[core] add backward compatibility for pin.service

Author: Emanuele Palazzetti

ddtrace/pin.py

@@ -24,11 +24,10 @@ class Pin(object):
         >>> pin = Pin.override(conn, service="user-db")
         >>> conn = sqlite.connect("/tmp/image.db")
     """
-    __slots__ = ['app', 'app_type', 'service', 'tags', 'tracer', '_target', '_config', '_initialized']
+    __slots__ = ['app', 'app_type', 'tags', 'tracer', '_target', '_config', '_initialized']
 
     def __init__(self, service, app=None, app_type=None, tags=None, tracer=None, _config=None):
         tracer = tracer or ddtrace.tracer
-        self.service = service
         self.app = app
         self.app_type = app_type
         self.tags = tags
@@ -37,8 +36,17 @@ def __init__(self, service, app=None, app_type=None, tags=None, tracer=None, _co
         # keep the configuration attribute internal because the
         # public API to access it is not the Pin class
         self._config = _config or {}
+        # [Backward compatibility]: service argument updates the `Pin` config
+        self._config['service_name'] = service
         self._initialized = True
 
+    @property
+    def service(self):
+        """Backward compatibility: accessing to `pin.service` returns the underlying
+        configuration value.
+        """
+        return self._config['service_name']
+
     def __setattr__(self, name, value):
         if getattr(self, '_initialized', False) and name is not '_target':
             raise AttributeError("can't mutate a pin, use override() or clone() instead")

tests/test_instance_config.py

@@ -1,6 +1,6 @@
 from unittest import TestCase
 
-from nose.tools import ok_
+from nose.tools import eq_, ok_
 
 from ddtrace import config
 from ddtrace.pin import Pin
@@ -47,3 +47,33 @@ def test_configuration_override_instance(self):
         cfg['distributed_tracing'] = False
         ok_(config.get_from(self.Klass)['distributed_tracing'] is True)
         ok_(config.get_from(instance)['distributed_tracing'] is False)
+
+    def test_service_name_for_pin(self):
+        # ensure for backward compatibility that changing the service
+        # name via the Pin object also updates integration config
+        Pin(service='intake').onto(self.Klass)
+        instance = self.Klass()
+        cfg = config.get_from(instance)
+        eq_(cfg['service_name'], 'intake')
+
+    def test_service_attribute_priority(self):
+        # ensure the `service` arg has highest priority over configuration
+        # for backward compatibility
+        global_config = {
+            'service_name': 'primary_service',
+        }
+        Pin(service='service', _config=global_config).onto(self.Klass)
+        instance = self.Klass()
+        cfg = config.get_from(instance)
+        eq_(cfg['service_name'], 'service')
+
+    def test_configuration_copy(self):
+        # ensure when a Pin is created, it copies the given configuration
+        global_config = {
+            'service_name': 'service',
+        }
+        Pin(service='service', _config=global_config).onto(self.Klass)
+        instance = self.Klass()
+        cfg = config.get_from(instance)
+        cfg['service_name'] = 'metrics'
+        eq_(global_config['service_name'], 'service')