On May 15, 2012, at 10:52 AM, Dan Berindei wrote: > On Tue, May 15, 2012 at 10:44 AM, Galder Zamarreño <[email protected]> wrote: >> >> On May 11, 2012, at 11:30 PM, Dan Berindei 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. >> >> Hmmm, I disagree. If you're adding a new flag, say in 5.2, and you expect a >> node that runs 5.0 to deal with it properly, really, what you need to be >> doing is implementing that flag in 5.0. >> > > Well, 5.0 is already out there, so modifying it is not an option.
You can always release a 5.0.x :), and I'm pretty sure we might have to do some micro releases to make rolling upgrades work. > What we can do is ensure that the clients see the incompatibility in > their testing environment and don't use two versions in production > without being aware of the problem. > >> We want: >> - if an old client encounters a new/unknown marshalled value, to not blow up >> and log a WARN. >> - if an old client is expected to react to a to a new/unknown marshalled >> value in the way new versions deal with it, it'll need to implement it. >> >> We don't want: >> - old client to 'blow up in flames' when they encounter new/unknown options, >> since this causes problems with potential rolling upgrades. >> > > I think there are situations where two versions really are > incompatible and we really should "blow up in flames". Any blowing up in flames would stop rolling upgrades from working, so find me a real example of this first and try to understand how rolling upgrade would work in that scenario... > I'm not saying that's justified in all cases or even in the majority > of cases, but I'm pretty sure it's not going to be 0% either. > >>> >>>> 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 >>> >>> 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. >> >> David? >> >>> 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. >> >> Not necessarily. I think we should do what Sanne suggests but manually in >> the Flag.Externalizer class, since that's tied to the Flag type. >> >> Within it, we can replicate what an enum set does for marshalling. We >> already have such code in the Hot Rod server/client (that's how we handle >> flags there - completely forgot about it when I wrote Flag.Externalizer), so >> shouldn't be a biggie. >> > > The call stack looks like this: ReplicableCommandExternalizer -> > EnumSet externalizer (in RiverMarshaller) -> Flag.Externalizer. > You can't change how the EnumSet is serialized in Flag.Externalizer, > you have to modify either the EnumSet externalizer (e.g. by writing a > new FlagSet class) or ReplicableCommandExternalizer. Writing a new FlagSet class is my fav. Easy to do and easy to resgister in the ext table. > > The HotRod flags are serialized directly in Codec10.writeHeader, which > is the equivalent of ReplicableCommandExternalizer.writeCommandHeader. > > _______________________________________________ > infinispan-dev mailing list > [email protected] > https://lists.jboss.org/mailman/listinfo/infinispan-dev -- Galder Zamarreño Sr. Software Engineer Infinispan, JBoss Cache _______________________________________________ infinispan-dev mailing list [email protected] https://lists.jboss.org/mailman/listinfo/infinispan-dev
