Implement long_callback Python decorator addressing #218

Clover package Python library added.

Author: okalachev

builder/test/tests.py

@@ -22,6 +22,7 @@
 from led_msgs.srv import SetLEDs
 from led_msgs.msg import LEDStateArray, LEDState
 from aruco_pose.msg import Marker, MarkerArray, Point2D
+from clover import long_callback
 
 import dynamic_reconfigure.client
 

clover/CMakeLists.txt

@@ -53,7 +53,7 @@ find_package(OpenCV ${_opencv_version} REQUIRED
 ## Uncomment this if the package has a setup.py. This macro ensures
 ## modules and global scripts declared therein get installed
 ## See http://ros.org/doc/api/catkin/html/user_guide/setup_dot_py.html
-# catkin_python_setup()
+catkin_python_setup()
 
 ################################################
 ## Declare ROS messages, services and actions ##

clover/setup.py

@@ -0,0 +1,11 @@
+## ! DO NOT MANUALLY INVOKE THIS setup.py, USE CATKIN INSTEAD
+
+from distutils.core import setup
+from catkin_pkg.python_setup import generate_distutils_setup
+
+# fetch values from package.xml
+setup_args = generate_distutils_setup(
+    packages=['clover'],
+    package_dir={'': 'src'})
+
+setup(**setup_args)

clover/src/clover/__init__.py

@@ -0,0 +1,35 @@
+import rospy
+from threading import Thread, Event
+
+def long_callback(fn):
+    """
+    Decorator fixing a rospy issue for long-running topic callbacks, primarily
+    for image processing.
+
+    See: https://github.com/ros/ros_comm/issues/1901.
+
+    Usage example:
+
+    @long_callback
+    def image_callback(msg):
+        # perform image processing
+        # ...
+
+    rospy.Subscriber('main_camera/image_raw', Image, image_callback)
+    """
+    e = Event()
+
+    def thread():
+        while not rospy.is_shutdown():
+            e.wait()
+            e.clear()
+            fn(thread.current_msg)
+
+    thread.current_msg = None
+    Thread(target=thread, daemon=True).start()
+
+    def wrapper(msg):
+        thread.current_msg = msg
+        e.set()
+
+    return wrapper

clover/test/basic.py

@@ -3,6 +3,7 @@
 import pytest
 from mavros_msgs.msg import State
 from clover import srv
+import time
 
 @pytest.fixture()
 def node():
@@ -60,3 +61,18 @@ def wait_print():
 
     t.join()
     assert wait_print.result == 'test'
+
+def test_long_callback():
+    from clover import long_callback
+    from time import sleep
+
+    # very basic test for long_callback
+    @long_callback
+    def cb(i):
+        cb.counter += i
+    cb.counter = 0
+    cb(2)
+    sleep(0.1)
+    cb(3)
+    sleep(1)
+    assert cb.counter == 5