Disable default collector metrics

By default, prometheus exports 'process', 'gc' and 'platform' collector
metrics. This information is not useful in our case and introduces some
noise to the metrics, so they have been disabled.

nucypher/utilities/prometheus/metrics.py

@@ -2,6 +2,7 @@
 import json
 from typing import List
 
+from prometheus_client import GC_COLLECTOR, PLATFORM_COLLECTOR, PROCESS_COLLECTOR
 from prometheus_client.core import Timestamp
 from prometheus_client.registry import REGISTRY, CollectorRegistry
 from prometheus_client.utils import floatToGoString
@@ -119,6 +120,11 @@ def start_prometheus_exporter(
     from twisted.web.resource import Resource
     from twisted.web.server import Site
 
+    # Disabling default collector metrics
+    REGISTRY.unregister(GC_COLLECTOR)
+    REGISTRY.unregister(PLATFORM_COLLECTOR)
+    REGISTRY.unregister(PROCESS_COLLECTOR)
+
     metrics_collectors = create_metrics_collectors(ursula)
     # initialize collectors
     for collector in metrics_collectors: