Reduce number of ZooCache instances and Watchers

core/src/main/java/org/apache/accumulo/core/clientImpl/ClientContext.java

@@ -79,7 +79,6 @@
 import org.apache.accumulo.core.data.TableId;
 import org.apache.accumulo.core.fate.zookeeper.ZooCache;
 import org.apache.accumulo.core.fate.zookeeper.ZooCache.ZcStat;
-import org.apache.accumulo.core.fate.zookeeper.ZooCacheFactory;
 import org.apache.accumulo.core.fate.zookeeper.ZooReader;
 import org.apache.accumulo.core.fate.zookeeper.ZooUtil;
 import org.apache.accumulo.core.lock.ServiceLock;
@@ -106,6 +105,7 @@
 import org.apache.accumulo.core.util.threads.ThreadPools;
 import org.apache.accumulo.core.util.threads.Threads;
 import org.apache.hadoop.conf.Configuration;
+import org.apache.zookeeper.KeeperException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -127,9 +127,9 @@ public class ClientContext implements AccumuloClient {
   private static final Logger log = LoggerFactory.getLogger(ClientContext.class);
 
   private final ClientInfo info;
-  private InstanceId instanceId;
+  private final Supplier<InstanceId> instanceId;
   private final ZooReader zooReader;
-  private final ZooCache zooCache;
+  private final Supplier<ZooCache> zooCache;
 
   private Credentials creds;
   private BatchWriterConfig batchWriterConfig;
@@ -229,8 +229,38 @@ public ClientContext(SingletonReservation reservation, ClientInfo info,
     this.info = info;
     this.hadoopConf = info.getHadoopConf();
     zooReader = new ZooReader(info.getZooKeepers(), info.getZooKeepersSessionTimeOut());
-    zooCache =
-        new ZooCacheFactory().getZooCache(info.getZooKeepers(), info.getZooKeepersSessionTimeOut());
+
+    // Get the instanceID using ZooKeeper, not ZooCache as we will need
+    // the instanceID to create the ZooKeeper root path when creating
+    // ZooCache. If the instanceId cannot be found, this is a good
+    // time to find out.
+    final String instanceName = info.getInstanceName();
+    final String instanceNamePath = Constants.ZROOT + Constants.ZINSTANCES + "/" + instanceName;
+
+    instanceId = memoize(() -> {
+      try {
+        // Call getZooReader() instead of using the local variable because
+        // ServerContext overrides getZooReader() to return a connection
+        // that has been set with the secret.
+        byte[] data = getZooReader().getData(instanceNamePath);
+        if (data == null) {
+          throw new IllegalArgumentException("Instance name " + instanceName
+              + " does not exist in zookeeper. "
+              + "Run \"accumulo org.apache.accumulo.server.util.ListInstances\" to see a list.");
+        }
+        final String instanceIdString = new String(data, UTF_8);
+        // verify that the instanceId found via the instanceName actually exists as an instance
+        if (getZooReader().getData(Constants.ZROOT + "/" + instanceIdString) == null) {
+          throw new IllegalArgumentException("Instance id " + instanceIdString
+              + (instanceName == null ? "" : " pointed to by the name " + instanceName)
+              + " does not exist in zookeeper");
+        }
+        return InstanceId.of(instanceIdString);
+      } catch (KeeperException | InterruptedException e) {
+        throw new IllegalArgumentException("Unable to create client, instanceId not found", e);
+      }
+    });
+    zooCache = memoize(() -> new ZooCache(ZooUtil.getRoot(getInstanceID()), getZooReader(), null));
     this.serverConf = serverConf;
     timeoutSupplier = memoizeWithExpiration(
         () -> getConfiguration().getTimeInMillis(Property.GENERAL_RPC_TIMEOUT), 100, MILLISECONDS);
@@ -484,26 +514,7 @@ public synchronized TCredentials rpcCreds() {
    * @return a UUID
    */
   public InstanceId getInstanceID() {
-    if (instanceId == null) {
-      // lookup by name
-      final String instanceName = info.getInstanceName();
-      String instanceNamePath = Constants.ZROOT + Constants.ZINSTANCES + "/" + instanceName;
-      byte[] data = zooCache.get(instanceNamePath);
-      if (data == null) {
-        throw new RuntimeException(
-            "Instance name " + instanceName + " does not exist in zookeeper. "
-                + "Run \"accumulo org.apache.accumulo.server.util.ListInstances\" to see a list.");
-      }
-      String instanceIdString = new String(data, UTF_8);
-      // verify that the instanceId found via the instanceName actually exists as an instance
-      if (zooCache.get(Constants.ZROOT + "/" + instanceIdString) == null) {
-        throw new RuntimeException("Instance id " + instanceIdString
-            + (instanceName == null ? "" : " pointed to by the name " + instanceName)
-            + " does not exist in zookeeper");
-      }
-      instanceId = InstanceId.of(instanceIdString);
-    }
-    return instanceId;
+    return instanceId.get();
   }
 
   public String getZooKeeperRoot() {
@@ -541,7 +552,7 @@ public int getZooKeepersSessionTimeOut() {
   }
 
   public ZooCache getZooCache() {
-    return zooCache;
+    return zooCache.get();
   }
 
   private TableZooHelper tableZooHelper;

core/src/main/java/org/apache/accumulo/core/clientImpl/InstanceOperationsImpl.java

@@ -19,7 +19,6 @@
 package org.apache.accumulo.core.clientImpl;
 
 import static com.google.common.base.Preconditions.checkArgument;
-import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.apache.accumulo.core.rpc.ThriftUtil.createClient;
 import static org.apache.accumulo.core.rpc.ThriftUtil.createTransport;
 import static org.apache.accumulo.core.rpc.ThriftUtil.getClient;
@@ -60,7 +59,6 @@
 import org.apache.accumulo.core.clientImpl.thrift.ThriftSecurityException;
 import org.apache.accumulo.core.conf.DeprecatedPropertyUtil;
 import org.apache.accumulo.core.data.InstanceId;
-import org.apache.accumulo.core.fate.zookeeper.ZooCache;
 import org.apache.accumulo.core.lock.ServiceLockData;
 import org.apache.accumulo.core.lock.ServiceLockData.ThriftService;
 import org.apache.accumulo.core.lock.ServiceLockPaths.AddressSelector;
@@ -467,22 +465,6 @@ public void waitForBalance() throws AccumuloException {
 
   }
 
-  /**
-   * Given a zooCache and instanceId, look up the instance name.
-   */
-  public static String lookupInstanceName(ZooCache zooCache, InstanceId instanceId) {
-    checkArgument(zooCache != null, "zooCache is null");
-    checkArgument(instanceId != null, "instanceId is null");
-    for (String name : zooCache.getChildren(Constants.ZROOT + Constants.ZINSTANCES)) {
-      var bytes = zooCache.get(Constants.ZROOT + Constants.ZINSTANCES + "/" + name);
-      InstanceId iid = InstanceId.of(new String(bytes, UTF_8));
-      if (iid.equals(instanceId)) {
-        return name;
-      }
-    }
-    return null;
-  }
-
   @Override
   public InstanceId getInstanceId() {
     return context.getInstanceID();