Netty进阶之ChannelPoolMap源码解析
作者：立小研先森
这篇文章主要介绍了Netty进阶之ChannelPoolMap源码解析,ChannelPoolMap是用来存储ChannelPool和指定key的一个集合Map,实际的应用场景就是服务器端是一个分布式集群服务,拥有多个配置地址,这样我们就可以配置多个服务地址,减轻单台服务器的压力,需要的朋友可以参考下
前言
ChannelPoolMap是用来存储ChannelPool和指定key的一个集合Map，实际的应用场景就是服务器端是一个分布式集群服务，拥有多个配置地址，这样我们就可以配置多个服务地址，减轻单台服务器的压力；Netty框架提供了ChannelPoolMap接口和AbstractChannelPoolMap抽象方法。
一、ChannelPoolMap接口源码分析
package io.netty.channel.pool;
/**
* Allows to map {@link ChannelPool} implementations to a specific key.
*
* @param <K> the type of the key
* @param <P> the type of the {@link ChannelPool}
*/
public interface ChannelPoolMap<K, P extends ChannelPool> {
/**
* Return the {@link ChannelPool} for the {@code code}. This will never return {@code null},
* but create a new {@link ChannelPool} if non exists for they requested {@code key}.
*
* Please note that {@code null} keys are not allowed.
*/
P get(K key);
/**
* Returns {@code true} if a {@link ChannelPool} exists for the given {@code key}.
*
* Please note that {@code null} keys are not allowed.
*/
boolean contains(K key);
}
接口提供了两个方法，get方法用于获取指定key对应的ChannelPool，contains方法用来判定Map集合中是否存在指定key对应的ChannelPool。
二、AbstractChannelPoolMap抽象实现类
1.get方法分析
private final ConcurrentMap<K, P> map = PlatformDependent.newConcurrentHashMap();
@Override
public final P get(K key) {
//获取ChannelPool
P pool = map.get(checkNotNull(key, "key"));
if (pool == null) {
//创建一个新的ChannelPool
pool = newPool(key);
//如果集合中存在ChannelPool,则返回老的ChannelPool对象
P old = map.putIfAbsent(key, pool);
//若果老的ChannelPool真实存在
if (old != null) {
//异步销毁新创建的ChannelPool
// We need to destroy the newly created pool as we not use it.
poolCloseAsyncIfSupported(pool);
pool = old;
}
}
return pool;
}
- 定义了一个ConcurrentMap类型的map类变量，用来存放key及其对应的ChannelPool；
- 首先会从集合中获取ChannelPool，如果不存在则创建一个新的ChannelPool；
/**
* Called once a new {@link ChannelPool} needs to be created as non exists yet for the {@code key}.
*/
protected abstract P newPool(K key);
newPool方法是一个抽象方法，需要用户自己实现ChannelPool的创建操作；
/**
* If the pool implementation supports asynchronous close, then use it to avoid a blocking close call in case
* the ChannelPoolMap operations are called from an EventLoop.
*
* @param pool the ChannelPool to be closed
*/
private static Future<Void> poolCloseAsyncIfSupported(ChannelPool pool) {
if (pool instanceof SimpleChannelPool) {
return ((SimpleChannelPool) pool).closeAsync();
} else {
try {
pool.close();
return GlobalEventExecutor.INSTANCE.newSucceededFuture(null);
} catch (Exception e) {
return GlobalEventExecutor.INSTANCE.newFailedFuture(e);
}
}
}
异步关闭ChannelPool，如果是SimpleChannelPool的实现，则调用异步方法closeAsync；如果是其它实现，则调用close方法。
2.remove方法分析
public final boolean remove(K key) {
//移除指定key的ChannelPool
P pool = map.remove(checkNotNull(key, "key"));
if (pool != null) {
//如果移除成功，则异步的关闭ChannelPool，避免阻塞方法
poolCloseAsyncIfSupported(pool);
return true;
}
return false;
}
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