keith-turner commented on code in PR #4551:
URL: https://github.com/apache/accumulo/pull/4551#discussion_r1597500210
##########
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:
> would create a thread pool - not sure what the numbers should be.
One factor that I do not fully understand ATM is bulk updates w.r.t. to
refresh operation in Caffeine. A comment was made on #4544 stating that
caffeine refresh may be able to batch refreshes. If so, then that could work
nicely with using an Accumulo batch scanner to refresh lots of tablets metadata
in one go and would also generally mean we probably only need few threads for
refresh.
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