Remove backtracking.

This is a fix for https://bugzilla.mozilla.org/show_bug.cgi?id=1248845.
Chunking was introduced to reduce the memory pressure. Since then
some configuration changes have landed that deal with the issue
in a more general way so that chunking should be no longer required.

setup.py

@@ -2,7 +2,7 @@ from distutils.core import setup
 
 setup(name='telemetry-tools',
       description='Utility code to work with Mozilla Telemetry data.',
-      version='1.0.9',
+      version='1.1.0',
       author='Mozilla',
       url='https://github.com/mozilla/telemetry-tools',
       packages=['telemetry', 'telemetry.util'],

telemetry/util/heka_message.py

@@ -18,43 +18,6 @@ from google.protobuf.message import DecodeError
 _record_separator = 0x1e
 
 
-class BacktrackableFile:
-    def __init__(self, stream):
-        self._stream = stream
-        self._buffer = StringIO()
-
-    def read(self, size):
-        buffer_data = self._buffer.read(size)
-        to_read = size - len(buffer_data)
-
-        if to_read == 0:
-            return buffer_data
-
-        stream_data = self._stream.read(to_read)
-        self._buffer.write(stream_data)
-
-        return buffer_data + stream_data
-
-    def close(self):
-        self._buffer.close()
-        if type(self._stream) == boto.s3.key.Key:
-            if self._stream.resp:  # Hack! Connections are kept around otherwise!
-                self._stream.resp.close()
-
-            self._stream.close(True)
-        else:
-            self._stream.close()
-
-    def backtrack(self):
-        buffer = self._buffer.getvalue()
-        index = buffer.find(chr(_record_separator), 1)
-
-        self._buffer = StringIO()
-        if index >= 0:
-            self._buffer.write(buffer[index:])
-            self._buffer.seek(0)
-
-
 class UnpackedRecord():
     def __init__(self, raw, header, message=None, error=None):
         self.raw = raw
@@ -168,7 +131,7 @@ def unpack_string(string, **kwargs):
     return unpack(StringIO(string), **kwargs)
 
 
-def unpack(fin, raw=False, verbose=False, strict=False, backtrack=False, try_snappy=True):
+def unpack(fin, raw=False, verbose=False, strict=False, try_snappy=True):
     record_count = 0
     bad_records = 0
     total_bytes = 0
@@ -184,10 +147,6 @@ def unpack(fin, raw=False, verbose=False, strict=False, backtrack=False, try_sna
             elif verbose:
                 print e
 
-            if backtrack and type(e) == DecodeError:
-                fin.backtrack()
-                continue
-
         if r is None:
             break
 

telemetry/util/test_heka_message.py

@@ -52,28 +52,6 @@ class TestHekaMessage(unittest.TestCase):
                     threw = True
             self.assertEquals(expected_exceptions[t], threw)
 
-    def test_backtracking_with_initial_separator(self):
-        # Test backtracking when the separator appears at the first character
-        w = hm.BacktrackableFile(StringIO("\x1eFOOBAR"))
-        self.assertEquals("\x1eFOOB", w.read(5))
-        w.backtrack()
-        self.assertEquals("AR", w.read(5))
-
-    def test_backtracking_with_mid_separator(self):
-        # Test backtracking when separator was read
-        w = hm.BacktrackableFile(StringIO("FOOBAR\x1eFOOBAR"))
-        self.assertEquals("FOOBAR\x1eFOO", w.read(10))
-        w.backtrack()
-        self.assertEquals("\x1eFOOBAR", w.read(10))
-
-    def test_backtracking_without_separator(self):
-        # Test backtracking when separator wasn't read
-        w = hm.BacktrackableFile(StringIO("FOOBAR\x1eFOOBAR"))
-        self.assertEquals("FOOBA", w.read(5))
-        w.backtrack()
-        self.assertEquals("R\x1eFOO", w.read(5))
-        self.assertEquals("BAR", w.read(5))
-
 
 if __name__ == "__main__":
     unittest.main()