Move trace_id to 64 bits

ujson doesn't support the serialization of long integers (it fails
if it is bigger than 2 ** 63).

Author: LotharSee

ddtrace/compat.py

@@ -21,12 +21,9 @@
 
 
 try:
-    import ujson as json
+    import simplejson as json
 except ImportError:
-    try:
-        import simplejson as json
-    except ImportError:
-        import json
+    import json
 
 def iteritems(obj, **kwargs):
     func = getattr(obj, "iteritems", None)

ddtrace/sampler.py

@@ -2,15 +2,13 @@
 
 Any `sampled = False` trace won't be written, and can be ignored by the instrumentation.
 """
-
 import logging
 import array
 import threading
 
-from .span import MAX_TRACE_ID
-
 log = logging.getLogger(__name__)
 
+MAX_TRACE_ID = 2 ** 64
 
 class AllSampler(object):
     """Sampler sampling all the traces"""

ddtrace/span.py

@@ -274,8 +274,6 @@ def __repr__(self):
             self.name,
         )
 
-MAX_TRACE_ID = 2 ** 63
 def _new_id():
-    """Generate a random trace_id"""
-    return random.getrandbits(63)
-
+    """Generate a random trace_id or span_id"""
+    return random.getrandbits(64)