Added UP/DOWN status metric of the decision engine

src/decisionengine/framework/engine/DecisionEngine.py

@@ -65,7 +65,7 @@
 QUERY_TOOL_HISTOGRAM = Histogram("de_client_query_duration_seconds", "Time to run de-client --query", ["product"])
 METRICS_HISTOGRAM = Histogram("de_client_metrics_duration_seconds", "Time to run de-client --status")
 WORKERS_COUNT = Gauge("de_workers_total", "Number of workers started by the Decision Engine")
-
+DE_STATUS = Gauge("de_status", "Status of Decision Engine server")
 
 class StopState(enum.Enum):
     NotFound = 1
@@ -944,6 +944,7 @@ def _start_de_server(server):
         start_channels_thread.start()
 
         server.get_logger().debug("running _start_de_server: step serve_forever")
+        DE_STATUS.set(1) 
         server.serve_forever(
             poll_interval=1
         )  # Once per second is sufficient, given the amount of work done in the service actions.
@@ -961,6 +962,7 @@ def _start_de_server(server):
         raise __e
     finally:
         start_channels_thread.join(None)
+        DE_STATUS.set(0) 
         server.shutdown_complete.wait()
         r = redis.Redis.from_url(server.broker_url)
         while _requests_in_flight(r, server.exchange.name):