bgp/rib-impl/src/main/java/org/opendaylight/protocol/bgp/rib/impl/ChannelOutputLimiter.java

   1 /*
   2  * Copyright (c) 2015 Cisco Systems, Inc. and others.  All rights reserved.
   3  *
   4  * This program and the accompanying materials are made available under the
   5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
   6  * and is available at http://www.eclipse.org/legal/epl-v10.html
   7  */
   8 package org.opendaylight.protocol.bgp.rib.impl;
   9
  10 import com.google.common.base.Preconditions;
  11 import io.netty.channel.ChannelFuture;
  12 import io.netty.channel.ChannelHandlerContext;
  13 import io.netty.channel.ChannelInboundHandlerAdapter;
  14 import javax.annotation.concurrent.ThreadSafe;
  15 import org.opendaylight.yangtools.yang.binding.Notification;
  16 import org.slf4j.Logger;
  17 import org.slf4j.LoggerFactory;
  18
  19 /**
  20  * A best-effort output limiter. It does not provide any fairness, and acts as a blocking gate-keeper
  21  * for a sessions' channel.
  22  */
  23 @ThreadSafe
  24 public final class ChannelOutputLimiter extends ChannelInboundHandlerAdapter {
  25     private static final Logger LOG = LoggerFactory.getLogger(ChannelOutputLimiter.class);
  26     private final BGPSessionImpl session;
  27     private volatile boolean blocked;
  28
  29     ChannelOutputLimiter(final BGPSessionImpl session) {
  30         this.session = Preconditions.checkNotNull(session);
  31     }
  32
  33     private void ensureWritable() {
  34         if (this.blocked) {
  35             LOG.trace("Blocked slow path tripped on session {}", this.session);
  36             synchronized (this) {
  37                 while (this.blocked) {
  38                     try {
  39                         LOG.debug("Waiting for session {} to become writable", this.session);
  40                         this.wait();
  41                     } catch (final InterruptedException e) {
  42                         throw new IllegalStateException("Interrupted while waiting for channel to come back", e);
  43                     }
  44                 }
  45
  46                 LOG.debug("Resuming write on session {}", this.session);
  47             }
  48         }
  49     }
  50
  51     public void write(final Notification msg) {
  52         ensureWritable();
  53         this.session.write(msg);
  54     }
  55
  56     ChannelFuture writeAndFlush(final Notification msg) {
  57         ensureWritable();
  58         return this.session.writeAndFlush(msg);
  59     }
  60
  61     public void flush() {
  62         this.session.flush();
  63     }
  64
  65     @Override
  66     public void channelWritabilityChanged(final ChannelHandlerContext ctx) throws Exception {
  67         final boolean w = ctx.channel().isWritable();
  68
  69         synchronized (this) {
  70             this.blocked = !w;
  71             LOG.debug("Writes on session {} {}", this.session, w ? "unblocked" : "blocked");
  72
  73             if (w) {
  74                 this.notifyAll();
  75             } else {
  76                 flush();
  77             }
  78         }
  79
  80         super.channelWritabilityChanged(ctx);
  81     }
  82
  83     @Override
  84     public void channelInactive(final ChannelHandlerContext ctx) throws Exception {
  85         synchronized (this) {
  86             this.blocked = false;
  87             this.notifyAll();
  88         }
  89
  90         super.channelInactive(ctx);
  91     }
  92 }