On 11 May 2012 22:30, Dan Berindei <[email protected]> wrote: > On Fri, May 11, 2012 at 7:23 PM, Sanne Grinovero <[email protected]> wrote: >> On 11 May 2012 16:37, Galder Zamarreño <[email protected]> wrote: >>> Quickly tried this and caused no issues: >>> https://github.com/galderz/infinispan/commit/7718926e5a4a6763506250362d7bd5cbdccd2931 >> >> Looks good! I'm sure this doesn't solve all future migration problems, >> but if we could keep this kind of tricks around it should improve >> odds. >> IMHO, this is a kind of sensitivity that we should apply across all >> areas (not just flags). >> > > Looks interesting, but then you have the opposite problem: not all new > flags can be ignored, so you need a way to specify that a new flag is > "required". E.g. if we had just added a ZERO_LOCK_ACQUISITION_TIMEOUT > flag then the client would be expecting spurious failures, but not > extra long delays.
You're right - but did you read the conversation on github? We already pointed this out, still I believe we should have an option to ignore unknown flags if/when/exclusively we think the migration is safe: we should be able to tell after the fact, possibly even write migration tests, but can't predict the future. We could also use a single bit in the externalized representation of a flag to mean "safe to be ignored" for any flag, but I'm not sure that all cases would be black/white .. more likely it will depend on use case or actual configuration. >> On a totally different page, why are we serializing Flags one-by-one ? >> We mostly need to serialize EnumSets right? >> An EnumSet can be encoded by using the bits of a couple of bytes. >> Three bytes looks like enough for all our needs.. we could even be >> clever and reserve a special Externalizer-ID for the empty set, to >> avoid 3 bytes where none are needed. >> While currently we need an integer (4 bytes) to encode the header for >> "EnumSet", plus (4 bytes header + 1 byte value) * each flag -> a lot. >> > > RiverMarshaller already has an optimization for the empty set: > https://github.com/dmlloyd/jboss-marshalling/blob/master/river/src/main/java/org/jboss/marshalling/river/RiverMarshaller.java#L613 That code makes perfectly sense in a general purpose use case, but it still needs to serialize the Class definition: we can avoid that, so we should! > I'm not sure why it doesn't encode each element as a bit, it might be > to keep wire compatibility when the order of values in an enum > changes. That's a safe behaviour, expected for a default use case. But if we decide to add the UNKNOWN flag, we could use bitsets. > However, because there is only one EnumSet for all Enum types, a > hypothetical EnumSetExternalizer also needs to write the name of the > enum class - if we wanted to serialize EnumSet<Flag> in 2 bytes then > we'd need to make the transformation in ReplicableCommandExternalizer. > > Cheers > Dan > > _______________________________________________ > infinispan-dev mailing list > [email protected] > https://lists.jboss.org/mailman/listinfo/infinispan-dev _______________________________________________ infinispan-dev mailing list [email protected] https://lists.jboss.org/mailman/listinfo/infinispan-dev
