宜人贷蜂巢API网关技术解密之Netty使用实践

下面分析下Netty线程池NioEventLoopGroup的设计与实现细节，NioEventLoopGroup的类层次关系见图7：

图7 –NioEvenrLoopGroup类层次关系

其创建过程——方法调用，见下图：

图8 –NioEvenrLoopGroup创建调用关系

NioEvenrLoopGroup的创建，具体执行过程是执行类MultithreadEventExecutorGroup的构造方法：

/**  
 * Create a new instance.  
 *  
 * @param nThreads          the number of threads that will be used by this instance.  
 * @param executor          the Executor to use, or {@code null} if the default should be used.  
 * @param chooserFactory    the {@link EventExecutorChooserFactory} to use.  
 * @param args              arguments which will passed to each {@link #newChild(Executor, Object...)} call  
 */  
protected MultithreadEventExecutorGroup(int nThreads, Executor executor,  
                                        EventExecutorChooserFactory chooserFactory, Object... args) {  
    if (nThreads <= 0) {  
        throw new IllegalArgumentException(String.format("nThreads: %d (expected: > 0)", nThreads));  
    }  
    if (executor == null) {  
        executor = new ThreadPerTaskExecutor(newDefaultThreadFactory());  
    }  
    children = new EventExecutor[nThreads];  
    for (int i = 0; i < nThreads; i ++) {  
        boolean success = false;  
        try {  
            children[i] = newChild(executor, args);  
            success = true;  
        } catch (Exception e) {   
            throw new IllegalStateException("failed to create a child event loop", e);  
        } finally {  
            if (!success) {  
                for (int j = 0; j < i; j ++) {  
                    children[j].shutdownGracefully();  
                }  
                for (int j = 0; j < i; j ++) { 
                     EventExecutor e = children[j]; 
                     try { 
                         while (!e.isTerminated()) {  
                            e.awaitTermination(Integer.MAX_VALUE, TimeUnit.SECONDS);  
                        }  
                    } catch (InterruptedException interrupted) {  
                        // Let the caller handle the interruption.  
                        Thread.currentThread().interrupt();  
                        break;  
                    }  
                }  
            }  
        }  
    }  
    chooser = chooserFactory.newChooser(children);  
    final FutureListener<Object> terminationListener = new FutureListener<Object>() {  
        @Override  
        public void operationComplete(Future<Object> future) throws Exception {  
            if (terminatedChildren.incrementAndGet() == children.length) {  
                terminationFuture.setSuccess(null);  
            }  
        }  
    };  
    for (EventExecutor e: children) {  
        e.terminationFuture().addListener(terminationListener);  
    }  
    Set<EventExecutor> childrenSet = new LinkedHashSet<EventExecutor>(children.length);  
    Collections.addAll(childrenSet, children);  
    readonlyChildren = Collections.unmodifiableSet(childrenSet);  
} 

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