Update system monitor when polling Prometheus metrics (#8745)

Author: hendrikmakait

distributed/http/scheduler/prometheus/core.py

@@ -22,6 +22,8 @@ def __init__(self, server: Scheduler):
         self.subsystem = "scheduler"
 
     def collect(self) -> Iterator[GaugeMetricFamily | CounterMetricFamily]:
+        self.server.monitor.update()
+
         yield GaugeMetricFamily(
             self.build_name("clients"),
             "Number of clients connected",

distributed/http/worker/prometheus/core.py

@@ -32,6 +32,7 @@ def __init__(self, server: Worker):
             )
 
     def collect(self) -> Iterator[Metric]:
+        self.server.monitor.update()
         ws = self.server.state
 
         tasks = GaugeMetricFamily(