Re: [jbosscache-dev] Critical CacheMarshaller issue

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.