ResponseClassifiers for use with finagle-thrift
request/responses.
Thrift (and ThriftMux) services are a bit unusual in that
there is only a single com.twitter.finagle.Service from Array[Byte]
to Array[Byte] for all the methods of an IDL's service.
Thrift classifiers should be written in terms
of the Scrooge generated request $Service.$Method.Args type and the
method's response type. This is because there is support in Scrooge
and Thrift.newService/newClient
to deserialize the responses into the expected application types
so that classifiers can be written in a normal way.
val classifier: ResponseClassifier = {
case ReqRep(_, Throw(_: RateLimitedException)) => RetryableFailure
case ReqRep(_, Throw(_: NotFoundException)) => NonRetryableFailure
case ReqRep(_, Return(x: Int)) if x == 0=> NonRetryableFailure
case ReqRep(SocialGraph.Follow.Args(a, b), _) if a <= 0 || b <= 0=> NonRetryableFailure
}
ResponseClassifiers for use with
finagle-thriftrequest/responses.Thrift (and ThriftMux) services are a bit unusual in that there is only a single com.twitter.finagle.Service from
Array[Byte]toArray[Byte]for all the methods of an IDL's service.Thrift classifiers should be written in terms of the Scrooge generated request
$Service.$Method.Argstype and the method's response type. This is because there is support in Scrooge andThrift.newService/newClientto deserialize the responses into the expected application types so that classifiers can be written in a normal way.Given an idl:
exception NotFoundException { 1: string reason } exception RateLimitedException { 1: string reason } service SocialGraph { i32 follow(1: i64 follower, 2: i64 followee) throws ( 1: NotFoundException ex, 2: RateLimitedException ex ) }One possible custom classifier would be:
Often times, a good default classifier is ThriftResponseClassifier.ThriftExceptionsAsFailures which treats any Thrift response that deserializes into an Exception as a non-retryable failure.