Core: Classify 503 Service Unavailable errors as transient. (#8182)

Also, pin grpcio < 2.0dev. Closes #5410.

Author: tseaver

google/api_core/retry.py

@@ -98,7 +98,9 @@ def if_exception_type_predicate(exception):
 # Pylint sees this as a constant, but it is also an alias that should be
 # considered a function.
 if_transient_error = if_exception_type(
- (exceptions.InternalServerError, exceptions.TooManyRequests)
+ exceptions.InternalServerError,
+ exceptions.TooManyRequests,
+ exceptions.ServiceUnavailable,
 )
 """A predicate that checks if an exception is a transient API error.
 
@@ -107,6 +109,7 @@ def if_exception_type_predicate(exception):
 - :class:`google.api_core.exceptions.InternalServerError` - HTTP 500, gRPC
  ``INTERNAL(13)`` and its subclasses.
 - :class:`google.api_core.exceptions.TooManyRequests` - HTTP 429
+- :class:`google.api_core.exceptions.ServiceUnavailable` - HTTP 503
 - :class:`google.api_core.exceptions.ResourceExhausted` - gRPC
  ``RESOURCE_EXHAUSTED(8)``
 """

setup.py

@@ -39,7 +39,7 @@
  'futures >= 3.2.0; python_version < "3.2"',
 ]
 extras = {
- "grpc": "grpcio >= 1.8.2",
+ "grpc": "grpcio >= 1.8.2, < 2.0dev",
  "grpcgcp": "grpcio-gcp >= 0.2.2",
  "grpcio-gcp": "grpcio-gcp >= 0.2.2",
 }

tests/unit/test_retry.py

@@ -41,6 +41,7 @@ def test_if_exception_type_multiple():
 def test_if_transient_error():
  assert retry.if_transient_error(exceptions.InternalServerError(""))
  assert retry.if_transient_error(exceptions.TooManyRequests(""))
+ assert retry.if_transient_error(exceptions.ServiceUnavailable(""))
  assert not retry.if_transient_error(exceptions.InvalidArgument(""))