Renames Source/Reader classes for native sources/readers.

This makes it clear that these should not be sub-classed by users.

----Release Notes----
[]
-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=120172996

Author: chamikaramj

google/cloud/dataflow/io/bigquery.py

@@ -264,7 +264,7 @@ def _parse_table_reference(table, dataset=None, project=None):
 # BigQuerySource, BigQuerySink.
 
 
-class BigQuerySource(iobase.Source):
+class BigQuerySource(iobase.NativeSource):
   """A source based on a BigQuery table."""
 
   def __init__(self, table=None, dataset=None, project=None, query=None,
@@ -444,7 +444,7 @@ def writer(self, test_bigquery_client=None, buffer_size=None):
 # BigQueryReader, BigQueryWriter.
 
 
-class BigQueryReader(iobase.SourceReader):
+class BigQueryReader(iobase.NativeSourceReader):
   """A reader for a BigQuery source."""
 
   def __init__(self, source, test_bigquery_client=None):

google/cloud/dataflow/io/fileio.py

@@ -56,7 +56,7 @@ def _gcs_file_copy(from_path, to_path, encoding=''):
 # TextFileSource, TextFileSink.
 
 
-class TextFileSource(iobase.Source):
+class TextFileSource(iobase.NativeSource):
   """A source for a GCS or local text file.
 
   Parses a text file as newline-delimited elements, by default assuming
@@ -250,7 +250,7 @@ def __eq__(self, other):
 # TextFileReader, TextMultiFileReader.
 
 
-class TextFileReader(iobase.SourceReader):
+class TextFileReader(iobase.NativeSourceReader):
   """A reader for a text file source."""
 
   def __init__(self, source):
@@ -347,7 +347,7 @@ def request_dynamic_split(self, dynamic_split_request):
       return
 
 
-class TextMultiFileReader(iobase.SourceReader):
+class TextMultiFileReader(iobase.NativeSourceReader):
   """A reader for a multi-file text source."""
 
   def __init__(self, source):

google/cloud/dataflow/io/iobase.py

@@ -51,11 +51,17 @@ def _dict_printable_fields(dict_object, skip_fields):
                  'compression_type']
 
 
-class Source(object):
-  """Generic source."""
+class NativeSource(object):
+  """A source implemented by Dataflow service.
+
+  This class is to be only inherited by sources natively implemented by Cloud
+  Dataflow service, hence should not be sub-classed by users.
+
+  This class is deprecated and should not be used to define new sources.
+  """
 
   def reader(self):
-    """Returns a SourceReader instance associated with this source."""
+    """Returns a NativeSourceReader instance associated with this source."""
     raise NotImplementedError
 
   def __repr__(self):
@@ -65,8 +71,8 @@ def __repr__(self):
                                               _minor_fields)))
 
 
-class SourceReader(object):
-  """A generic reader for a source."""
+class NativeSourceReader(object):
+  """A reader for a source implemented by Dataflow service."""
 
   def __enter__(self):
     """Opens everything necessary for a reader to function properly."""
@@ -98,12 +104,13 @@ def request_dynamic_split(self, dynamic_split_request):
     """Attempts to split the input in two parts.
 
     The two parts are named the "primary" part and the "residual" part. The
-    current 'SourceReader' keeps processing the primary part, while the
+    current 'NativeSourceReader' keeps processing the primary part, while the
     residual part will be processed elsewhere (e.g. perhaps on a different
     worker).
 
     The primary and residual parts, if concatenated, must represent the
-    same input as the current input of this 'SourceReader' before this call.
+    same input as the current input of this 'NativeSourceReader' before this
+    call.
 
     The boundary between the primary part and the residual part is
     specified in a framework-specific way using 'DynamicSplitRequest' e.g.,
@@ -127,7 +134,7 @@ def request_dynamic_split(self, dynamic_split_request):
 
     Returns:
       'None' if the 'DynamicSplitRequest' cannot be honored (in that
-      case the input represented by this 'SourceReader' stays the same),
+      case the input represented by this 'NativeSourceReader' stays the same),
       or a 'DynamicSplitResult' describing how the input was split into a
       primary and residual part.
     """
@@ -139,7 +146,7 @@ def request_dynamic_split(self, dynamic_split_request):
 
 
 class ReaderProgress(object):
-  """A representation of how far a SourceReader has read through the source."""
+  """A representation of how far a NativeSourceReader has read."""
 
   def __init__(self, position=None, percent_complete=None, remaining_time=None):
 
@@ -179,7 +186,7 @@ def remaining_time(self):
 
 
 class ReaderPosition(object):
-  """A representation of position in an iteration through a 'SourceReader'."""
+  """A representation of position in an iteration of a 'NativeSourceReader'."""
 
   def __init__(self, end=None, key=None, byte_offset=None, record_index=None,
                shuffle_position=None, concat_position=None):
@@ -231,7 +238,7 @@ def __init__(self, index, position):
 
 
 class DynamicSplitRequest(object):
-  """Specifies how 'SourceReader.request_dynamic_split' should split the input.
+  """Specifies how 'NativeSourceReader.request_dynamic_split' should split.
   """
 
   def __init__(self, progress):
@@ -291,9 +298,6 @@ def Write(self, o):  # pylint: disable=invalid-name
 class RangeTracker(object):
   """A thread-safe helper object for implementing dynamic work rebalancing.
 
-  ``RangeTracker`` can be used for implementing dynamic work rebalancing in
-  position-based subclasses of ``iobase.SourceReader``.
-
   **Usage of the RangeTracker class hierarchy**
 
   The ``RangeTracker`` class should not be used per se---all users should use

google/cloud/dataflow/io/pubsub.py

@@ -23,7 +23,7 @@
 from google.cloud.dataflow.io import iobase
 
 
-class PubSubSource(iobase.Source):
+class PubSubSource(iobase.NativeSource):
   """Source for reading from a given Cloud Pub/Sub topic.
 
   Attributes:

google/cloud/dataflow/pipeline_test.py

@@ -18,7 +18,7 @@
 import logging
 import unittest
 
-from google.cloud.dataflow.io.iobase import Source
+from google.cloud.dataflow.io.iobase import NativeSource
 from google.cloud.dataflow.pipeline import Pipeline
 from google.cloud.dataflow.pipeline import PipelineOptions
 from google.cloud.dataflow.pipeline import PipelineVisitor
@@ -35,7 +35,7 @@
 from google.cloud.dataflow.transforms.util import assert_that, equal_to
 
 
-class FakeSource(Source):
+class FakeSource(NativeSource):
   """Fake source returning a fixed list of values."""
 
   class _Reader(object):

google/cloud/dataflow/worker/concat_reader.py

@@ -23,7 +23,7 @@
 from google.cloud.dataflow.io import iobase
 
 
-class ConcatSource(iobase.Source):
+class ConcatSource(iobase.NativeSource):
   """A wrapper source class for ConcatReader."""
 
   def __init__(self, sub_sources):
@@ -36,7 +36,7 @@ def __eq__(self, other):
     return self.sub_sources == other.sub_sources
 
 
-class ConcatReader(iobase.SourceReader):
+class ConcatReader(iobase.NativeSourceReader):
   """A reader that reads elements from a given set of encoded sources.
 
   Creates readers for sources lazily, i.e. only when elements

google/cloud/dataflow/worker/concat_reader_test.py

@@ -22,7 +22,7 @@
 from google.cloud.dataflow.worker import concat_reader
 
 
-class TestSource(iobase.Source):
+class TestSource(iobase.NativeSource):
 
   def __init__(
       self, elements, index_to_fail_reading=-1, fail_reader_at_close=False):
@@ -35,7 +35,7 @@ def reader(self):
                       self.fail_reader_at_close)
 
 
-class TestReader(iobase.SourceReader):
+class TestReader(iobase.NativeSourceReader):
 
   def __init__(self, elements, index_to_fail_reading, fail_reader_at_close):
     self.elements = elements

google/cloud/dataflow/worker/inmemory.py

@@ -20,7 +20,7 @@
 from google.cloud.dataflow.io import iobase
 
 
-class InMemorySource(iobase.Source):
+class InMemorySource(iobase.NativeSource):
   """In-memory input source."""
 
   def __init__(
@@ -49,7 +49,7 @@ def reader(self):
     return InMemoryReader(self)
 
 
-class InMemoryReader(iobase.SourceReader):
+class InMemoryReader(iobase.NativeSourceReader):
   """A reader for in-memory source."""
 
   def __init__(self, source):

google/cloud/dataflow/worker/shuffle.py

@@ -306,7 +306,7 @@ def _str_internal(self):
     return '%s on %s' % (self.__class__.__name__, self.key)
 
 
-class ShuffleReaderBase(iobase.SourceReader):
+class ShuffleReaderBase(iobase.NativeSourceReader):
   """A base class for grouped and ungrouped shuffle readers."""
 
   def __init__(self, shuffle_source, reader=None):
@@ -415,7 +415,7 @@ def __iter__(self):
       yield self.value_coder.decode(entry.value)
 
 
-class ShuffleSourceBase(iobase.Source):
+class ShuffleSourceBase(iobase.NativeSource):
   """A base class for grouped and ungrouped shuffle sources."""
 
   def __init__(self, config_bytes, coder, start_position='', end_position=''):

google/cloud/dataflow/worker/windmillio.py

@@ -49,7 +49,7 @@ def reader(self):
     return PubSubWindmillReader(self)
 
 
-class PubSubWindmillReader(iobase.SourceReader):
+class PubSubWindmillReader(iobase.NativeSourceReader):
   """Internal worker Windmill PubSub reader."""
 
   def __init__(self, source):
@@ -259,7 +259,7 @@ def __repr__(self):
     return '<%s %s>' % (self.__class__.__name__, self.key)
 
 
-class WindowingWindmillSource(iobase.Source):
+class WindowingWindmillSource(iobase.NativeSource):
   """Internal worker PubSubSource which reads from Windmill."""
 
   def __init__(self, context, stream_id, coder):
@@ -270,7 +270,7 @@ def reader(self):
     return WindowingWindmillReader(self)
 
 
-class WindowingWindmillReader(iobase.SourceReader):
+class WindowingWindmillReader(iobase.NativeSourceReader):
   """Internal worker Windmill PubSub reader."""
 
   def __init__(self, source):