KeeProMise commented on code in PR #5990:
URL: https://github.com/apache/hadoop/pull/5990#discussion_r1309488817
##########
hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/resolver/MembershipNamenodeResolver.java:
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@@ -478,4 +478,40 @@ private List<MembershipState>
getRecentRegistrationForQuery(
public void setRouterId(String router) {
this.routerId = router;
}
+
+ /**
+ * Rotate cache, make the current namenode have the lowest priority,
+ * to ensure that the current namenode will not be accessed first next time.
+ *
+ * @param nsId name service id
+ * @param namenode namenode contexts
+ */
+ @Override
+ public synchronized void rotateCache(String nsId, FederationNamenodeContext
namenode) {
+ cacheNS.compute(Pair.of(nsId, false), (ns, namenodeContexts) -> {
+ if (namenodeContexts == null || namenodeContexts.size() <= 1) {
+ return namenodeContexts;
+ }
+ FederationNamenodeContext firstNamenodeContext = namenodeContexts.get(0);
+ /*
+ * 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.
+ */
+ if(firstNamenodeContext.getState().equals(ACTIVE)){
+ return namenodeContexts;
+ }
+ /*
+ * 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.getRpcAddress().equals(namenode.getRpcAddress())){
+ List<FederationNamenodeContext> rotatedNnContexts = new
ArrayList<>(namenodeContexts);
+ Collections.rotate(rotatedNnContexts, -1);
+ return rotatedNnContexts;
+ }else {
Review Comment:
done
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