Doug thanks for sharing your knowledge its appreciated
On Tue, Dec 8, 2009 at 9:14 AM, Doug Cutting <cutt...@apache.org> wrote: > john malkovich wrote: > >> so the question is: >> - both "clientHash" and "serverHash" should be replaced with the >> actual hash of the protocol json definitions? >> > > Yes. Note that the hashing is always done by the owner of the protocol > definition, to make it immune from whitespace differences, etc. So the > client and server each compute the hash of their own protocol and use the > hash of the other's as an opaque cache key. > > > - what is the "server protocol"? if client and server are compatible >> dont they both use the same protocol definition? >> > > They might have different versions of a protocol. Messages may have been > added or removed. In general, the only compatibility that's needed is that: > 1. the server's schema has messages whose names match those of the > client's actual requests; > 2. the server's schema has default values for request parameters that the > client does not provide; and > 3. the client's schema has default values for fields of responses that the > server does not provide. > > Only (1) is presently a hard requirement. For (2) and (3) implementations > may fail if they treat missing fields without default values as required, or > might be able to proceed if they can handle these as unset. There's been > some discussion about mandating that such values are required. But even if > that were done then I'm not sure we'd check it at the time of the handshake, > since the client may never send the offending messages. so how is the schema compatibility handled now in Java? Im assuming that Java is the most compliant implementation. Otherwise you would have to count on runtime exceptions to pick up incompatibilities, which is what I think I saw in python implementation (I could be wrong). what am I missing? doing it on handshake sounds like a sure way to avoid runtime exceptions (if they even should be avoided in this case), but yes it does add that constant overhead even in cases where the conflitc never happens. > > > - the "type": ["null", "string"] syntax means that "type" key has >> either "null" or "string" value? >> > > Yes. JSON arrays are used to signify union types. > > Doug > thanks
