public static boolean registerConnectionManager(HttpClientConnectionManager connectionManager, long maxIdleInMs) {
        if (instance == null) {
            synchronized (IdleConnectionReaper.class) {
                if (instance == null) {
                    instance = new IdleConnectionReaper();
                    instance.start();
                }
            }
        }
        return connectionManagers.put(connectionManager, maxIdleInMs) == null;
    }
Registers the given connection manager with this reaper;

@param connectionManager Connection manager to register
@param maxIdleInMs       Max idle connection timeout in milliseconds for this connection manager.
@return true if the connection manager has been successfully registered; false otherwise.
aws-java-sdk-core/src/main/java/com/amazonaws/http/IdleConnectionReaper.java