No buffer space available (maximum connections reached?): connect

产生场景：
java调用es,由于代码不当，导致每次调用都会新建链接，当循环调用2万次时，报错了，发生了如下错误：

2018-07-27 11:44:28 814 | ERROR | pool-2722-thread-1 | CloseableHttpAsyncClientBase$1 | I/O reactor terminated abnormally
org.apache.http.nio.reactor.IOReactorException: Failure opening selector
    at org.apache.http.impl.nio.reactor.AbstractIOReactor.<init>(AbstractIOReactor.java:103)
    at org.apache.http.impl.nio.reactor.BaseIOReactor.<init>(BaseIOReactor.java:85)
    at org.apache.http.impl.nio.reactor.AbstractMultiworkerIOReactor.execute(AbstractMultiworkerIOReactor.java:318)
    at org.apache.http.impl.nio.conn.PoolingNHttpClientConnectionManager.execute(PoolingNHttpClientConnectionManager.java:192)
    at org.apache.http.impl.nio.client.CloseableHttpAsyncClientBase$1.run(CloseableHttpAsyncClientBase.java:64)
    at java.lang.Thread.run(Thread.java:745)
Caused by: java.io.IOException: Unable to establish loopback connection
    at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:101)
    at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:68)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.nio.ch.PipeImpl.<init>(PipeImpl.java:170)
    at sun.nio.ch.SelectorProviderImpl.openPipe(SelectorProviderImpl.java:50)
    at java.nio.channels.Pipe.open(Pipe.java:155)
    at sun.nio.ch.WindowsSelectorImpl.<init>(WindowsSelectorImpl.java:127)
    at sun.nio.ch.WindowsSelectorProvider.openSelector(WindowsSelectorProvider.java:44)
    at java.nio.channels.Selector.open(Selector.java:227)
    at org.apache.http.impl.nio.reactor.AbstractIOReactor.<init>(AbstractIOReactor.java:101)
    ... 5 more
Caused by: java.net.SocketException: No buffer space available (maximum connections reached?): connect
    at sun.nio.ch.Net.connect0(Native Method)
    at sun.nio.ch.Net.connect(Net.java:454)
    at sun.nio.ch.Net.connect(Net.java:446)
    at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:648)
    at java.nio.channels.SocketChannel.open(SocketChannel.java:189)
    at sun.nio.ch.PipeImpl$Initializer$LoopbackConnector.run(PipeImpl.java:130)
    at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:83)
    ... 14 more
2018-07-27 11:44:58 780 | INFO  | http-apr-8089-exec-2 | EntFileEsController | ========>初始化失败
java.io.IOException: listener timeout after waiting for [30000] ms
    at org.elasticsearch.client.RestClient$SyncResponseListener.get(RestClient.java:660)
    at org.elasticsearch.client.RestClient.performRequest(RestClient.java:219)
    at org.elasticsearch.client.RestClient.performRequest(RestClient.java:191)

处理办法：
不要每次查询都新建链接，建立链接这种操作，不要放在循环内部。