[ 
https://issues.apache.org/jira/browse/GEODE-8623?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17233734#comment-17233734
 ] 

ASF GitHub Bot commented on GEODE-8623:
---------------------------------------

jinmeiliao commented on a change in pull request #5743:
URL: https://github.com/apache/geode/pull/5743#discussion_r525312958



##########
File path: geode-common/src/main/java/org/apache/geode/internal/Retry.java
##########
@@ -47,45 +47,44 @@ public void sleep(long sleepTime, TimeUnit sleepTimeUnit) 
throws InterruptedExce
     }
   }
 
-  private static final SteadyClock steadyClock = new SteadyClock();
+  private static final SteadyTimer steadyClock = new SteadyTimer();
 
   /**
    * Try the supplier function until the predicate is true or timeout occurs.
    *
    * @param timeout to retry for
+   * @param timeoutUnit the unit for timeout
    * @param interval time between each try
-   * @param timeUnit to retry for
+   * @param intervalUnit the unit for interval
    * @param supplier to execute until predicate is true or times out
    * @param predicate to test for retry
    * @param <T> type of return value
    * @return value from supplier after it passes predicate or times out.
    */
-  public static <T> T tryFor(long timeout,
-      long interval,
-      TimeUnit timeUnit,
+  public static <T> T tryFor(long timeout, TimeUnit timeoutUnit,
+      long interval, TimeUnit intervalUnit,
       Supplier<T> supplier,
       Predicate<T> predicate) throws TimeoutException, InterruptedException {
-    return tryFor(timeout, interval, timeUnit, supplier, predicate, 
steadyClock);
+    return tryFor(timeout, timeoutUnit, interval, intervalUnit, supplier, 
predicate, steadyClock);
   }
 
   @VisibleForTesting
-  static <T> T tryFor(long timeout,
-      long interval,
-      TimeUnit timeUnit,
+  static <T> T tryFor(long timeout, TimeUnit timeoutUnit,
+      long interval, TimeUnit intervalUnit,
       Supplier<T> supplier,
       Predicate<T> predicate,
-      Clock clock) throws TimeoutException, InterruptedException {
-    long until = clock.nanoTime() + NANOSECONDS.convert(timeout, timeUnit);
+      Timer timer) throws TimeoutException, InterruptedException {
+    long until = timer.nanoTime() + NANOSECONDS.convert(timeout, timeoutUnit);
 
     T value;
     do {
       value = supplier.get();
       if (predicate.test(value)) {
         return value;
       } else {
-        clock.sleep(interval, timeUnit);
+        timer.sleep(interval, intervalUnit);

Review comment:
       @Bill Your example is a special case where the LAST iteration is the 
ONLY iteration. The extra computing only makes a difference in the LAST 
iteration and only when it throws a TimeoutException.
   
   I will try to make my case one more time, if after this, you guys still 
insist, I will rest my case.
   
   1. Without the extra calculation, we would NEVER delay a normal return, we 
will only delay a TimeoutException by a little bit (maximum the rest period). 
Since we are going to timeout anyway, I don't really care about this little 
extra wait time.
   2. The extra calculation only make a difference in the last iteration when 
it's about to reach a timeout, for all the previous loops, it's a waste of time 
and an extra call to the timer.getTime().
   3. `until - now` could be negative, so instead of the one liner 
`timer.sleep(interval, intervalUnit)`, we need to make extra calculation and 
and if/else block, which completely take the beauty, simplicity and readability 
out of the code. Personally I think the detriment overweights the benefit. 
   
   But if you guys still think otherwise, do let me know. I will make the 
change. @Bill @pivotal-jbarrett 




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> Timing between DNS and Geode startup can result in permanent unknown host 
> exceptions.
> -------------------------------------------------------------------------------------
>
>                 Key: GEODE-8623
>                 URL: https://issues.apache.org/jira/browse/GEODE-8623
>             Project: Geode
>          Issue Type: Bug
>    Affects Versions: 1.9.0, 1.9.1, 1.10.0, 1.9.2, 1.11.0, 1.12.0, 1.13.0, 
> 1.14.0, 1.13.1
>            Reporter: Jacob Barrett
>            Priority: Minor
>              Labels: pull-request-available
>
> In a managed environment were local host name DNS entries and the startup of 
> Geode happen concurrently it is possible for Geode to fail name resolution in 
> the local hostname caching. If it fails to resolve the local hostname when 
> loading the caching utility class then any service dependent on this name 
> will fail without chance for recovery.
> {code}
> [error 2020/09/30 19:50:21.644 UTC <main> tid=0x1] Jmx manager could not be 
> started because java.net.UnknownHostException
> org.apache.geode.management.ManagementException: java.net.UnknownHostException
>       at 
> org.apache.geode.management.internal.ManagementAgent.startAgent(ManagementAgent.java:133)
>       at 
> org.apache.geode.management.internal.SystemManagementService.startManager(SystemManagementService.java:432)
>       at 
> org.apache.geode.management.internal.beans.ManagementAdapter.handleCacheCreation(ManagementAdapter.java:181)
>       at 
> org.apache.geode.management.internal.beans.ManagementListener.handleEvent(ManagementListener.java:127)
>       at 
> org.apache.geode.distributed.internal.InternalDistributedSystem.notifyResourceEventListeners(InternalDistributedSystem.java:2063)
>       at 
> org.apache.geode.distributed.internal.InternalDistributedSystem.handleResourceEvent(InternalDistributedSystem.java:606)
>       at 
> org.apache.geode.internal.cache.GemFireCacheImpl.initialize(GemFireCacheImpl.java:1239)
>       at 
> org.apache.geode.internal.cache.InternalCacheBuilder.create(InternalCacheBuilder.java:219)
>       at 
> org.apache.geode.internal.cache.InternalCacheBuilder.create(InternalCacheBuilder.java:171)
>       at org.apache.geode.cache.CacheFactory.create(CacheFactory.java:142)
>       at 
> org.apache.geode.distributed.internal.DefaultServerLauncherCacheProvider.createCache(DefaultServerLauncherCacheProvider.java:52)
>       at 
> org.apache.geode.distributed.ServerLauncher.createCache(ServerLauncher.java:887)
>       at 
> org.apache.geode.distributed.ServerLauncher.start(ServerLauncher.java:803)
>       at 
> org.apache.geode.distributed.ServerLauncher.run(ServerLauncher.java:732)
>       at 
> org.apache.geode.distributed.ServerLauncher.main(ServerLauncher.java:251)
> Caused by: java.net.UnknownHostException
>       at 
> org.apache.geode.internal.net.SocketCreator.getLocalHost(SocketCreator.java:285)
>       at 
> org.apache.geode.management.internal.ManagementAgent.configureAndStart(ManagementAgent.java:310)
>       at 
> org.apache.geode.management.internal.ManagementAgent.startAgent(ManagementAgent.java:131)
>       ... 14 more
> [error 2020/09/30 19:50:21.724 UTC <main> tid=0x1] 
> org.apache.geode.management.ManagementException: java.net.UnknownHostException
> Exception in thread "main" org.apache.geode.management.ManagementException: 
> java.net.UnknownHostException
>       at 
> org.apache.geode.management.internal.ManagementAgent.startAgent(ManagementAgent.java:133)
>       at 
> org.apache.geode.management.internal.SystemManagementService.startManager(SystemManagementService.java:432)
>       at 
> org.apache.geode.management.internal.beans.ManagementAdapter.handleCacheCreation(ManagementAdapter.java:181)
>       at 
> org.apache.geode.management.internal.beans.ManagementListener.handleEvent(ManagementListener.java:127)
>       at 
> org.apache.geode.distributed.internal.InternalDistributedSystem.notifyResourceEventListeners(InternalDistributedSystem.java:2063)
>       at 
> org.apache.geode.distributed.internal.InternalDistributedSystem.handleResourceEvent(InternalDistributedSystem.java:606)
>       at 
> org.apache.geode.internal.cache.GemFireCacheImpl.initialize(GemFireCacheImpl.java:1239)
>       at 
> org.apache.geode.internal.cache.InternalCacheBuilder.create(InternalCacheBuilder.java:219)
>       at 
> org.apache.geode.internal.cache.InternalCacheBuilder.create(InternalCacheBuilder.java:171)
>       at org.apache.geode.cache.CacheFactory.create(CacheFactory.java:142)
>       at 
> org.apache.geode.distributed.internal.DefaultServerLauncherCacheProvider.createCache(DefaultServerLauncherCacheProvider.java:52)
>       at 
> org.apache.geode.distributed.ServerLauncher.createCache(ServerLauncher.java:887)
>       at 
> org.apache.geode.distributed.ServerLauncher.start(ServerLauncher.java:803)
>       at 
> org.apache.geode.distributed.ServerLauncher.run(ServerLauncher.java:732)
>       at 
> org.apache.geode.distributed.ServerLauncher.main(ServerLauncher.java:251)
> Caused by: java.net.UnknownHostException
>       at 
> org.apache.geode.internal.net.SocketCreator.getLocalHost(SocketCreator.java:285)
>       at 
> org.apache.geode.management.internal.ManagementAgent.configureAndStart(ManagementAgent.java:310)
>       at 
> org.apache.geode.management.internal.ManagementAgent.startAgent(ManagementAgent.java:131)
>       ... 14 more
> {code}



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