Re: [jbosscache-dev] Critical CacheMarshaller issue

On 8 Nov 2007, at 03:00, Jason T. Greene wrote: > Manik Surtani wrote: >> A nasty bug, spotted by someone in the user forum (initially as a CCE) >> http://jira.jboss.org/jira/browse/JBCACHE-1211 >> Copying from the JIRA: >> "This is a nasty. What started life as an optimisation for certain >> types of objects in a marshalled stream (Fqn, GlobalTransactio, >> String and Serializable) has become a major limitation in that a >> single stream can only hold up to 32767 different (not equal()) >> instances of such objects. >> Basically the optimisation was, for example, instead of writing >> "hello" to a stream twice, just write it once and use a reference for >> all subsequent times. Unfortunately this reference was encoded as a >> short, hence the limitation of 32767. >> Fixing this will definitely break wire compatibility with JBoss Cache >> 2.0.0, although JBC does allow backward compatibility by specifying >> replication version in your configuration, thanks to the >> VersionAwareMarshaller. " >> So I guess this mandates the need for a CacheMarshaller210. The >> question is how do we fix this. The obvious thing is to replace the >> short references with integers. The 2 ^ 31 - 1 number of references >> this would allow should be plenty! The drawback though, is larger >> streams. 4-byte refs instead of 2-byte refs can be an unnecessary >> overhead especially if objects aren't repeated much. > > I wouldn't worry too much about the extra bytes. However, you could > maintain backwards compatibility, and save the 2 bytes, by stealing > the sign bit on the short. If byte1 & 0x80 then read 3 more bytes, > else read only 1 more. > Still wouldn't help if you needed a million Strings in a collection. :-)