Adjust our tracer to work fine with Thrift under Python 2/3.

1. Add an additional pass over our Thrift generated files
   to have code that is compatible with both 2 and 3.
   This requires the six module.
2. Require thrift >= 0.10.0, as this is the first
   release that supports both 2 and 3.
3. Update our util function to coerce strings,
   as the thrift Python library expects us to give it
   strings in its default type (ascii under 2, utf8 under 3).

Author: carlosalberto

Makefile

@@ -57,6 +57,7 @@ test: build
 # the command is run within the LightStep development environment (i.e. the
 # LIGHTSTEP_HOME environment variable is set).
 thrift:
-	docker run -v "$(PWD)/lightstep:/out" -v "$(LIGHTSTEP_HOME)/go/src/crouton:/data" --rm thrift:0.9.2 \
+	docker run -v "$(PWD)/lightstep:/out" -v "$(LIGHTSTEP_HOME)/go/src/crouton:/data" --rm thrift:0.10.0 \
 		thrift -r --gen py -out /out /data/crouton.thrift
+	python-modernize -w lightstep/crouton/
 	rm -rf lightstep/crouton/ReportingService-remote

lightstep/crouton/ReportingService.py

@@ -1,6 +1,7 @@
 """ Utility functions
 """
 import random
+import sys
 import time
 import math
 from . import constants
@@ -52,15 +53,38 @@ def _merge_dicts(*dict_args):
             result.update(dictionary)
     return result if result else None
 
-def _coerce_str(str_or_unicode):
-    if isinstance(str_or_unicode, bytes):
-        return str_or_unicode
-    else:
+if sys.version_info[0] == 2:
+
+    # Coerce to ascii (bytes) under Python 2.
+    def _coerce_str(val):
+        return _coerce_to_bytes(val)
+else:
+
+    # Coerce to utf-8 under Python 3.
+    def _coerce_str(val):
+        return _coerce_to_unicode(val)
+
+def _coerce_to_bytes(val):
+    if isinstance(val, bytes):
+        return val
+    try:
+        return val.encode('utf-8', 'replace')
+    except Exception:
         try:
-            return str_or_unicode.encode('utf-8', 'replace')
+            return bytes(val)
         except Exception:
-            try:
-                return bytes(str_or_unicode)
-            except Exception:
-                # Never let these errors bubble up
-                return '(encoding error)'
+            # Never let these errors bubble up
+            return '(encoding error)'
+
+def _coerce_to_unicode(val):
+    if isinstance(val, str):
+        return val
+    try:
+        return val.decode('utf-8')
+    except Exception:
+        try:
+            return str(val)
+        except Exception:
+            # Never let these errors bubble up
+            return '(encoding error)'
+

lightstep/crouton/ttypes.py

@@ -7,14 +7,13 @@
     long_description='',
     author='LightStep',
     license='',
-    install_requires=['thrift==0.9.2',
+    install_requires=['thrift==0.10.0',
                       'jsonpickle',
                       'six',
                       'basictracer>=2.2,<2.3'],
     tests_require=['pytest',
                    'sphinx',
                    'sphinx-epytext'],
-
     classifiers=[
         'Operating System :: OS Independent',
         'Programming Language :: Python :: 2',

lightstep/util.py

@@ -126,8 +126,7 @@ def check_spans(self, spans):
         """Checks spans' name.
         """
         for i, span in enumerate(spans):
-            name = six.b(str(i)) # name *must* be in bytes/utf-8
-            self.assertEqual(span.span_name, name)
+            self.assertEqual(span.span_name, str(i))
 
     def dummy_basic_span(self, recorder, i):
         return BasicSpan(