RFR: 8006534 CLONE - TestLibrary.getUnusedRandomPort() fails intermittently-doesn't retry enough times (original) (raw)

Darryl Mocek darryl.mocek at oracle.com
Fri Jan 18 23:11:29 UTC 2013

Hi Jim,

I think this change looks fine.  I think it works for our purposes

for now and is a quick and painless change.

The problem as I understand it is that when getUnusedRandomPort is

called and the port returned is FIXED_PORT_MIN (which is rejected), then the code tries again and returns FIXED_PORT_MIN + 1, then +2, etc.
Since FIXED_PORT_MAX - FIXED_PORT_MIN >= numTries, it fails. The fix increases the number of tries. This means when FIXED_PORT_MAX - FIXED_PORT_MIN increases above the current numTries, then we'll need to increase the number of tries again. This probably won't happen for a while as we're trying to decrease the use of fixed ports, not increase them. However, there are a bunch of tests which currently use fixed ports which aren't using TestLibrary, but should be because we can probably convert most or all of them to use a random port. Those we cannot convert should have their fixed ports reserved in TestLibrary.

After some thought, I think we can improve "getting an unused random port by providing a custom SocketImplFactory which will not use ServerSocket (as we open the ServerSocket, get the port number, close the ServerSocket, return the port number...btw, it is unlikely but possible that this port will be grabbed by some other process between the time the ServerSocket is closed and the time the socket is opened by the caller of getUnusedRandomPort, but this may happen with a custom SocketImplFactory anyway) and which only look for ports whicha re not used and which are within a range we want (read outside the FIXED_PORT_* range (and other ranges like < 1024)). I think using a SocketImplFactory will improve the performance and reliability of the tests.

Darryl

On 01/17/2013 12:18 PM, Jim Gish wrote:

Please review http://cr.openjdk.java.net/~jgish/Bug8006534-getUnusedRandomPort-retry-more/ <http://cr.openjdk.java.net/%7Ejgish/Bug8006534-getUnusedRandomPort-retry-more/>

TestLibrary.getUnusedPort() attempts to retry getting an ephemeral port 10 times, which is the current number of ports in the reserved port range. Debugging code added a few weeks back has revealed that intermittent failures in tests using this method are caused when the underlying socket code first returns the first number in the reserved port range. Subsequent retries result in incrementing the port number by one until reaching the max reserved port number, which just happens to correspond to the 10th attempt, and the code then quits trying. The proposed fix (one of many possible alternatives, of course) simply retries for twice the number of ports in the range. Thanks, Jim

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