ZOOKEEPER-3846: Add a couple TLS related metrics

Author: Jie Huang <jiehuang@fb.com>

Reviewers: Michael Han <hanm@apache.org>

Closes #1366 from jhuan31/ZOOKEEPER-3846

zookeeper-server/src/main/java/org/apache/zookeeper/server/NettyServerCnxnFactory.java

@@ -441,6 +441,7 @@ public class NettyServerCnxnFactory extends ServerCnxnFactory {
                 addCnxn(cnxn);
             } else {
                 LOG.error("Unsuccessful handshake with session 0x{}", Long.toHexString(cnxn.getSessionId()));
+                ServerMetrics.getMetrics().UNSUCCESSFUL_HANDSHAKE.add(1);
                 cnxn.close(ServerCnxn.DisconnectReason.FAILED_HANDSHAKE);
             }
         }

zookeeper-server/src/main/java/org/apache/zookeeper/server/ServerMetrics.java

@@ -233,6 +233,8 @@ public final class ServerMetrics {
 
         DIGEST_MISMATCHES_COUNT = metricsContext.getCounter("digest_mismatches_count");
 
+        UNSUCCESSFUL_HANDSHAKE = metricsContext.getCounter("unsuccessful_handshake");
+        INSECURE_ADMIN = metricsContext.getCounter("insecure_admin_count");
         TLS_HANDSHAKE_EXCEEDED = metricsContext.getCounter("tls_handshake_exceeded");
 
         CNXN_CLOSED_WITHOUT_ZK_SERVER_RUNNING = metricsContext.getCounter("cnxn_closed_without_zk_server_running");
@@ -462,6 +464,13 @@ public final class ServerMetrics {
     // txns to data tree.
     public final Counter DIGEST_MISMATCHES_COUNT;
 
+    public final Counter UNSUCCESSFUL_HANDSHAKE;
+
+    /*
+     * Number of insecure connections to admin port
+     */
+    public final Counter INSECURE_ADMIN;
+
     public final Counter TLS_HANDSHAKE_EXCEEDED;
 
     public final Counter CNXN_CLOSED_WITHOUT_ZK_SERVER_RUNNING;

zookeeper-server/src/main/java/org/apache/zookeeper/server/admin/UnifiedConnectionFactory.java

@@ -20,6 +20,7 @@ package org.apache.zookeeper.server.admin;
 
 import javax.net.ssl.SSLEngine;
 import javax.net.ssl.SSLSession;
+import org.apache.zookeeper.server.ServerMetrics;
 import org.eclipse.jetty.io.Connection;
 import org.eclipse.jetty.io.EndPoint;
 import org.eclipse.jetty.io.ssl.SslConnection;
@@ -94,6 +95,7 @@ public class UnifiedConnectionFactory extends AbstractConnectionFactory {
         } else {
             sslConnection = null;
             plainEndpoint = aheadEndpoint;
+            ServerMetrics.getMetrics().INSECURE_ADMIN.add(1);
         }
 
         ConnectionFactory next = connector.getConnectionFactory(nextProtocol);