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:
When there is no active nn in the cache, but there is active nn in the
actual environment, Let the priority of the wrong nn be the lowest of all
cache nns, so the next access can access other nn. 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), therefore I used shuffleCache. This name may be changed
to a more intuitive method name, do you have some good suggestions？
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