ben-manes commented on code in PR #4551:
URL: https://github.com/apache/accumulo/pull/4551#discussion_r1597510045
##########
server/tserver/src/main/java/org/apache/accumulo/tserver/ScanServer.java:
##########
@@ -246,9 +246,30 @@ public ScanServer(ScanServerOpts opts, String[] args) {
LOG.warn(
"Tablet metadata caching less than one minute, may cause excessive
scans on metadata table.");
}
- tabletMetadataCache =
- Caffeine.newBuilder().expireAfterWrite(cacheExpiration,
TimeUnit.MILLISECONDS)
-
.scheduler(Scheduler.systemScheduler()).recordStats().build(tabletMetadataLoader);
+
+ // Get the cache refresh percentage property
+ // Value must be less than 100% as 100 or over would effectively disable
it
+ double cacheRefreshPercentage =
+
getConfiguration().getFraction(Property.SSERV_CACHED_TABLET_METADATA_REFRESH_PERCENT);
+ Preconditions.checkArgument(cacheRefreshPercentage < cacheExpiration,
+ "Tablet metadata cache refresh percentage is '%s' but must be less
than 1",
+ cacheRefreshPercentage);
+
+ var builder = Caffeine.newBuilder().expireAfterWrite(cacheExpiration,
TimeUnit.MILLISECONDS)
Review Comment:
yes, that would work, though you don't need a dedicated thread to poll. If
you lock within the asyncReload method then you can detect if the request is
the start of a new batch and schedule a task to run at the end of the time
window. That task would lock, accumulate the work, unlock, submit it for
processing, and complete the pending futures. The lock hold times are a few
nanoseconds to coordinate and you can defer to a processing thread pool to
allow for parallel batches if helpful (e.g. if a batch size limit).
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