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'ecache' Process Using 99.9% CPU


Article Number: 000001699
Published: July 21, 2016
Categories: Software
A known bug can cause the edge cache process 'ecache' to consume all available CPU
The edge cache functionality of the device is made up of multiple part. The 'ecache' process is the front facing part of the edge cache engine, as it determines exactly how edge cache should behave. The behind the scenes portion called 'squid' is what is in charge of putting items into and taking items out of cache, when required by edge cache. 

Because the ecache process is what directs all the information flow, it is possible in some rare instances to see the ecache process use 99.9% of all available CPU, causing performance problems as well as slow reporting and access on the Exinda appliance.
The ecache process is extremely complex. As a result, it is possible for it to get into a loop, where it keeps atetmpting to do things in a specific order repeatedly, without a required condition to stop. As a result, ecache is stuck using as much CPU as it can waiting for something that will never happen, leading to a perpetual state of CPU use. While this is an extremely rare condition, it can happen during normal use.
Stopping the ecache process, or alternatively disabling edge cache (Configuration > System > Optimization) on the system will stop this problem from occurring. 
The ecache process was redesigned in ExOS v7.4.3 to prevent this exact situation from occurring. Upgrading to 7.4.3 will prevent the edge cache process from consuming all the CPU until it is manually stopped. 
It is normal for ecache (and squid) to use a nominal amount of CPU, depending on the load of the system. This explicitly is referring to a situation when ecache alone is using 99.9% CPU for extended periods of time.
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