KeeProMise commented on code in PR #5991:
URL: https://github.com/apache/hadoop/pull/5991#discussion_r1308085693
##########
hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/resolver/MembershipNamenodeResolver.java:
##########
@@ -478,4 +478,37 @@ private List<MembershipState>
getRecentRegistrationForQuery(
public void setRouterId(String router) {
this.routerId = router;
}
+
+ /**
+ * Shuffle cache, to ensure that the current nn will not be accessed first
next time.
+ *
+ * @param nsId name service id
+ * @param namenode namenode contexts
+ */
+ @Override
+ public synchronized void shuffleCache(String nsId, FederationNamenodeContext
namenode) {
+ cacheNS.compute(Pair.of(nsId, false), (ns, namenodeContexts) -> {
+ if (namenodeContexts != null && namenodeContexts.size() > 1) {
+ FederationNamenodeContext firstNamenodeContext =
namenodeContexts.get(0);
+ /*
+ * 1.If the first nn in the cache is active, the active nn priority
cannot be lowered.
+ * This happens when other threads have already updated the cache.
+ *
+ * 2.If the first nn in the cache at this time is not the nn
+ * that needs to be lowered in priority, there is no need to rotate.
+ * This happens when other threads have already rotated the cache.
+ */
+ if (!firstNamenodeContext.getState().equals(ACTIVE)
+ &&
firstNamenodeContext.getRpcAddress().equals(namenode.getRpcAddress())) {
+ List<FederationNamenodeContext> rotatedNnContexts = new
ArrayList<>(namenodeContexts);
+ Collections.rotate(rotatedNnContexts, -1);
+ return rotatedNnContexts;
+ } else {
+ return namenodeContexts;
Review Comment:
done in pr #5990
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