This is a bug. I've filed an issue and attached a patch that fixes it: https://issues.apache.org/jira/browse/AVRO-832
Please tell me if this fixes things for you. Doug On 05/30/2011 08:06 PM, Yang wrote: > Thanks Doug. > > regarding "adding or removing fields from a returned record type should > work", > this is actually what triggered my investigation at first, and my tests > seem to show that > it's not the case: > > please see the attached schema.tar , and you can see 2 dirs, "1/" is > for server, "2/" is for client. > they are created by slightly modifying the standard 1.5.1 distribution. > to see the demo, you need > to do (please change the "path_to....." params below accordingly ) > > mkdir demo > cd demo > tar xzf path_to_avro-1.5.1-src.tar.gz > mv avro-src-1.5.1 1 > tar xzf path_to_avro-1.5.1-src.tar.gz > mv avro-src-1.5.1 2 > ## the following overrides some files in standard distro > tar xf path_to_schema.tar > cd 1/lang/java/ipc > mvn compile exec:java -Dexec.mainClass=org.apache.avro.SimpleServer &>log & > cd - > cd 2/lang/java/ipc > mvn -Dtest=org.apache.avro.TestSimpleClient test > > > you will see that the test testClientDiffReturnType() fails with > following exception: > ------------------------------------------------------------------------------- > Test set: org.apache.avro.TestSimpleClient > ------------------------------------------------------------------------------- > Tests run: 2, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 0.392 > sec <<< FAILURE! > testClientDiffReturnType(org.apache.avro.TestSimpleClient) Time > elapsed: 0.005 sec <<< ERROR! > java.lang.ClassCastException: org.apache.avro.test.evolution.Kind cannot > be cast to java.lang.CharSequence > at org.apache.avro.test.evolution.TestRecord.put(TestRecord.java:28) > at org.apache.avro.generic.GenericData.setField(GenericData.java:463) > at > org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:166) > at > org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:138) > at > org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:129) > at > org.apache.avro.ipc.specific.SpecificRequestor.readResponse(SpecificRequestor.java:77) > at org.apache.avro.ipc.Requestor.request(Requestor.java:153) > at > org.apache.avro.ipc.specific.SpecificRequestor.invoke(SpecificRequestor.java:55) > at $Proxy8.echo(Unknown Source) > at > org.apache.avro.TestSimpleClient.testClientDiffReturnType(TestSimpleClient.java:111) > at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) > at > sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) > at > sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) > at java.lang.reflect.Method.invoke(Method.java:616) > at > org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44) > at > org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) > at > org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41) > at > org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20) > at > org.junit.runners.BlockJUnit4ClassRunner.runNotIgnored(BlockJUnit4ClassRunner.java:79) > at > org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:71) > at > org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49) > at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193) > at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52) > > > > the above error shows that avro on the client result parsing step tries > to convert the old TestRecord.kind (second field) to the new > TestRecord.extra_field, which is also the second field. so we get an > error. so that's why I say that it seems not to be doing return schema > conversion for me. maybe I need to do something to enable that? > > Thanks a lot > Yang > > On Mon, May 30, 2011 at 12:36 AM, Doug Cutting <[email protected] > <mailto:[email protected]>> wrote: > > On 05/26/2011 10:10 PM, Yang wrote: > > I guess the schema resolution is done only on input params, and not on > > return value? > > The same resolution should be done on return values. For example, > changing the return value from one record to another would not work > (unless you used aliases) but adding or removing fields from a returned > record type should work. > > > incidentally, I found that if I keep the name of an enum type , but > > add new enum values to it (at the end of the value list), and then use > > the enum type as the return > > type of my RPC call, it still works, although strictly speaking, the > > enum type has already changed. but this is probably quite a dangerous > > hack. > > That should not be dangerous. Avro translates enum values so that > adding & removing symbols is permitted. As long as the reader's schema > still has the symbol that the writer sends things should work. > > Doug > >
