Important Update for Customers Using Ruby Enterprise Edition

We’ve just released version 0.9.5 of the Instrumental Agent Ruby gem.  The primary change in this version addresses a critical flaw we’ve located when using Ruby Enterprise Edition in concert with a preforking application server like Phusion Passenger. 

The bug in question likely originates in Ruby Enterprise Edition’s garbage collector, and causes an interpreter segfault when Phusion Passenger initializes a new application instance for the instance pool. We’ve reached out to the REE development team via their mailing list and hope that we can receive verification of the bug in the near future.  In the meantime, we strongly recommend that all customers using Ruby Enterprise Edition update to this version in order to ensure application stability.

Our goal with the Instrumental Agent was to ensure that your app does not pay any cost – both in response time and in stability – to record essential metrics.  We’re incredibly sorry to all of our customers who may have run afoul of this bug, and we encourage anyone who thinks they may be suffering stability issues in their app while using the Instrumental Agent to contact us at and we’ll help you review your application’s health level.

For more information about the issue, including known indicators of whether or not your app is susceptible to the problem, please visit our Github wiki page.

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