Github user zd-project commented on a diff in the pull request:
https://github.com/apache/storm/pull/2764#discussion_r209034728
--- Diff:
storm-server/src/main/java/org/apache/storm/daemon/nimbus/Nimbus.java ---
@@ -1984,11 +2074,13 @@ private int fragmentedCpu() {
Cluster cluster = new Cluster(inimbus, supervisors,
topoToSchedAssignment, topologies, conf);
cluster.setStatusMap(idToSchedStatus.get());
- long beforeSchedule = System.currentTimeMillis();
+ schedulingStartTime.set(Time.nanoTime());
scheduler.schedule(topologies, cluster);
- long scheduleTimeElapsedMs = System.currentTimeMillis() -
beforeSchedule;
- LOG.debug("Scheduling took {} ms for {} topologies",
scheduleTimeElapsedMs, topologies.getTopologies().size());
- scheduleTopologyTimeMs.update(scheduleTimeElapsedMs);
+ //Will compiler optimize the order of evalutation and cause race
condition?
--- End diff --
If compiler is allowed to hoist code, we can ended up with the case:
1) gauge "longest-scheduling-time-ms" acquires scheduling start time
2) elpased capture end time, update `schedulingDuration` Timer and
`longestSchedulingTime`
3) gauge acquires longest time from `longestSchedulingTime` and `currTime`
4) since start time isn't null, program execute statement
```java
longest = currTime - startTime > longest ? currTime - startTime : longest;
```
So it'll be slightly longer than the value of `longestSchedulingTime` for
this round. Which means we might saw jiggles in gauge value
---
