Enable operation in a multi-instance ONOS cluster.
Shared state has been moved to ONOS consistent maps to ensure it
is available throughout the cluster.
Event handling work (e.g. port up, etc) is partitioned between nodes
in the cluster using consistent hashing based on device ID.
Subscriber provisioning requests can be handled by any instance
(the instance that receives the request handles it).
Change-Id: I65cf24a7a7fe4397e1559e5d1c770449979f2566
diff --git a/app/src/main/java/org/opencord/olt/impl/ConsistentHasher.java b/app/src/main/java/org/opencord/olt/impl/ConsistentHasher.java
new file mode 100644
index 0000000..52e9b96
--- /dev/null
+++ b/app/src/main/java/org/opencord/olt/impl/ConsistentHasher.java
@@ -0,0 +1,130 @@
+/*
+ * Copyright 2020-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.opencord.olt.impl;
+
+import com.google.common.hash.Hashing;
+import org.onosproject.cluster.NodeId;
+
+import java.nio.charset.Charset;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Returns a server hosting a given key based on consistent hashing.
+ */
+public class ConsistentHasher {
+
+ private static class Entry implements Comparable<Entry> {
+ private final NodeId server;
+ private final int hash;
+
+ public Entry(NodeId server, int hash) {
+ this.server = server;
+ this.hash = hash;
+ }
+
+ public Entry(int hash) {
+ server = null;
+ this.hash = hash;
+ }
+
+ @Override
+ public int compareTo(Entry o) {
+ if (this.hash > o.hash) {
+ return 1;
+ } else if (this.hash < o.hash) {
+ return -1;
+ } // else
+ return 0;
+ }
+ }
+
+ private final int weight;
+
+ private List<Entry> table;
+
+ /**
+ * Creates a new hasher with the given list of servers.
+ *
+ * @param servers list of servers
+ * @param weight weight
+ */
+ public ConsistentHasher(List<NodeId> servers, int weight) {
+ this.weight = weight;
+
+ this.table = new ArrayList<>();
+
+ servers.forEach(this::addServer);
+ }
+
+ /**
+ * Adds a new server to the list of servers.
+ *
+ * @param server server ID
+ */
+ public synchronized void addServer(NodeId server) {
+ // Add weight number of buckets for each server
+ for (int i = 0; i < weight; i++) {
+ String label = server.toString() + i;
+ int hash = getHash(label);
+ Entry e = new Entry(server, hash);
+ table.add(e);
+ }
+
+ Collections.sort(table);
+ }
+
+ /**
+ * Removes a server from the list of servers.
+ *
+ * @param server server ID
+ */
+ public synchronized void removeServer(NodeId server) {
+ table.removeIf(e -> e.server.equals(server));
+ }
+
+ /**
+ * Hashes a given input string and finds that server that should
+ * handle the given ID.
+ *
+ * @param s input
+ * @return server ID
+ */
+ public synchronized NodeId hash(String s) {
+ Entry temp = new Entry(getHash(s));
+
+ int pos = Collections.binarySearch(this.table, temp);
+
+ // translate a negative not-found result into the closest following match
+ if (pos < 0) {
+ pos = Math.abs(pos + 1);
+ }
+
+ // wraparound if the hash was after the last entry in the table
+ if (pos == this.table.size()) {
+ pos = 0;
+ }
+
+ return table.get(pos).server;
+ }
+
+ private int getHash(String s) {
+ // stable, uniformly-distributed hash
+ return Hashing.murmur3_128().hashString(s, Charset.defaultCharset()).asInt();
+ }
+}