CURATOR-704. Add server compatibility check support (#497)

Add new interface ZookeeperCompatibility to represent server compatibility and the existing Compatibility class (which represents client compatibility).

Enhance CuratorFramework to accept ZookeeperCompatibility instance, allowing users to specify which server version to target (default is LATEST).

curator-client/src/main/java/org/apache/curator/utils/ZookeeperCompatibility.java

@@ -0,0 +1,71 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.apache.curator.utils;
+
+/**
+ * Describe feature supports based on server compatibility (as opposed to
+ * {@code Compatibility} which represents client compatibility.
+ */
+public class ZookeeperCompatibility {
+    /**
+     * Represent latest version with all features enabled
+     */
+    public static final ZookeeperCompatibility LATEST =
+            builder().hasPersistentWatchers(true).build();
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    public static class Builder {
+        // List of features introduced by Zookeeper over time.
+        // All values are set to false by default for backward compatibility
+        private boolean hasPersistentWatchers = false;
+
+        public Builder hasPersistentWatchers(boolean value) {
+            this.hasPersistentWatchers = value;
+            return this;
+        }
+
+        public boolean hasPersistentWatchers() {
+            return this.hasPersistentWatchers;
+        }
+
+        public ZookeeperCompatibility build() {
+            return new ZookeeperCompatibility(this);
+        }
+    }
+
+    private final boolean hasPersistentWatchers;
+
+    private ZookeeperCompatibility(Builder builder) {
+        this.hasPersistentWatchers = builder.hasPersistentWatchers;
+    }
+
+    /**
+     * Check if both client and server support persistent watchers
+     *
+     * @return {@code true} if both the client library and the server version
+     *         support persistent watchers
+     */
+    public boolean hasPersistentWatchers() {
+        return this.hasPersistentWatchers && Compatibility.hasPersistentWatchers();
+    }
+}

curator-framework/src/main/java/org/apache/curator/framework/CuratorFramework.java

@@ -34,6 +34,7 @@
 import org.apache.curator.framework.state.ConnectionStateErrorPolicy;
 import org.apache.curator.framework.state.ConnectionStateListener;
 import org.apache.curator.utils.EnsurePath;
+import org.apache.curator.utils.ZookeeperCompatibility;
 import org.apache.zookeeper.Watcher;
 import org.apache.zookeeper.server.quorum.flexible.QuorumVerifier;
 
@@ -262,6 +263,13 @@ public interface CuratorFramework extends Closeable {
      */
     public CuratorZookeeperClient getZookeeperClient();
 
+    /**
+     * Return zookeeper server compatibility
+     *
+     * @return compatibility
+     */
+    public ZookeeperCompatibility getZookeeperCompatibility();
+
     /**
      * Allocates an ensure path instance that is namespace aware
      *

curator-framework/src/main/java/org/apache/curator/framework/CuratorFrameworkFactory.java

@@ -46,6 +46,7 @@
 import org.apache.curator.framework.state.ConnectionStateListenerManagerFactory;
 import org.apache.curator.framework.state.StandardConnectionStateErrorPolicy;
 import org.apache.curator.utils.DefaultZookeeperFactory;
+import org.apache.curator.utils.ZookeeperCompatibility;
 import org.apache.curator.utils.ZookeeperFactory;
 import org.apache.zookeeper.CreateMode;
 import org.apache.zookeeper.Watcher;
@@ -174,6 +175,7 @@ public static class Builder {
                 ConnectionStateListenerManagerFactory.standard;
         private int simulatedSessionExpirationPercent = 100;
         private ZKClientConfig zkClientConfig;
+        private ZookeeperCompatibility zookeeperCompatibility = ZookeeperCompatibility.LATEST;
 
         /**
          * Apply the current values and build a new CuratorFramework
@@ -519,6 +521,11 @@ public Builder connectionStateListenerManagerFactory(
             return this;
         }
 
+        public Builder zookeeperCompatibility(ZookeeperCompatibility zookeeperCompatibility) {
+            this.zookeeperCompatibility = zookeeperCompatibility;
+            return this;
+        }
+
         public Executor getRunSafeService() {
             return runSafeService;
         }
@@ -640,6 +647,10 @@ public ConnectionStateListenerManagerFactory getConnectionStateListenerManagerFa
             return connectionStateListenerManagerFactory;
         }
 
+        public ZookeeperCompatibility getZookeeperCompatibility() {
+            return zookeeperCompatibility;
+        }
+
         private Builder() {}
     }
 

curator-framework/src/main/java/org/apache/curator/framework/imps/CuratorFrameworkImpl.java

@@ -77,11 +77,11 @@
 import org.apache.curator.framework.state.ConnectionStateErrorPolicy;
 import org.apache.curator.framework.state.ConnectionStateListener;
 import org.apache.curator.framework.state.ConnectionStateManager;
-import org.apache.curator.utils.Compatibility;
 import org.apache.curator.utils.DebugUtils;
 import org.apache.curator.utils.EnsurePath;
 import org.apache.curator.utils.ThreadUtils;
 import org.apache.curator.utils.ZKPaths;
+import org.apache.curator.utils.ZookeeperCompatibility;
 import org.apache.curator.utils.ZookeeperFactory;
 import org.apache.zookeeper.KeeperException;
 import org.apache.zookeeper.WatchedEvent;
@@ -117,6 +117,7 @@ public class CuratorFrameworkImpl implements CuratorFramework {
     private final EnsembleTracker ensembleTracker;
     private final SchemaSet schemaSet;
     private final Executor runSafeService;
+    private final ZookeeperCompatibility zookeeperCompatibility;
 
     private volatile ExecutorService executorService;
     private final AtomicBoolean logAsErrorConnectionErrors = new AtomicBoolean(false);
@@ -204,6 +205,7 @@ public void process(WatchedEvent watchedEvent) {
                 builder.withEnsembleTracker() ? new EnsembleTracker(this, builder.getEnsembleProvider()) : null;
 
         runSafeService = makeRunSafeService(builder);
+        zookeeperCompatibility = builder.getZookeeperCompatibility();
     }
 
     private Executor makeRunSafeService(CuratorFrameworkFactory.Builder builder) {
@@ -292,6 +294,7 @@ protected CuratorFrameworkImpl(CuratorFrameworkImpl parent) {
         schemaSet = parent.schemaSet;
         ensembleTracker = parent.ensembleTracker;
         runSafeService = parent.runSafeService;
+        zookeeperCompatibility = parent.zookeeperCompatibility;
     }
 
     @Override
@@ -585,8 +588,8 @@ public RemoveWatchesBuilder watches() {
     @Override
     public WatchesBuilder watchers() {
         Preconditions.checkState(
-                Compatibility.hasPersistentWatchers(),
-                "watchers() is not supported in the ZooKeeper library being used. Use watches() instead.");
+                zookeeperCompatibility.hasPersistentWatchers(),
+                "watchers() is not supported in the ZooKeeper library and/or server being used. Use watches() instead.");
         return new WatchesBuilderImpl(this);
     }
 
@@ -600,6 +603,11 @@ public CuratorZookeeperClient getZookeeperClient() {
         return client;
     }
 
+    @Override
+    public ZookeeperCompatibility getZookeeperCompatibility() {
+        return zookeeperCompatibility;
+    }
+
     @Override
     public EnsurePath newNamespaceAwareEnsurePath(String path) {
         return namespace.newNamespaceAwareEnsurePath(path);

curator-recipes/src/main/java/org/apache/curator/framework/recipes/cache/CuratorCacheBridgeBuilderImpl.java

@@ -21,7 +21,6 @@
 
 import java.util.concurrent.ExecutorService;
 import org.apache.curator.framework.CuratorFramework;
-import org.apache.curator.utils.Compatibility;
 import org.slf4j.LoggerFactory;
 
 class CuratorCacheBridgeBuilderImpl implements CuratorCacheBridgeBuilder {
@@ -57,7 +56,7 @@ public CuratorCacheBridgeBuilder withExecutorService(ExecutorService executorSer
 
     @Override
     public CuratorCacheBridge build() {
-        if (!forceTreeCache && Compatibility.hasPersistentWatchers()) {
+        if (!forceTreeCache && client.getZookeeperCompatibility().hasPersistentWatchers()) {
             if (executorService != null) {
                 LoggerFactory.getLogger(getClass()).warn("CuratorCache does not support custom ExecutorService");
             }

curator-test-zk35/src/test/java/org/apache/curator/zk35/TestIs35.java

@@ -23,6 +23,7 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import org.apache.curator.test.compatibility.CuratorTestBase;
 import org.apache.curator.utils.Compatibility;
+import org.apache.curator.utils.ZookeeperCompatibility;
 import org.junit.jupiter.api.Tag;
 import org.junit.jupiter.api.Test;
 
@@ -33,6 +34,12 @@ public void testIsZk35() {
         assertFalse(Compatibility.hasGetReachableOrOneMethod());
         assertTrue(Compatibility.hasAddrField());
         assertFalse(Compatibility.hasPersistentWatchers());
+        assertFalse(ZookeeperCompatibility.LATEST.hasPersistentWatchers());
+        assertFalse(ZookeeperCompatibility.builder().build().hasPersistentWatchers());
+        assertFalse(ZookeeperCompatibility.builder()
+                .hasPersistentWatchers(false)
+                .build()
+                .hasPersistentWatchers());
     }
 
     @Override

curator-test-zk36/src/test/java/org/apache/curator/zk36/TestIs36.java

@@ -19,10 +19,12 @@
 
 package org.apache.curator.zk36;
 
+import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 import static org.junit.jupiter.api.Assertions.fail;
 import org.apache.curator.test.compatibility.CuratorTestBase;
 import org.apache.curator.utils.Compatibility;
+import org.apache.curator.utils.ZookeeperCompatibility;
 import org.junit.jupiter.api.Tag;
 import org.junit.jupiter.api.Test;
 
@@ -33,6 +35,12 @@ public void testIsZk36() {
         assertTrue(Compatibility.hasGetReachableOrOneMethod());
         assertTrue(Compatibility.hasAddrField());
         assertTrue(Compatibility.hasPersistentWatchers());
+        assertTrue(ZookeeperCompatibility.LATEST.hasPersistentWatchers());
+        assertFalse(ZookeeperCompatibility.builder().build().hasPersistentWatchers());
+        assertFalse(ZookeeperCompatibility.builder()
+                .hasPersistentWatchers(false)
+                .build()
+                .hasPersistentWatchers());
         try {
             Class.forName("org.apache.zookeeper.proto.WhoAmIResponse");
             fail("WhoAmIResponse is introduced after ZooKeeper 3.7");

curator-x-async/src/main/java/org/apache/curator/x/async/details/AsyncCuratorFrameworkImpl.java

@@ -32,7 +32,6 @@
 import org.apache.curator.framework.imps.CuratorMultiTransactionImpl;
 import org.apache.curator.framework.imps.GetACLBuilderImpl;
 import org.apache.curator.framework.imps.SyncBuilderImpl;
-import org.apache.curator.utils.Compatibility;
 import org.apache.curator.x.async.AsyncCuratorFramework;
 import org.apache.curator.x.async.AsyncStage;
 import org.apache.curator.x.async.WatchMode;
@@ -140,8 +139,8 @@ public AsyncRemoveWatchesBuilder removeWatches() {
     @Override
     public AsyncWatchBuilder addWatch() {
         Preconditions.checkState(
-                Compatibility.hasPersistentWatchers(),
-                "addWatch() is not supported in the ZooKeeper library being used.");
+                client.getZookeeperCompatibility().hasPersistentWatchers(),
+                "addWatch() is not supported in the ZooKeeper library and/or server being used.");
         return new AsyncWatchBuilderImpl(client, filters);
     }