[GitHub] [geode] demery-pivotal opened a new pull request #5861: GEODE-8404: Make tests use AvailablePortHelper, not AvailablePort

[GitBox <gi...@apache.org>]

demery-pivotal opened a new pull request #5861:
URL: https://github.com/apache/geode/pull/5861


   Make nearly all tests use AvailablePortHelper instead of AvailablePort
   to obtain ports. See the rationale below.
   
   Also: Remove unused methods from AvailablePort.
   
   Rationale:
   
   AvailablePort is inherently risky as a source of ports for tests.
   Each "get available port" method obtains candidate port numbers from the
   desired range by randomly sampling with replacement. This means that
   multiple calls can return the same port number if the port is not put
   into use between calls.
   
   Some tests failed intermittently because they made multiple calls to
   AvailablePort, received the same port on multiple calls, and unknowingly
   attempted bind multiple sockets to the same port number, resulting in a
   BindException. See GEODE-6622 for examples.
   
   AvailablePortHelper does not have this problem. It obtains candidate
   port numbers round robin. After returning an available port,
   AvailablePortHelper will not return that port again in that JVM until it
   has tested every other port in the range for availability.
   
   To reduce the chance of different JVMs selecting each other's ports,
   AvailablePortHelper selects a random starting point for its round robin
   search in each JVM.
   
   For distributed tests, DUnit further arranges for the
   AvailablePortHelper in each JVM to start its round robin search in a
   distinct place, maximally distant from the starting points of all other
   JVMs. Because AvailablePort selects randomly from the full port range,
   it cannot benefit from this techique.
   
   The problems caused by AvailablePort are rare, but inevitable, with a
   frequency determined by the total size of the port range. An upcoming
   change will make the available port range much smaller (~400 ports
   instead of the current ~10000 ports), which will greatly increase the
   frequency of this problem. But the problem exists now, and results in
   intermittent BindExceptions.


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[GitHub] [geode] demery-pivotal merged pull request #5861: GEODE-8404: Make tests use AvailablePortHelper, not AvailablePort

[GitBox <gi...@apache.org>]

demery-pivotal merged pull request #5861:
URL: https://github.com/apache/geode/pull/5861


   


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