add samples

contrib/opencensus-context/examples/py27.py

@@ -0,0 +1,18 @@
+from opencensus.common.runtime_context import RuntimeContext
+
+RuntimeContext.register_slot('correlation_context', lambda: {})
+
+def hello(name):
+    correlation_context = RuntimeContext.correlation_context.copy()
+    correlation_context['name'] = name
+    RuntimeContext.correlation_context = correlation_context
+
+    print(RuntimeContext)
+
+if __name__ == '__main__':
+    print(RuntimeContext)
+    RuntimeContext.correlation_context['test'] = True
+    print(RuntimeContext)
+    hello('hello')
+    RuntimeContext.clear()
+    print(RuntimeContext)

contrib/opencensus-context/examples/py37.py

@@ -0,0 +1,34 @@
+import asyncio
+
+from opencensus.common.runtime_context import RuntimeContext
+
+RuntimeContext.register_slot('correlation_context', lambda: dict())
+
+async def hello(name):
+    correlation_context = RuntimeContext.correlation_context.copy()
+    correlation_context['name'] = name
+    RuntimeContext.correlation_context = correlation_context
+
+    for i in range(3):
+        print('Hello {} {} {}'.format(
+            name,
+            i,
+            RuntimeContext,
+        ))
+        await asyncio.sleep(0.1)
+
+async def main():
+    print(RuntimeContext)
+    RuntimeContext.correlation_context['test'] = True
+    print(RuntimeContext)
+    await asyncio.gather(
+        hello('foo'),
+        hello('bar'),
+        hello('baz'),
+    )
+    print(RuntimeContext)
+    RuntimeContext.clear()
+    print(RuntimeContext)
+
+if __name__ == '__main__':
+    asyncio.run(main())

contrib/opencensus-context/examples/span.py

@@ -0,0 +1,26 @@
+from opencensus.common.runtime_context import RuntimeContext
+
+RuntimeContext.register_slot('current_span', None)
+
+class Span(object):
+    def __init__(self, name):
+        self.name = name
+        self.parent = RuntimeContext.current_span
+
+    def __repr__(self):
+        return ('{}({})'.format(type(self).__name__, self.name))
+
+    def __enter__(self):
+        RuntimeContext.current_span = self
+
+    def __exit__(self, type, value, traceback):
+        RuntimeContext.current_span = self.parent
+
+if __name__ == '__main__':
+    print(RuntimeContext)
+    with Span('foo'):
+        print(RuntimeContext)
+        with Span('bar'):
+            print(RuntimeContext)
+        print(RuntimeContext)
+    print(RuntimeContext)

contrib/opencensus-context/opencensus/common/runtime_context/__init__.py

@@ -26,25 +26,59 @@ def clear(cls):
     def register_slot(cls, name, default = None):
         raise NotImplementedError  # pragma: NO COVER
 
+    def __init__(self):
+        pass
+
     def __repr__(self):
-        return repr(self._slots)
+        return ('{}({})'
+                .format(
+                    type(self).__name__,
+                    dict((n, self._slots[n].get()) for n in self._slots)
+                ))
+
+    def __getattr__(self, name):
+        if name not in self._slots:
+            raise AttributeError('{} is not a registered context slot'.format(name))
+        slot = self._slots[name]
+        return slot.get()
+
+    def __setattr__(self, name, value):
+        if name not in self._slots:
+            raise AttributeError('{} is not a registered context slot'.format(name))
+        slot = self._slots[name]
+        slot.set(value)
 
 class _TlsRuntimeContext(_RuntimeContext):
     _lock = threading.Lock()
     _slots = {}
-    _tls = threading.local()
 
     class Slot(object):
+        _tls = threading.local()
+
         def __init__(self, name, default):
             self.name = name
-            self.default = default
+            self.default = default if callable(default) else (lambda: default)
+
+        def clear(self):
+            setattr(self._tls, self.name, self.default())
+
+        def get(self):
+            try:
+                return getattr(self._tls, self.name)
+            except AttributeError:
+                value = self.default()
+                self.set(value)
+                return value
+
+        def set(self, value):
+            setattr(self._tls, self.name, value)
 
     @classmethod
     def clear(cls):
         with cls._lock:
             for name in cls._slots:
-                slot = self._slots[name]
-                setattr(cls._tls, name, slot.default)
+                slot = cls._slots[name]
+                slot.clear()
 
     @classmethod
     def register_slot(cls, name, default = None):
@@ -53,20 +87,6 @@ def register_slot(cls, name, default = None):
                 raise ValueError('slot {} already registered'.format(name))
             cls._slots[name] = cls.Slot(name, default)
 
-    def __init__(self):
-        pass
-
-    def __getattr__(self, name):
-        if name in self._slots:
-            slot = self._slots[name]
-            return getattr(self._tls, name, slot.default)
-        raise AttributeError('{} is not a registered context slot'.format(name))
-
-    def __setattr__(self, name, value):
-        if name in self._slots:
-            return setattr(self._tls, name, value)
-        raise AttributeError('{} is not a registered context slot'.format(name))
-
 class _AsyncRuntimeContext(_RuntimeContext):
     _lock = threading.Lock()
     _slots = {}
@@ -76,14 +96,28 @@ def __init__(self, name, default):
             import contextvars
             self.name = name
             self.contextvar = contextvars.ContextVar(name)
-            self.default = default
+            self.default = default if callable(default) else (lambda: default)
+
+        def clear(self):
+            self.contextvar.set(self.default())
+
+        def get(self):
+            try:
+                return self.contextvar.get()
+            except LookupError:
+                value = self.default()
+                self.set(value)
+                return value
+
+        def set(self, value):
+            self.contextvar.set(value)
 
     @classmethod
     def clear(cls):
         with cls._lock:
             for name in cls._slots:
                 slot = cls._slots[name]
-                slot.contextvar.set(slot.default)
+                slot.clear()
 
     @classmethod
     def register_slot(cls, name, default = None):
@@ -92,21 +126,6 @@ def register_slot(cls, name, default = None):
                 raise ValueError('slot {} already registered'.format(name))
             cls._slots[name] = cls.Slot(name, default)
 
-    def __init__(self):
-        pass
-
-    def __getattr__(self, name):
-        if name in self._slots:
-            slot = self._slots[name]
-            return slot.contextvar.get(slot.default)
-        raise AttributeError('{} is not a registered context slot'.format(name))
-
-    def __setattr__(self, name, value):
-        if name in self._slots:
-            slot = self._slots[name]
-            return slot.contextvar.set(value)
-        raise AttributeError('{} is not a registered context slot'.format(name))
-
 RuntimeContext = _TlsRuntimeContext()
 
 if sys.version_info >= (3, 7):