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From bugzi...@apache.org
Subject DO NOT REPLY [Bug 12741] - Multithreaded Axis client causes serialization exceptions in Axis service
Date Wed, 25 Sep 2002 20:49:55 GMT
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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=12741

Multithreaded Axis client causes serialization exceptions in Axis service





------- Additional Comments From avolanis@rsasecurity.com  2002-09-25 20:49 -------
Your change had no effect. The reason is that you are still not synchronized at 
one more point of contention. The start of the getSerializerAs method has this 
code:

        // Need to add code to check against mechanisms vector.
        if (share && ser != null) {
            return ser;
        }
        ser = null;

        // Try getting a specialized Serializer
        ser = getSpecialized(mechanismType);

When the "share" flag is true multiple threads may execute this code and 
attempt to "getSpecialized" or "getGeneralPurpose" multiple times when once 
would be enough. In this case you are no longer having the benefit of getting 
something only the first time. This pattern of checking for "== null" and then 
calling the get methods is obvious in many places in this code. I believe you 
either have to put back the synchronized keyword on the getSerializerAs method 
or try to get all instances of "== null" synchronized individually.

As an experiment I put the synchronized keyword at the getSerializerAs method 
and removed it from the individual code blocks. The result was nil. The real 
performance benefit was the application of the test for the boolean "firstCall" 
that was used in the original design before your changes. I believe it 
eliminated a lot more duplicate calls that are obviously happening as a result 
of your changes. Maybe it would be beneficial to examine the code as it was 
before your changes and try to apply the synchronized keyword in the 
appropriate locations if not at the public interface methods.

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