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Sunday, March 28, 2010
Release It! - Chapter 4.3 Cascading Failures
A Cascading Failure is when a crack in one layer triggers a crack in a calling layer. The failure jumps between the layers when bad behavior in the caller gets triggered by a problem in the called layer. Resource pools often get exhaused in this scenario and Integration Points without timeouts is a sure way to cause a Cascading Failure. Cascading Failure are crack accelerators so preventing them is very important. Stop cracks from spanning layers and make sure calling layers can still function even after a lower layer goes dark. Examine your resource pools to ensure they are safe. Safe pools always limit the time a thread can wait to check out a resource. Defend against Cascading Failures by using Circuit Breaker and Timeout patterns. Circuit Breakers prevent call outs to sick layers and Timeouts ensure that you can return from a call to a sick layer.