Fixes "the connection was closed by the remote peer" error

.travis.yml

@@ -11,6 +11,7 @@ matrix:
     - python: '2.7'
       env:
         - SO_DISABLE_MOCKS: "1"
+        - SO_DISABLE_MOTO_SERVER: "1"
         - SO_S3_URL: "s3://smart-open-py27-benchmark"
         - SO_S3_RESULT_URL: "s3://smart-open-py27-benchmark-results"
 
@@ -19,12 +20,14 @@ matrix:
     - python: '3.6'
       env:
         - SO_DISABLE_MOCKS: "1"
+        - SO_DISABLE_MOTO_SERVER: "1"
         - SO_S3_URL: "s3://smart-open-py36-benchmark"
         - SO_S3_RESULT_URL: "s3://smart-open-py36-benchmark-results"
 
     - python: '3.7'
       env:
         - SO_DISABLE_MOCKS: "1"
+        - SO_DISABLE_MOTO_SERVER: "1"
         - SO_S3_URL: "s3://smart-open-py37-benchmark"
         - SO_S3_RESULT_URL: "s3://smart-open-py37-benchmark-results"
         - BOTO_CONFIG: "/dev/null"
@@ -33,6 +36,7 @@ matrix:
 
 install:
   - pip install --upgrade setuptools
+  - pip install flask
   - pip install .[test]
   - pip install flake8
   - pip freeze
@@ -45,6 +49,9 @@ script:
       unset SO_S3_URL;
       unset SO_S3_RESULT_URL;
     fi
+  - if [[ ${SO_DISABLE_MOTO_SERVER} -ne 1 ]]; then
+      sh -c "moto_server -p5000 2> /dev/null &";
+    fi
   - flake8 --max-line-length=110
   - python setup.py test
   - export SO_S3_URL=$SO_S3_URL/$(python -c 'from uuid import uuid4;print(uuid4())')

smart_open/s3.py

@@ -19,6 +19,8 @@
 
 import smart_open.bytebuffer
 
+from botocore.exceptions import IncompleteReadError
+
 logger = logging.getLogger(__name__)
 
 # Multiprocessing is unavailable in App Engine (and possibly other sandboxes).
@@ -170,27 +172,30 @@ def __init__(self, s3_object, content_length, version_id=None):
         self._object = s3_object
         self._content_length = content_length
         self._version_id = version_id
-        self.seek(0)
+        self._position = 0
+        self._body = None
 
     def seek(self, position):
         """Seek to the specified position (byte offset) in the S3 key.
 
         :param int position: The byte offset from the beginning of the key.
         """
-        self._position = position
-        range_string = make_range_string(self._position)
-        logger.debug('content_length: %r range_string: %r', self._content_length, range_string)
-
         #
         # Close old body explicitly.
-        # When first seek(), self._body is not exist. Catch the exception and do nothing.
+        # When first seek() after __init__(), self._body is not exist.
         #
-        try:
+        if self._body is not None:
             self._body.close()
-        except AttributeError:
-            pass
+        self._body = None
+        self._position = position
+
+    def _load_body(self):
+        """Build a continuous connection with the remote peer starts from the current postion.
+        """
+        range_string = make_range_string(self._position)
+        logger.debug('content_length: %r range_string: %r', self._content_length, range_string)
 
-        if position == self._content_length == 0 or position == self._content_length:
+        if self._position == self._content_length == 0 or self._position == self._content_length:
             #
             # When reading, we can't seek to the first byte of an empty file.
             # Similarly, we can't seek past the last byte.  Do nothing here.
@@ -199,13 +204,27 @@ def seek(self, position):
         else:
             self._body = _get(self._object, self._version_id, Range=range_string)['Body']
 
-    def read(self, size=-1):
-        if self._position >= self._content_length:
-            return b''
+    def _read_from_body(self, size=-1):
         if size == -1:
             binary = self._body.read()
         else:
             binary = self._body.read(size)
+        return binary
+
+    def read(self, size=-1):
+        """Read from the continuous connection with the remote peer."""
+        if self._position >= self._content_length:
+            return b''
+        if self._body is None:
+            # When the first read() after __init__() or seek(), self._body is not exist.
+            self._load_body()
+
+        try:
+            binary = self._read_from_body(size)
+        except IncompleteReadError:
+            # The underlying connection of the self._body was closed by the remote peer.
+            self._load_body()
+            binary = self._read_from_body(size)
         self._position += len(binary)
         return binary
 

smart_open/tests/test_s3.py

@@ -34,6 +34,7 @@
 KEY_NAME = 'test-key'
 WRITE_KEY_NAME = 'test-write-key'
 DISABLE_MOCKS = os.environ.get('SO_DISABLE_MOCKS') == "1"
+DISABLE_MOTO_SERVER = os.environ.get("SO_DISABLE_MOTO_SERVER") == "1"
 
 
 logger = logging.getLogger(__name__)
@@ -104,6 +105,27 @@ def ignore_resource_warnings():
     warnings.filterwarnings("ignore", category=ResourceWarning, message="unclosed.*<ssl.SSLSocket.*>")  # noqa
 
 
+@unittest.skipIf(DISABLE_MOTO_SERVER, 'The test case needs a Moto server running on the local 5000 port.')
+class SeekableRawReaderTest(unittest.TestCase):
+
+    def setUp(self):
+        self._local_resource = boto3.resource('s3', endpoint_url='http://localhost:5000')
+        self._local_resource.Bucket(BUCKET_NAME).create()
+        self._local_resource.Object(BUCKET_NAME, KEY_NAME).put(Body=b'123456')
+
+    def tearDown(self):
+        self._local_resource.Object(BUCKET_NAME, KEY_NAME).delete()
+        self._local_resource.Bucket(BUCKET_NAME).delete()
+
+    def test_read_from_a_closed_body(self):
+        obj = self._local_resource.Object(BUCKET_NAME, KEY_NAME)
+        content_length = obj.content_length
+        reader = smart_open.s3.SeekableRawReader(obj, content_length)
+        self.assertEqual(reader.read(1), b'1')
+        reader._body.close()
+        self.assertEqual(reader.read(2), b'23')
+
+
 @maybe_mock_s3
 class SeekableBufferedInputBaseTest(unittest.TestCase):
     def setUp(self):