1 files changed, 84 insertions, 0 deletions
diff --git a/trollius/executor.py b/trollius/executor.py
new file mode 100644
index 0000000..9e7fdd7
--- /dev/null
+++ b/trollius/executor.py
@@ -0,0 +1,84 @@
+from .log import logger
+
+__all__ = (
+    'CancelledError', 'TimeoutError',
+    'FIRST_COMPLETED', 'FIRST_EXCEPTION', 'ALL_COMPLETED',
+    )
+
+# Argument for default thread pool executor creation.
+_MAX_WORKERS = 5
+
+try:
+    import concurrent.futures
+    import concurrent.futures._base
+except ImportError:
+    FIRST_COMPLETED = 'FIRST_COMPLETED'
+    FIRST_EXCEPTION = 'FIRST_EXCEPTION'
+    ALL_COMPLETED = 'ALL_COMPLETED'
+
+    class Future(object):
+        def __init__(self, callback, args):
+            try:
+                self._result = callback(*args)
+                self._exception = None
+            except Exception as err:
+                self._result = None
+                self._exception = err
+            self.callbacks = []
+
+        def cancelled(self):
+            return False
+
+        def done(self):
+            return True
+
+        def exception(self):
+            return self._exception
+
+        def result(self):
+            if self._exception is not None:
+                raise self._exception
+            else:
+                return self._result
+
+        def add_done_callback(self, callback):
+            callback(self)
+
+    class Error(Exception):
+        """Base class for all future-related exceptions."""
+        pass
+
+    class CancelledError(Error):
+        """The Future was cancelled."""
+        pass
+
+    class TimeoutError(Error):
+        """The operation exceeded the given deadline."""
+        pass
+
+    class SynchronousExecutor:
+        """
+        Synchronous executor: submit() blocks until it gets the result.
+        """
+        def submit(self, callback, *args):
+            return Future(callback, args)
+
+        def shutdown(self, wait):
+            pass
+
+    def get_default_executor():
+        logger.error("concurrent.futures module is missing: "
+                     "use a synchrounous executor as fallback!")
+        return SynchronousExecutor()
+else:
+    FIRST_COMPLETED = concurrent.futures.FIRST_COMPLETED
+    FIRST_EXCEPTION = concurrent.futures.FIRST_EXCEPTION
+    ALL_COMPLETED = concurrent.futures.ALL_COMPLETED
+
+    Future = concurrent.futures.Future
+    Error = concurrent.futures._base.Error
+    CancelledError = concurrent.futures.CancelledError
+    TimeoutError = concurrent.futures.TimeoutError
+
+    def get_default_executor():
+        return concurrent.futures.ThreadPoolExecutor(_MAX_WORKERS)