[ONOS-2592] BGP peer connection initiation on peer configuration.

Change-Id: I1892c9b9f702a4a233790a69f4289e5f4edb0ec3

+/*
+ * Copyright 2015 Open Networking Laboratory
+ *
+ * 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.onosproject.bgp.controller.impl;
+
+import java.net.InetSocketAddress;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+import java.util.concurrent.TimeUnit;
+
+import org.jboss.netty.bootstrap.ClientBootstrap;
+import org.jboss.netty.channel.ChannelFuture;
+import org.jboss.netty.channel.ChannelFutureListener;
+import org.jboss.netty.channel.ChannelPipelineFactory;
+import org.onosproject.bgp.controller.BGPCfg;
+import org.onosproject.bgp.controller.BGPController;
+import org.onosproject.bgp.controller.BGPPeerCfg;
+import org.onosproject.bgp.controller.BgpConnectPeer;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Implements connection initiation to peer on peer configuration and manage channel using netty channel handler.
+ */
+public class BgpConnectPeerImpl implements BgpConnectPeer {
+    private static final Logger log = LoggerFactory.getLogger(BgpConnectPeerImpl.class);
+
+    private ScheduledExecutorService connectExecutor = null;
+    private final String peerHost;
+    private static final int RETRY_INTERVAL = 4;
+    private final int peerPort;
+    private int connectRetryCounter = 0;
+    private int connectRetryTime;
+    private ChannelPipelineFactory pfact;
+    private ClientBootstrap peerBootstrap;
+    private BGPCfg bgpconfig;
+
+    /**
+     * Initialize timer and initiate pipeline factory.
+     *
+     * @param bgpController parent BGP controller
+     * @param remoteHost remote host to connect
+     * @param remotePort remote port to connect
+     */
+    public BgpConnectPeerImpl(BGPController bgpController, String remoteHost, int remotePort) {
+
+        this.bgpconfig = bgpController.getConfig();
+        this.pfact = new BGPPipelineFactory(bgpController, false);
+        this.peerBootstrap = Controller.peerBootstrap();
+        this.peerBootstrap.setPipelineFactory(pfact);
+        this.peerHost = remoteHost;
+        this.peerPort = remotePort;
+        this.connectRetryTime = 0;
+    }
+
+    @Override
+    public void disconnectPeer() {
+        if (connectExecutor != null) {
+            connectExecutor.shutdown();
+            connectExecutor = null;
+        }
+    }
+
+    @Override
+    public void connectPeer() {
+        scheduleConnectionRetry(this.connectRetryTime);
+    }
+
+    /**
+     * Retry connection with exponential back-off mechanism.
+     *
+     * @param retryDelay retry delay
+     */
+    private void scheduleConnectionRetry(long retryDelay) {
+        if (this.connectExecutor == null) {
+            this.connectExecutor = Executors.newSingleThreadScheduledExecutor();
+        }
+        this.connectExecutor.schedule(new ConnectionRetry(), retryDelay, TimeUnit.MINUTES);
+    }
+
+    /**
+     * Implements BGP connection and manages connection to peer with back-off mechanism in case of failure.
+     */
+    class ConnectionRetry implements Runnable {
+        @Override
+        public void run() {
+            log.debug("Connect to peer {}", peerHost);
+
+            InetSocketAddress connectToSocket = new InetSocketAddress(peerHost, peerPort);
+
+            try {
+                bgpconfig.setPeerConnState(peerHost, BGPPeerCfg.State.CONNECT);
+                peerBootstrap.connect(connectToSocket).addListener(new ChannelFutureListener() {
+                    @Override
+                    public void operationComplete(ChannelFuture future) throws Exception {
+                        if (!future.isSuccess()) {
+                            bgpconfig.setPeerConnState(peerHost, BGPPeerCfg.State.ACTIVE);
+                            connectRetryCounter++;
+                            log.error("Connection failed, ConnectRetryCounter {} remote host {}", connectRetryCounter,
+                                      peerHost);
+                            /*
+                             * Reconnect to peer on failure is exponential till 4 mins, later on retry after every 4
+                             * mins.
+                             */
+                            if (connectRetryTime < RETRY_INTERVAL) {
+                                connectRetryTime = (connectRetryTime != 0) ? connectRetryTime * 2 : 1;
+                            }
+                            scheduleConnectionRetry(connectRetryTime);
+                        } else {
+
+                            connectRetryCounter++;
+                            log.info("Connected to remote host {}, Connect Counter {}", peerHost, connectRetryCounter);
+                            disconnectPeer();
+                            return;
+                        }
+                    }
+                });
+            } catch (Exception e) {
+                log.info("Connect peer exception : " + e.toString());
+                disconnectPeer();
+            }
+        }
+    }
+}