@Override
        public ConnectionPool call() throws Exception {
            final ConnectionPool pool = new ConnectionPool(connectionSelectStrategy);
            if (whetherInitConnection) {
                try {
                    doCreate(this.url, pool, this.getClass().getSimpleName(),
                        syncCreateNumWhenNotWarmup);
                } catch (Exception e) {
                    pool.removeAllAndTryClose();
                    connTasks.remove(url.getUniqueKey());
                    throw e;
                }
            }
            return pool;
        }
create a {@link ConnectionPool} and init connections with the specified {@link Url}

@param url target url
src/main/java/com/alipay/remoting/DefaultConnectionManager.java