Empty for Avro

[juanpedromoreno]

Currently, freestyle.rpc.protocol.Empty is valid for Protocol Buffers, but it is not for Avro.

Using freestyle.rpc.protocol.Empty we can found OOM errors like this one:

[error] (grpc-default-executor-0) java.lang.OutOfMemoryError: GC overhead limit exceeded
[error] java.lang.OutOfMemoryError: GC overhead limit exceeded
[error] 	at org.apache.avro.generic.GenericData.newRecord(GenericData.java:1145)
[error] 	at org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:220)
[error] 	at org.apache.avro.generic.GenericDatumReader.readWithoutConversion(GenericDatumReader.java:174)
[error] 	at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:152)
[error] 	at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:144)
[error] 	at com.sksamuel.avro4s.AvroBinaryInputStream.<init>(AvroInputStream.scala:30)
[error] 	at com.sksamuel.avro4s.AvroInputStream$.binary(AvroInputStream.scala:111)
[error] 	at freestyle.rpc.internal.service.encoders$avro$$anon$2.parse(service.scala:271)
[error] 	at io.grpc.MethodDescriptor.parseRequest(MethodDescriptor.java:283)
[error] 	at io.grpc.internal.ServerCallImpl$ServerStreamListenerImpl.messagesAvailable(ServerCallImpl.java:251)
[error] 	at io.grpc.internal.ServerImpl$JumpToApplicationThreadServerStreamListener$1MessagesAvailable.runInContext(ServerImpl.java:592)
[error] 	at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37)
[error] 	at io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:107)
[error] 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
[error] 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
[error] 	at java.lang.Thread.run(Thread.java:748)
[error] (grpc-default-executor-2) java.lang.OutOfMemoryError: GC overhead limit exceeded
[error] java.lang.OutOfMemoryError: GC overhead limit exceeded
[error] 	at org.apache.avro.generic.GenericData$Record.<init>(GenericData.java:182)
[error] 	at org.apache.avro.generic.GenericData.newRecord(GenericData.java:1145)
[error] 	at org.apache.avro.generic.GenericDatumReader.readRecord(GenericDatumReader.java:220)
[error] 	at org.apache.avro.generic.GenericDatumReader.readWithoutConversion(GenericDatumReader.java:174)
[error] 	at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:152)
[error] 	at org.apache.avro.generic.GenericDatumReader.read(GenericDatumReader.java:144)
[error] 	at com.sksamuel.avro4s.AvroBinaryInputStream.<init>(AvroInputStream.scala:30)
[error] 	at com.sksamuel.avro4s.AvroInputStream$.binary(AvroInputStream.scala:111)
[error] 	at freestyle.rpc.internal.service.encoders$avro$$anon$2.parse(service.scala:271)
[error] 	at io.grpc.MethodDescriptor.parseRequest(MethodDescriptor.java:283)
[error] 	at io.grpc.internal.ServerCallImpl$ServerStreamListenerImpl.messagesAvailable(ServerCallImpl.java:251)
[error] 	at io.grpc.internal.ServerImpl$JumpToApplicationThreadServerStreamListener$1MessagesAvailable.runInContext(ServerImpl.java:592)
[error] 	at io.grpc.internal.ContextRunnable.run(ContextRunnable.java:37)
[error] 	at io.grpc.internal.SerializingExecutor.run(SerializingExecutor.java:107)
[error] 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
[error] 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
[error] 	at java.lang.Thread.run(Thread.java:748)

However, using this type, the issue is gone.

case class EmptyAvro(b: String = "")

We should unify the Empty message for both types of serialization, Protobuf and Avro.