java - Apache PoolingHttpClientConnectionManager throwing illegal state exception

Question

Here is how I use it -

private static final PoolingHttpClientConnectionManager connPool;

static {

        connPool = new PoolingHttpClientConnectionManager();
        // Increase max total connection to 200
        connPool.setMaxTotal(200);//configurable through app.properties
        // Increase default max connection per route to 50
        connPool.setDefaultMaxPerRoute(20);//configurable through app.properties

}

CloseableHttpClient httpClient = HttpClients.custom()
                .setConnectionManager(connPool) .build();

ALso I have put a finally block around http GET -

finally {
            try {
                httpClient.close();
            } catch (IOException e) {
                LOGGER.error(e.getMessage());   
            }
        }

Here is my stacktrace -

java.lang.IllegalStateException: Connection pool shut down
    at org.apache.http.util.Asserts.check(Asserts.java:34)
    at org.apache.http.pool.AbstractConnPool.lease(AbstractConnPool.java:169)
    at org.apache.http.impl.conn.PoolingHttpClientConnectionManager.requestConnection(PoolingHttpClientConnectionManager.java:217)
    at org.apache.http.impl.execchain.MainClientExec.execute(MainClientExec.java:157)
    at org.apache.http.impl.execchain.ProtocolExec.execute(ProtocolExec.java:194)
    at org.apache.http.impl.execchain.RetryExec.execute(RetryExec.java:85)
    at org.apache.http.impl.execchain.RedirectExec.execute(RedirectExec.java:108)
    at org.apache.http.impl.client.InternalHttpClient.doExecute(InternalHttpClient.java:186)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:82)
    at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:106)
    at com.A.B.C.CustomHttpClient.doGETAndValidate(CustomHttpClient.java:44)
    at com.A.B.C.SiteMonitorTask.monitorAndUpdateEndPoints(SiteMonitorTask.java:48)
    at com.A.B.C.SiteMonitorTask.run(SiteMonitorTask.java:37)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at java.lang.Thread.run(Thread.java:744)

I am using Quartz to schedule a job of monitoring Http end points.. Here is my connection pool configuration

totalMaxHttpConn=200
maxHttpConnPerRoute=20

Maven dependency.. artifact version

httpclient 4.3.1
httpcore 4.3.1

EDIT - Well the problem got away by not closing CloseableHttpClient in the finally block.. Can anyone tell why is it behaving like that? Why is connection pool shut down if i close a client?

Is the closeablehttpclient above is a handle to the pool rather than a single conn

Answer 1

In version 4.4 the method setConnectionManagerShared(boolean) was added to HttpClientBuilder.

If you set it to true the client won't close the connection manager.

HttpClients.custom()
            .setConnectionManager(Util.getConnectionManager()) // shared connection manager
            .setConnectionManagerShared(true)