move comment to javadoc

Author: Daan Hoogland

plugins/integrations/prometheus/src/main/java/org/apache/cloudstack/metrics/PrometheusExporter.java

@@ -18,7 +18,23 @@
 
 public interface PrometheusExporter {
 
+    /**
+     * Update the Prometheus metrics in text format.
+     *
+     * NOTE: capacity data is refreshed independently by {@code AlertManagerImpl}'s own
+     * periodic {@code CapacityChecker} timer. Do NOT force a synchronous
+     * {@code recalculateCapacity()} call here: it spins up a fresh thread pool per host
+     * and per storage pool across ALL zones on every single scrape, so with Z zones a
+     * single Prometheus scrape triggered Z redundant full recalculations. That extra,
+     * uncoordinated load compounds over time and can lead to {@code scrape_duration_seconds}
+     * climbing until a management-server restart.
+     *
+     * @see PrometheusExporterImpl#updateMetrics()
+     */
     void updateMetrics();
 
+    /**
+     * @return the latest Prometheus metrics refreshed by {@link #updateMetrics()}.
+     */
     String getMetrics();
 }

plugins/integrations/prometheus/src/main/java/org/apache/cloudstack/metrics/PrometheusExporterImpl.java

@@ -491,14 +491,6 @@ private void addVMsBySizeMetrics(final List<Item> metricsList, final long dcId,
     public void updateMetrics() {
         final List<Item> latestMetricsItems = new ArrayList<Item>();
         try {
-            // NOTE: capacity data is refreshed independently by AlertManagerImpl's own
-            // periodic CapacityChecker timer (see AlertManagerImpl#start()). Do NOT force a
-            // synchronous recalculateCapacity() here: it spins up a fresh thread pool per host
-            // and per storage pool across ALL zones on every single scrape, so with Z zones a
-            // single Prometheus scrape triggered Z redundant full recalculations. That extra,
-            // uncoordinated load compounds over time (thread churn + overlapping runs with the
-            // timer) and was the cause of https://github.com/apache/cloudstack/issues/13586
-            // (scrape_duration_seconds climbing until a management-server restart).
             for (final DataCenterVO dc : dcDao.listAll()) {
                 final String zoneName = dc.getName();
                 final String zoneUuid = dc.getUuid();