KeeProMise commented on code in PR #5990:
URL: https://github.com/apache/hadoop/pull/5990#discussion_r1306272889
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hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/resolver/MembershipNamenodeResolver.java:
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@@ -478,4 +476,27 @@ 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() > 0
+ && !namenodeContexts.get(0).getState().equals(ACTIVE)
+ &&
namenodeContexts.get(0).getRpcAddress().equals(namenode.getRpcAddress())) {
+ List<FederationNamenodeContext> rotatedNnContexts = new
ArrayList<>(namenodeContexts);
+ Collections.rotate(rotatedNnContexts, -1);
Review Comment:
The purpose of this method is to reduce the priority of the next access to
the wrong nn in this request. In the default implementation of
MembershipNamenodeResolver, we can directly rotate the cache to the left,
because the cache of ns in the MembershipNamenodeResolver is a list, but
considering the implementation of other NamenodeResolver (Maybe there will be
in the future), so this name may be changed to a more intuitive method name.
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