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. Then 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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