[GitHub] [dubbo] AlbumenJ commented on a change in pull request #8916: [Dubbo-5961] Improve consistent hashing load balancing with a new algorithm #5989

[GitBox <gi...@apache.org>]

AlbumenJ commented on a change in pull request #8916:
URL: https://github.com/apache/dubbo/pull/8916#discussion_r716620179



##########
File path: dubbo-cluster/src/main/java/org/apache/dubbo/rpc/cluster/loadbalance/ConsistentHashLoadBalance.java
##########
@@ -111,13 +149,49 @@ private String toKey(Object[] args) {
         }
 
         private Invoker<T> selectForKey(long hash) {
+            ++totalRequestCount;
             Map.Entry<Long, Invoker<T>> entry = virtualInvokers.ceilingEntry(hash);
             if (entry == null) {
                 entry = virtualInvokers.firstEntry();
             }
+            String serverAddress = entry.getValue().getUrl().getAddress();
+            double overloadThread = ((double) totalRequestCount / (double) serverCount) * overloadRatioAllowed;
+
+            /**
+             * Find a valid server node:
+             * 1. Not have accept request yet
+             * or
+             * 2. Not have overloaded (request count already accept < thread (average request count * overloadRatioAllowed ))
+             */
+            while (serverRequestCountMap.containsKey(serverAddress)
+                    && serverRequestCountMap.get(serverAddress) >= overloadThread) {
+                /**
+                 * If server node is not valid, get next node
+                 */
+                entry = virtualInvokers.higherEntry(entry.getKey());
+                if(entry == null){
+                    entry = virtualInvokers.firstEntry();
+                }
+                serverAddress = entry.getValue().getUrl().getAddress();
+            }
+
+            if (!serverRequestCountMap.containsKey(serverAddress)) {
+                //
+                serverRequestCountMap.put(serverAddress, 1L);
+            } else {
+                serverRequestCountMap.put(serverAddress, serverRequestCountMap.get(entry.getValue().getUrl().getAddress()) + 1L);

Review comment:
       Use ActomicLong.increase to prevent concurrent problem

##########
File path: dubbo-cluster/src/main/java/org/apache/dubbo/rpc/cluster/loadbalance/ConsistentHashLoadBalance.java
##########
@@ -72,6 +84,28 @@
 
         private final int[] argumentIndex;
 
+        /**
+         * key: server(invoker) address
+         * value: count of requests accept by certain server
+         */
+        private Map<String, Long> serverRequestCountMap = new HashMap<>();

Review comment:
       Change to ConcurrentHashMap to prevent concurrent problem




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