Fluent Plugin for Amazon Kinesis producing KPL records

Build Status

Before you start...

This is a rewrite of aws-fluent-plugin-kinesis to implement a different shipment method using the KPL aggregation format.

Since this plugin was forked, aws-fluent-plugin-kinesis has undergone considerable development (and improvement). Most notably, the upcoming 2.0 release supports KPL aggregated records using google-protobuf without the overhead of using the KPL: https://github.com/awslabs/aws-fluent-plugin-kinesis/issues/107

However, it still uses msgpack for internal buffering and only uses protobuf when it ships the records, whereas this plugin processes each record as it comes in and ships the result by simple concatenation of the encoded records. This may not be faster, of course - could depend on the overhead of calling the protobuf methods - but most probably is. The discussion below is also still mostly valid, in that the awslabs plugin does not have PutRecord == chunk equivalency, but instead has its own internal retry method.

The basic idea is to have one PutRecord === one chunk. This has a number of advantages:

  • much less complexity in plugin (less CPU/memory)
  • by aggregating, we increase the throughput and decrease the cost
  • since a single chunk either succeeds or fails, we get to use fluentd's more complex/complete retry mechanism (which is also exposed by the monitor plugin; we view this in datadog). The existing retry mechanism had unfortunate issues under heavy load
  • we get ordering within a chunk without having to rely on sequence numbers (though not overall ordering)

However, there are drawbacks:

  • if you're using this as an aggregator, you will need to tune the buffer size on your sources fairly low such that it is less than the low buffer_chunk_limit on the aggregator
  • you have to use a KCL library to ingest
  • you can't use a calculated partition key (based on the record); essentially, you need to use a random partition key


Fluentd output plugin that sends events to Amazon Kinesis.


This plugin is available as the fluent-plugin-kinesis-aggregation gem from RubyGems:

gem install fluent-plugin-kinesis-aggregation

Or, if using td-agent:

td-agent-gem install fluent-plugin-kinesis-aggregation

To install from the source:

git clone https://github.com/atlassian/fluent-plugin-kinesis-aggregation.git
cd fluent-plugin-kinesis-aggregation
bundle install
rake build
rake install

Or, if using td-agent, replace rake install with:

fluent-gem install pkg/fluent-plugin-kinesis-aggregation

Alternatively, you can replace both the rake steps, and directly specify the library path via RUBYLIB:

export RUBYLIB=$RUBYLIB:/path/to/fluent-plugin-kinesis-aggregation/lib


  • Ruby 2.7+
  • Fluentd 1+

If you need td-agent v3 support, use version 0.3.x on rubygems. If you need td-agent v2 support (or fluentd 0.10 or 0.12 support), use the fluentd-v0.12 branch or version 0.2.x on rubygems.

Basic Usage

Here are general procedures for using this plugin:

  1. Install.
  2. Edit configuration
  3. Run Fluentd or td-agent

You can run this plugin with Fluentd as follows:

  1. Install.
  2. Edit configuration file and save it as 'fluentd.conf'.
  3. Then, run fluentd -c /path/to/fluentd.conf

To run with td-agent, it would be as follows:

  1. Install.
  2. Edit configuration file provided by td-agent.
  3. Then, run or restart td-agent.


Here are items for Fluentd configuration file.

To put records into Amazon Kinesis, you need to provide AWS security credentials. If you provide aws_key_id and aws_sec_key in configuration file as below, we use it. You can also provide credentials via environment variables as AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY. Also we support IAM Role for authentication. Please find the AWS SDK for Ruby Developer Guide for more information about authentication. We support all options which AWS SDK for Ruby supports.


Use the word 'kinesis-aggregation'.


Name of the stream to put data.


AWS access key id.


AWS secret key.


IAM Role to be assumed with AssumeRole. Use this option for cross account access.


A unique identifier that is used by third parties when assuming roles in their customers' accounts. Use this option with role_arn for third party cross account access. For details, please see How to Use an External ID When Granting Access to Your AWS Resources to a Third Party.


AWS region of your stream. It should be in form like "us-east-1", "us-west-2". Refer to Regions and Endpoints in AWS General Reference for supported regions.


Proxy server, if any. It should be in form like "http://squid:3128/"


Instead of using a random partition key, used a fixed one. This forces all writes to a specific shard, and if you're using a single thread/process will probably keep event ordering (not recommended - watch out for hot shards!).


Integer. The number of threads to flush the buffer. This plugin is based on Fluentd::Plugin::Output, so we buffer incoming records before emitting them to Amazon Kinesis. You can find the detail about buffering mechanism here. Emitting records to Amazon Kinesis via network causes I/O Wait, so parallelizing emitting with threads will improve throughput.

This option can be used to parallelize writes into the output(s) designated by the output plugin. The default is 1. Also you can use this option with multi workers.

multi workers

This feature is introduced in Fluentd v0.14. Instead of using detach_process, this feature can use as the following system directive. Note that detach_process parameter is removed after using v0.14 Output Plugin API. The default is 1.

  workers 5


Boolean. Enable if you need to debug Amazon Kinesis API call. Default is false.

Configuration examples

Here are some configuration examles. Assume that the JSON object below is coming to with tag 'your_tag'.


Simply putting events to Amazon Kinesis with a partition key

In this example, a value 'foo' will be used as the partition key, then events will be sent to the stream specified in 'stream_name'.

<match your_tag>
type kinesis-aggregation

stream_name YOUR_STREAM_NAME

aws_sec_key YOUR_SECRET_KEY

region us-east-1

fixed_partition_key foo

# You should set the buffer_chunk_limit to substantially less
# than the kinesis 1mb record limit, since we ship a chunk at once.
buffer_chunk_limit 300k

Improving throughput to Amazon Kinesis

The achievable throughput to Amazon Kinesis is limited to single-threaded PutRecord calls, which should be at most around 300kb each. The plugin can also be configured to execute in parallel. The detach_process and num_threads configuration settings control parallelism.

In case of the configuration below, you will spawn 2 processes.

<match your_tag>
type kinesis

stream_name YOUR_STREAM_NAME
region us-east-1

detach_process 2
buffer_chunk_limit 300k

You can also specify a number of threads to put. The number of threads is bound to each individual processes. So in this case, you will spawn 1 process which has 50 threads.

<match your_tag>
type kinesis

stream_name YOUR_STREAM_NAME
region us-east-1

num_threads 50
buffer_chunk_limit 300k

Both options can be used together, in the configuration below, you will spawn 2 processes and 50 threads per each processes.

<match your_tag>
type kinesis

stream_name YOUR_STREAM_NAME
region us-east-1

detach_process 2
num_threads 50
buffer_chunk_limit 300k