Re: [PR] HDDS-13133. Display Ratis state machine event timeline in OM web UI [ozone]

["errose28 (via GitHub)" <gi...@apache.org>]

errose28 commented on code in PR #10034:
URL: https://github.com/apache/ozone/pull/10034#discussion_r3406654507


##########
hadoop-hdds/server-scm/src/main/java/org/apache/hadoop/hdds/scm/container/placement/metrics/SCMMetrics.java:
##########
@@ -155,6 +171,22 @@ public void decrContainerStat(ContainerStat deltaStat) {
     this.containerReportWriteCount.incr(-1 * deltaStat.getWriteCount().get());
   }
 
+  public void addRatisEvent(String event) {
+    synchronized (ratisEvents) {
+      if (ratisEvents.size() >= maxRatisEvents) {
+        ratisEvents.removeFirst();
+      }
+      ratisEvents.add(Time.formatTime(Time.now()) + "|" + event);
+    }
+  }
+
+  @Metric("Ratis state machine events")
+  public String getRatisEvents() {
+    synchronized (ratisEvents) {
+      return String.join("\n", ratisEvents);

Review Comment:
   Newlines are invalid separators in Prometheus. This change prevents all SCM metrics from being ingested into Prometheus. @jojochuang we should:
   - Convert this to a different separator like `|`
   - Add a command to our acceptance tests to check that all nodes' Prometheus instances have registered metrics. 
     - Probably `GET http://localhost:9090/api/v1/targets` and ensure that `health=up` for each component.
   
   <img width="1855" height="251" alt="Image" src="https://github.com/user-attachments/assets/12439069-f0ce-4460-9328-2e7239150ccf" />



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