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Load Generation Tool from Twitter–Iago

Iago is a load generation tool that replays production or synthetic traffic against a given target. Among other things, it differs from other load generation tools in that it attempts to hold constant the transaction rate. For example, if you want to test your service at 100K requests per minute, Iago attempts to achieve that rate.

Because Iago replays traffic, you must specify the source of the traffic. You use a transaction log as the source of traffic, in which each transaction generates a request to your service that your service processes.

Replaying transactions at a fixed rate enables you to study the behavior of your service under an anticipated load. Iago also allows you to identify bottlenecks or other issues that may not be easily observable in a production environment in which your maximum anticipated load occurs only rarely.

Iago understands service requests in the following formats:

  • HTTP
  • Thrift
  • Memcached / Kestrel
  • UDP

Your service is typically an HTTP or Thrift service written in either Scala or Java.

Iago consists of one or more Iago feeders, which reads your transaction source, and one or more Iago servers, which format and deliver requests to the service you want to test. The feeder contains a Poller object, which is responsible for guaranteeing one minute’s worth of transactions in the pipeline to the Iago servers. Metrics are available in logs, and we expect future enhancements to support parsing and visualizing this data.

The Iago servers generate requests to your service. Together, all Iago servers generate the specified number of requests per minute. A Iago server’s RecordProcessor object executes your service and maps the transaction to the format required by your service.

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