receive_event: Make it optionally semi-nonblocking

Right now receive_event is blocking, and even on receiving
keep alive it stay inside its own busy loop, which makes
impossible to implement proper scheduling, watchdogs,
health monitoring.
We make optional parameter, where on keep alive message,
(sent each 45 sec by kernelci-api) it will return None.
We keep backward compatible defaults, as lot of code is not
expecting None in return.

Signed-off-by: Denys Fedoryshchenko <[email protected]>

Author: nuclearcat

kernelci/api/helper.py

@@ -64,9 +64,13 @@ def unsubscribe_filters(self, sub_id):
             self._filters.pop(sub_id)
         self.api.unsubscribe(sub_id)
 
-    def receive_event_data(self, sub_id):
-        """Receive CloudEvent from Pub/Sub and return its data payload"""
-        return self.api.receive_event(sub_id).data
+    def receive_event_data(self, sub_id, keep_alive=False):
+        """Receive CloudEvent from Pub/Sub and return its data payload
+        If keep_alive is True, on receiving an "keep-alive" event,
+        such as "BEEP" ping, it will return None instead of the data.
+        Without this, it will block until an event is received.
+        """
+        return self.api.receive_event(sub_id, keep_alive=keep_alive).data
 
     def pop_event_data(self, list_name):
         """Receive CloudEvent from Redis list and return its data payload"""

kernelci/api/latest.py

@@ -163,7 +163,7 @@ def unsubscribe(self, sub_id: int):
     def send_event(self, channel: str, data):
         self._post('/'.join(['publish', channel]), data)
 
-    def receive_event(self, sub_id: int):
+    def receive_event(self, sub_id: int, keep_alive: bool = False):
         path = '/'.join(['listen', str(sub_id)])
         while True:
             resp = self._get(path)
@@ -172,6 +172,10 @@ def receive_event(self, sub_id: int):
                 continue
             event = from_json(data)
             if event.data == 'BEEP':
+                if keep_alive:
+                    # If keep_alive is True, return None
+                    # for "keep-alive" events
+                    return None
                 continue
             return event