhost:9092
[root@test12 /opt/confluent-6.2.0/bin]# ./kafka-topics --list --bootstrap-server localhost:9092
__consumer_offsets
_schemas