fluent-plugin-kafka, a plugin for Fluentd
A fluentd plugin to both consume and produce data for Apache Kafka.
Add this line to your application's Gemfile:
gem 'fluent-plugin-kafka'
And then execute:
$ bundle
Or install it yourself as:
$ gem install fluent-plugin-kafka --no-document
If you want to use zookeeper related parameters, you also need to install zookeeper gem. zookeeper gem includes native extension, so development tools are needed, e.g. ruby-devel, gcc, make and etc.
- Ruby 2.1 or later
- Input plugins work with kafka v0.9 or later
- Output plugins work with kafka v0.8 or later
- ssl_ca_cert
- ssl_client_cert
- ssl_client_cert_key
- ssl_client_cert_key_password
- ssl_ca_certs_from_system
Set path to SSL related files. See Encryption and Authentication using SSL for more detail.
- principal
- keytab
Set principal and path to keytab for SASL/GSSAPI authentication. See Authentication using SASL for more details.
- username
- password
- scram_mechanism
- sasl_over_ssl
Set username, password, scram_mechanism and sasl_over_ssl for SASL/Plain or Scram authentication. See Authentication using SASL for more details.
Consume events by single consumer.
<source>
@type kafka
brokers <broker1_host>:<broker1_port>,<broker2_host>:<broker2_port>,..
topics <listening topics(separate with comma',')>
format <input text type (text|json|ltsv|msgpack)> :default => json
message_key <key (Optional, for text format only, default is message)>
add_prefix <tag prefix (Optional)>
add_suffix <tag suffix (Optional)>
# Optionally, you can manage topic offset by using zookeeper
offset_zookeeper <zookeer node list (<zookeeper1_host>:<zookeeper1_port>,<zookeeper2_host>:<zookeeper2_port>,..)>
offset_zk_root_node <offset path in zookeeper> default => '/fluent-plugin-kafka'
# ruby-kafka consumer options
max_bytes (integer) :default => nil (Use default of ruby-kafka)
max_wait_time (integer) :default => nil (Use default of ruby-kafka)
min_bytes (integer) :default => nil (Use default of ruby-kafka)
</source>
Supports a start of processing from the assigned offset for specific topics.
<source>
@type kafka
brokers <broker1_host>:<broker1_port>,<broker2_host>:<broker2_port>,..
format <input text type (text|json|ltsv|msgpack)>
<topic>
topic <listening topic>
partition <listening partition: default=0>
offset <listening start offset: default=-1>
</topic>
<topic>
topic <listening topic>
partition <listening partition: default=0>
offset <listening start offset: default=-1>
</topic>
</source>
See also ruby-kafka README for more detailed documentation about ruby-kafka.
Consuming topic name is used for event tag. So when the target topic name is app_event, the tag is app_event. If you want to modify tag, use add_prefix or add_suffix parameters. With add_prefix kafka, the tag is kafka.app_event.
Consume events by kafka consumer group features..
<source>
@type kafka_group
brokers <broker1_host>:<broker1_port>,<broker2_host>:<broker2_port>,..
consumer_group <consumer group name, must set>
topics <listening topics(separate with comma',')>
format <input text type (text|json|ltsv|msgpack)> :default => json
message_key <key (Optional, for text format only, default is message)>
kafka_message_key <key (Optional, If specified, set kafka's message key to this key)>
add_headers <If true, add kafka's message headers to record>
add_prefix <tag prefix (Optional)>
add_suffix <tag suffix (Optional)>
retry_emit_limit <Wait retry_emit_limit x 1s when BuffereQueueLimitError happens. The default is nil and it means waiting until BufferQueueLimitError is resolved>
use_record_time (Deprecated. Use 'time_source record' instead.) <If true, replace event time with contents of 'time' field of fetched record>
time_source <source for message timestamp (now|kafka|record)> :default => now
time_format <string (Optional when use_record_time is used)>
# ruby-kafka consumer options
max_bytes (integer) :default => 1048576
max_wait_time (integer) :default => nil (Use default of ruby-kafka)
min_bytes (integer) :default => nil (Use default of ruby-kafka)
offset_commit_interval (integer) :default => nil (Use default of ruby-kafka)
offset_commit_threshold (integer) :default => nil (Use default of ruby-kafka)
fetcher_max_queue_size (integer) :default => nil (Use default of ruby-kafka)
refresh_topic_interval (integer) :default => nil (Use default of ruby-kafka)
start_from_beginning (bool) :default => true
</source>
See also ruby-kafka README for more detailed documentation about ruby-kafka options.
topics supports regex pattern since v0.13.1. If you want to use regex pattern, use /pattern/ like /foo.*/.
Consuming topic name is used for event tag. So when the target topic name is app_event, the tag is app_event. If you want to modify tag, use add_prefix or add_suffix parameter. With add_prefix kafka, the tag is kafka.app_event.
With the introduction of the rdkafka-ruby based input plugin we hope to support Kafka brokers above version 2.1 where we saw compatibility issues when using the ruby-kafka based @kafka_group input type. The rdkafka-ruby lib wraps the highly performant and production ready librdkafka C lib.
<source>
@type rdkafka_group
topics <listening topics(separate with comma',')>
format <input text type (text|json|ltsv|msgpack)> :default => json
message_key <key (Optional, for text format only, default is message)>
kafka_message_key <key (Optional, If specified, set kafka's message key to this key)>
add_headers <If true, add kafka's message headers to record>
add_prefix <tag prefix (Optional)>
add_suffix <tag suffix (Optional)>
retry_emit_limit <Wait retry_emit_limit x 1s when BuffereQueueLimitError happens. The default is nil and it means waiting until BufferQueueLimitError is resolved>
use_record_time (Deprecated. Use 'time_source record' instead.) <If true, replace event time with contents of 'time' field of fetched record>
time_source <source for message timestamp (now|kafka|record)> :default => now
time_format <string (Optional when use_record_time is used)>
# kafka consumer options
max_wait_time_ms 500
max_batch_size 10000
kafka_configs {
"bootstrap.servers": "brokers <broker1_host>:<broker1_port>,<broker2_host>:<broker2_port>",
"group.id": "<consumer group name>"
}
</source>
See also rdkafka-ruby and librdkafka for more detailed documentation about Kafka consumer options.
Consuming topic name is used for event tag. So when the target topic name is app_event, the tag is app_event. If you want to modify tag, use add_prefix or add_suffix parameter. With add_prefix kafka, the tag is kafka.app_event.
This kafka2 plugin is for fluentd v1 or later. This plugin uses ruby-kafka producer for writing data.
If ruby-kafka doesn't fit your kafka environment, check rdkafka2 plugin instead. This will be out_kafka plugin in the future.
<match app.**>
@type kafka2
brokers <broker1_host>:<broker1_port>,<broker2_host>:<broker2_port>,.. # Set brokers directly
# Kafka topic, placerholders are supported. Chunk keys are required in the Buffer section inorder for placeholders
# to work.
topic (string) :default => nil
topic_key (string) :default => 'topic'
partition_key (string) :default => 'partition'
partition_key_key (string) :default => 'partition_key'
message_key_key (string) :default => 'message_key'
default_topic (string) :default => nil
default_partition_key (string) :default => nil
record_key (string) :default => nil
default_message_key (string) :default => nil
exclude_topic_key (bool) :default => false
exclude_partition_key (bool) :default => false
exclude_partition (bool) :default => false
exclude_message_key (bool) :default => false
get_kafka_client_log (bool) :default => false
headers (hash) :default => {}
headers_from_record (hash) :default => {}
use_event_time (bool) :default => false
use_default_for_unknown_topic (bool) :default => false
discard_kafka_delivery_failed (bool) :default => false (No discard)
partitioner_hash_function (enum) (crc32|murmur2) :default => 'crc32'
share_producer (bool) :default => false
# If you intend to rely on AWS IAM auth to MSK with long lived credentials
# https://docs.aws.amazon.com/msk/latest/developerguide/iam-access-control.html
#
# For AWS STS support, see status in
# - https://github.com/zendesk/ruby-kafka/issues/944
# - https://github.com/zendesk/ruby-kafka/pull/951
sasl_aws_msk_iam_access_key_id (string) :default => nil
sasl_aws_msk_iam_secret_key_id (string) :default => nil
sasl_aws_msk_iam_aws_region (string) :default => nil
<format>
@type (json|ltsv|msgpack|attr:<record name>|<formatter name>) :default => json
</format>
# Optional. See https://docs.fluentd.org/v/1.0/configuration/inject-section
<inject>
tag_key tag
time_key time
</inject>
# See fluentd document for buffer related parameters: https://docs.fluentd.org/v/1.0/configuration/buffer-section
# Buffer chunk key should be same with topic_key. If value is not found in the record, default_topic is used.
<buffer topic>
flush_interval 10s
</buffer>
# ruby-kafka producer options
idempotent (bool) :default => false
sasl_over_ssl (bool) :default => true
max_send_retries (integer) :default => 1
required_acks (integer) :default => -1
ack_timeout (integer) :default => nil (Use default of ruby-kafka)
compression_codec (string) :default => nil (No compression. Depends on ruby-kafka: https://github.com/zendesk/ruby-kafka#compression)
</match>
The <formatter name> in <format> uses fluentd's formatter plugins. See formatter article.
Note: Java based Kafka client uses murmur2 as partitioner function by default. If you want to use same partitioning behavior with fluent-plugin-kafka, change it to murmur2 instead of crc32. Note that for using murmur2 hash partitioner function, you must install digest-murmurhash gem.
ruby-kafka sometimes returns Kafka::DeliveryFailed error without good information.
In this case, get_kafka_client_log is useful for identifying the error cause.
ruby-kafka's log is routed to fluentd log so you can see ruby-kafka's log in fluentd logs.
Supports following ruby-kafka's producer options.
- max_send_retries - default: 2 - Number of times to retry sending of messages to a leader.
- required_acks - default: -1 - The number of acks required per request. If you need flush performance, set lower value, e.g. 1, 2.
- ack_timeout - default: nil - How long the producer waits for acks. The unit is seconds.
- compression_codec - default: nil - The codec the producer uses to compress messages.
- max_send_limit_bytes - default: nil - Max byte size to send message to avoid MessageSizeTooLarge. For example, if you set 1000000(message.max.bytes in kafka), Message more than 1000000 byes will be dropped.
- discard_kafka_delivery_failed - default: false - discard the record where Kafka::DeliveryFailed occurred
If you want to know about detail of monitoring, see also https://github.com/zendesk/ruby-kafka#monitoring
See also Kafka::Client for more detailed documentation about ruby-kafka.
This plugin supports compression codec "snappy" also. Install snappy module before you use snappy compression.
$ gem install snappy --no-document
snappy gem uses native extension, so you need to install several packages before. On Ubuntu, need development packages and snappy library.
$ sudo apt-get install build-essential autoconf automake libtool libsnappy-dev
On CentOS 7 installation is also necessary.
$ sudo yum install gcc autoconf automake libtool snappy-devel
This plugin supports compression codec "lz4" also. Install extlz4 module before you use lz4 compression.
$ gem install extlz4 --no-document
This plugin supports compression codec "zstd" also. Install zstd-ruby module before you use zstd compression.
$ gem install zstd-ruby --no-document
Messages will be assigned a partition at random as default by ruby-kafka, but messages with the same partition key will always be assigned to the same partition by setting default_partition_key in config file.
If key name partition_key_key exists in a message, this plugin set the value of partition_key_key as key.
| default_partition_key | partition_key_key | behavior |
|---|---|---|
| Not set | Not exists | All messages are assigned a partition at random |
| Set | Not exists | All messages are assigned to the specific partition |
| Not set | Exists | Messages which have partition_key_key record are assigned to the specific partition, others are assigned a partition at random |
| Set | Exists | Messages which have partition_key_key record are assigned to the specific partition with partition_key_key, others are assigned to the specific partition with default_parition_key |
If key name message_key_key exists in a message, this plugin publishes the value of message_key_key to kafka and can be read by consumers. Same message key will be assigned to all messages by setting default_message_key in config file. If message_key_key exists and if partition_key_key is not set explicitly, messsage_key_key will be used for partitioning.
It is possible to set headers on Kafka messages. This only works for kafka2 and rdkafka2 output plugin.
The format is like key1:value1,key2:value2. For example:
<match app.**>
@type kafka2
[...]
headers some_header_name:some_header_value
<match>
You may set header values based on a value of a fluentd record field. For example, imagine a fluentd record like:
{"source": { "ip": "127.0.0.1" }, "payload": "hello world" }
And the following fluentd config:
<match app.**>
@type kafka2
[...]
headers_from_record source_ip:$.source.ip
<match>
The Kafka message will have a header of source_ip=12.7.0.0.1.
The configuration format is jsonpath. It is descibed in https://docs.fluentd.org/plugin-helper-overview/api-plugin-helper-record_accessor
Fields can be excluded from output data. Only works for kafka2 and rdkafka2 output plugin.
Fields must be specified using an array of dot notation $., for example:
<match app.**>
@type kafka2
[...]
exclude_fields $.source.ip,$.HTTP_FOO
<match>
This config can be used to remove fields used on another configs.
For example, $.source.ip can be extracted with config headers_from_record and excluded from message payload.
Using this config to remove unused fields is discouraged. A filter plugin can be used for this purpose.
If record_key is provided, the plugin sends only a sub field given by that key.
The configuration format is jsonpath.
e.g. When the following configuration and the incoming record are given:
configuration:
<match **>
@type kafka2
[...]
record_key '$.data'
</match>
record:
{
"specversion" : "1.0",
"type" : "com.example.someevent",
"id" : "C234-1234-1234",
"time" : "2018-04-05T17:31:00Z",
"datacontenttype" : "application/json",
"data" : {
"appinfoA" : "abc",
"appinfoB" : 123,
"appinfoC" : true
},
...
}
only the data field will be serialized by the formatter and sent to Kafka.
The toplevel data key will be removed.
This plugin uses ruby-kafka producer for writing data. This plugin is for v0.12. If you use v1, see kafka2.
Support of fluentd v0.12 has ended. kafka_buffered will be an alias of kafka2 and will be removed in the future.
<match app.**>
@type kafka_buffered
# Brokers: you can choose either brokers or zookeeper. If you are not familiar with zookeeper, use brokers parameters.
brokers <broker1_host>:<broker1_port>,<broker2_host>:<broker2_port>,.. # Set brokers directly
zookeeper <zookeeper_host>:<zookeeper_port> # Set brokers via Zookeeper
zookeeper_path <broker path in zookeeper> :default => /brokers/ids # Set path in zookeeper for kafka
topic_key (string) :default => 'topic'
partition_key (string) :default => 'partition'
partition_key_key (string) :default => 'partition_key'
message_key_key (string) :default => 'message_key'
default_topic (string) :default => nil
default_partition_key (string) :default => nil
default_message_key (string) :default => nil
exclude_topic_key (bool) :default => false
exclude_partition_key (bool) :default => false
exclude_partition (bool) :default => false
exclude_message_key (bool) :default => false
output_data_type (json|ltsv|msgpack|attr:<record name>|<formatter name>) :default => json
output_include_tag (bool) :default => false
output_include_time (bool) :default => false
exclude_topic_key (bool) :default => false
exclude_partition_key (bool) :default => false
get_kafka_client_log (bool) :default => false
use_event_time (bool) :default => false
partitioner_hash_function (enum) (crc32|murmur2) :default => 'crc32'
# See fluentd document for buffer related parameters: https://docs.fluentd.org/v/0.12/buffer
# ruby-kafka producer options
idempotent (bool) :default => false
sasl_over_ssl (bool) :default => true
max_send_retries (integer) :default => 1
required_acks (integer) :default => -1
ack_timeout (integer) :default => nil (Use default of ruby-kafka)
compression_codec (string) :default => nil (No compression. Depends on ruby-kafka: https://github.com/zendesk/ruby-kafka#compression)
kafka_agg_max_bytes (integer) :default => 4096
kafka_agg_max_messages (integer) :default => nil (No limit)
max_send_limit_bytes (integer) :default => nil (No drop)
discard_kafka_delivery_failed (bool) :default => false (No discard)
monitoring_list (array) :default => []
</match>
kafka_buffered supports the following ruby-kafka parameters:
- max_send_retries - default: 2 - Number of times to retry sending of messages to a leader.
- required_acks - default: -1 - The number of acks required per request. If you need flush performance, set lower value, e.g. 1, 2.
- ack_timeout - default: nil - How long the producer waits for acks. The unit is seconds.
- compression_codec - default: nil - The codec the producer uses to compress messages.
- max_send_limit_bytes - default: nil - Max byte size to send message to avoid MessageSizeTooLarge. For example, if you set 1000000(message.max.bytes in kafka), Message more than 1000000 byes will be dropped.
- discard_kafka_delivery_failed - default: false - discard the record where Kafka::DeliveryFailed occurred
- monitoring_list - default: [] - library to be used to monitor. statsd and datadog are supported
kafka_buffered has two additional parameters:
- kafka_agg_max_bytes - default: 4096 - Maximum value of total message size to be included in one batch transmission.
- kafka_agg_max_messages - default: nil - Maximum number of messages to include in one batch transmission.
Note: Java based Kafka client uses murmur2 as partitioner function by default. If you want to use same partitioning behavior with fluent-plugin-kafka, change it to murmur2 instead of crc32. Note that for using murmur2 hash partitioner function, you must install digest-murmurhash gem.
This plugin uses ruby-kafka producer for writing data. For performance and reliability concerns, use kafka_bufferd output instead. This is mainly for testing.
<match app.**>
@type kafka
# Brokers: you can choose either brokers or zookeeper.
brokers <broker1_host>:<broker1_port>,<broker2_host>:<broker2_port>,.. # Set brokers directly
zookeeper <zookeeper_host>:<zookeeper_port> # Set brokers via Zookeeper
zookeeper_path <broker path in zookeeper> :default => /brokers/ids # Set path in zookeeper for kafka
default_topic (string) :default => nil
default_partition_key (string) :default => nil
default_message_key (string) :default => nil
output_data_type (json|ltsv|msgpack|attr:<record name>|<formatter name>) :default => json
output_include_tag (bool) :default => false
output_include_time (bool) :default => false
exclude_topic_key (bool) :default => false
exclude_partition_key (bool) :default => false
partitioner_hash_function (enum) (crc32|murmur2) :default => 'crc32'
# ruby-kafka producer options
max_send_retries (integer) :default => 1
required_acks (integer) :default => -1
ack_timeout (integer) :default => nil (Use default of ruby-kafka)
compression_codec (string) :default => nil (No compression. Depends on ruby-kafka: https://github.com/zendesk/ruby-kafka#compression)
max_buffer_size (integer) :default => nil (Use default of ruby-kafka)
max_buffer_bytesize (integer) :default => nil (Use default of ruby-kafka)
</match>
This plugin also supports ruby-kafka related parameters. See Buffered output plugin section.
Note: Java based Kafka client uses murmur2 as partitioner function by default. If you want to use same partitioning behavior with fluent-plugin-kafka, change it to murmur2 instead of crc32. Note that for using murmur2 hash partitioner function, you must install digest-murmurhash gem.
This plugin uses rdkafka instead of ruby-kafka for kafka client.
You need to install rdkafka gem.
# rdkafka is C extension library. Need to install development tools like ruby-devel, gcc and etc
# for v0.12 or later
$ gem install rdkafka --no-document
# for v0.11 or earlier
$ gem install rdkafka -v 0.6.0 --no-document
rdkafka2 is for fluentd v1.0 or later.
<match app.**>
@type rdkafka2
brokers <broker1_host>:<broker1_port>,<broker2_host>:<broker2_port>,.. # Set brokers directly
topic_key (string) :default => 'topic'
default_topic (string) :default => nil
partition_key (string) :default => 'partition'
partition_key_key (string) :default => 'partition_key'
message_key_key (string) :default => 'message_key'
default_topic (string) :default => nil
use_default_for_unknown_topic (bool) :default => false
use_default_for_unknown_partition_error (bool) :default => false
default_partition_key (string) :default => nil
default_message_key (string) :default => nil
exclude_topic_key (bool) :default => false
exclude_partition_key (bool) :default => false
discard_kafka_delivery_failed (bool) :default => false (No discard)
discard_kafka_delivery_failed_regex (regexp) :default => nil (No discard)
use_event_time (bool) :default => false
# same with kafka2
headers (hash) :default => {}
headers_from_record (hash) :default => {}
record_key (string) :default => nil
<format>
@type (json|ltsv|msgpack|attr:<record name>|<formatter name>) :default => json
</format>
# Optional. See https://docs.fluentd.org/v/1.0/configuration/inject-section
<inject>
tag_key tag
time_key time
</inject>
# See fluentd document for buffer section parameters: https://docs.fluentd.org/v/1.0/configuration/buffer-section
# Buffer chunk key should be same with topic_key. If value is not found in the record, default_topic is used.
<buffer topic>
flush_interval 10s
</buffer>
# You can set any rdkafka configuration via this parameter: https://github.com/edenhill/librdkafka/blob/master/CONFIGURATION.md
rdkafka_options {
"log_level" : 7
}
# rdkafka2 specific parameters
# share kafka producer between flush threads. This is mainly for reducing kafka operations like kerberos
share_producer (bool) :default => false
# Timeout for polling message wait. If 0, no wait.
rdkafka_delivery_handle_poll_timeout (integer) :default => 30
# If the record size is larger than this value, such records are ignored. Default is no limit
max_send_limit_bytes (integer) :default => nil
# The maximum number of enqueueing bytes per second. It can reduce the
# load of both Fluentd and Kafka when excessive messages are attempted
# to send. Default is no limit.
max_enqueue_bytes_per_second (integer) :default => nil
</match>
rdkafka2 supports discard_kafka_delivery_failed_regex parameter:
discard_kafka_delivery_failed_regex- default: nil - discard the record where the Kafka::DeliveryFailed occurred and the emitted message matches the given regex pattern, such as/unknown_topic/.
If you use v0.12, use rdkafka instead.
<match kafka.**>
@type rdkafka
default_topic kafka
flush_interval 1s
output_data_type json
rdkafka_options {
"log_level" : 7
}
</match>
We got lots of similar questions. Almost cases, this problem happens by version mismatch between ruby-kafka and kafka cluster. See ruby-kafka README for more details: https://github.com/zendesk/ruby-kafka#compatibility
To avoid the problem, there are 2 approaches:
- Upgrade your kafka cluster to latest version. This is better because recent version is faster and robust.
- Downgrade ruby-kafka/fluent-plugin-kafka to work with your older kafka.
- Fork it
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Added some feature') - Push to the branch (
git push origin my-new-feature) - Create new Pull Request