keith-turner commented on code in PR #4439:
URL: https://github.com/apache/accumulo/pull/4439#discussion_r1569577537
##########
server/tserver/src/main/java/org/apache/accumulo/tserver/tablet/Tablet.java:
##########
@@ -1551,40 +1569,88 @@ public enum RefreshPurpose {
MINC_COMPLETION, REFRESH_RPC, FLUSH_ID_UPDATE, LOAD
}
- public void refreshMetadata(RefreshPurpose refreshPurpose) {
+ public class RefreshSession {
+
+ private final long observedRefreshCount;
+
+ private RefreshSession(long observedRefreshCount) {
+ this.observedRefreshCount = observedRefreshCount;
+ }
+
+ /**
+ * Refresh tablet metadata using metadata that was read separately.
+ *
+ * @param tabletMetadata this tablet metadata must have been read after
calling
+ * {@link Tablet#startRefresh()}
+ */
+ public boolean refreshMetadata(RefreshPurpose refreshPurpose,
TabletMetadata tabletMetadata) {
+ return Tablet.this.refreshMetadata(refreshPurpose, observedRefreshCount,
tabletMetadata);
+ }
+ }
+
+ /**
+ * A refresh session allows code outside of this class to safely read tablet
metadata and pass it
+ * back. This is useful for the case where many tablets need to be refreshed
and we want to batch
+ * reading their metadata. Creating a refresh session will not block. A
refresh session is able to
+ * detect changes in tablet metadata that happen during its existence and
reread tablet metadata
+ * if necessary.
+ */
+ public RefreshSession startRefresh() {
+ return new RefreshSession(latestMetadata.get().refreshCount);
+ }
+
+ private boolean refreshMetadata(RefreshPurpose refreshPurpose, Long
observedRefreshCount,
+ TabletMetadata tabletMetadata) {
+
refreshLock.lock();
try {
+ var prevMetadata = latestMetadata.get();
+ // if the tablet metadata passed in is stale, then reread it
+ if (observedRefreshCount == null ||
!observedRefreshCount.equals(prevMetadata.refreshCount)) {
+ if (observedRefreshCount != null) {
+ log.debug(
+ "Metadata read outside of refresh lock is no longer valid,
rereading metadata. {} {} {}",
+ extent, observedRefreshCount, prevMetadata.refreshCount);
+ }
Review Comment:
Yeah that was the intention, but it did it in a really weird way. The code
could be more straightforward. I will update it.
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