ctubbsii commented on code in PR #2778:
URL: https://github.com/apache/accumulo/pull/2778#discussion_r972166515
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server/base/src/main/java/org/apache/accumulo/server/conf/ServerConfigurationFactory.java:
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@@ -140,4 +158,114 @@ public void connectionEvent() {
// no-op. changes handled by prop store impl
}
}
+
+ private class ConfigRefreshRunner {
+ private static final long MIN_JITTER_DELAY = 1;
+
+ private static final long MAX_JITTER_DELAY = 23;
+ private final ScheduledFuture<?> refreshTaskFuture;
+
+ ConfigRefreshRunner() {
+
+ Runnable refreshTask = this::verifySnapshotVersions;
+ // staggering the initial delay prevents synchronization of Accumulo
servers communicating
+ // with ZooKeeper for the sync process.
+ long randDelay = jitter(REFRESH_PERIOD_MINUTES / 4,
REFRESH_PERIOD_MINUTES);
+
+ ScheduledThreadPoolExecutor executor = ThreadPools.getServerThreadPools()
+ .createScheduledExecutorService(4, "config-refresh", false);
+ refreshTaskFuture =
+ executor.scheduleWithFixedDelay(refreshTask, randDelay,
REFRESH_PERIOD_MINUTES, MINUTES);
+ }
+
+ /**
+ * Check that the stored version in ZooKeeper matches the version held in
the local snapshot.
+ * When a mismatch is detected, a change event is sent to the prop store
which will cause a
+ * re-load. If the Zookeeper node has been deleted, the local cache
entries are removed.
+ * <p>
+ * This method is designed to be called as a scheduled task, so it does
not propagate exceptions
+ * other than interrupted Exceptions so the scheduled tasks will continue
to run.
+ */
+
+ private synchronized void verifySnapshotVersions() {
Review Comment:
You can still guard with an AtomicBoolean, but without synchronizing on it.
It has its own internal synchronization. In any case, I don't think it's a
problem if there's only a single instance of this object with only a single
background thread running these checks.
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