Firehose

This library helps to manage data sending to AWS Firehose dealing with its limitations:

The maximum size of a record sent to Kinesis Data Firehose, before base64-encoding, is 1,000 KiB. The PutRecordBatch operation can take up to 500 records per call or 4 MiB per call, whichever is smaller...the size of each record rounded up to the nearest 5KB

Installation

If available in Hex, the package can be installed by adding firehose to your list of dependencies in mix.exs:

def deps do
  [
    {:firehose, "~> 1.0.0"}
  ]
end

Usage

Create module which will handle callbacks:

defmodule Event.Handler do
  def subscribe(:failed, %Firehose.Batch{} = batch, aws_response) do
    # This callback is triggered when retry count exhausted and batch not delivered.
    # You can add specific logic for this case (write data to queue or database etc) or
    # send metrics to monitoring service
  end

  def subscribe(:completed, %Firehose.Batch{stream: stream, size: batch_size, records: records}) do
    # This callback is triggered after each successfull delivery to Firehose.
    # You can use this callback to send metrics to monitoring service
  end
end

Add appropriate configurations for ex_aws and firehose:

config :ex_aws,
  access_key_id: [{:system, "AWS_ACCESS_KEY_ID"}, :instance_role],
  secret_access_key: [{:system, "AWS_SECRET_ACCESS_KEY"}, :instance_role]

config :firehose, Firehose.Manager,
  handlers: [Event.Handler],
  flush_interval: 1_000, # Flush batches every seconds or on batch size limit
  retries: 5,            # Retry count for failed requests
  serializer: Poison,    # Event serializer: should respond to `encode` and `decode` methods
  delimiter: "\n",       # Add delimiter after each event or add nothing if `false` or `nil` set

Add Firehose.Supervisor to your supervisor tree and thats it. You can emit events to AWS Firehose like this:

Firehose.emit("logs", %{"name" => "pageview", "ua" => "..."})

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/firehose.