@Override
    public boolean remove(PooledConnection conn) {
        if (conn == null) {
            return false;
        }
        if (!conn.isInPool()) {
            return false;
        }

        // Attempt to remove the connection from the pool.
        IConnectionPool pool = perServerPools.get(conn.getServer());
        if (pool != null) {
            return pool.remove(conn);
        } else {
            // The pool for this server no longer exists (maybe due to it failling out of
            // discovery).
            conn.setInPool(false);
            metrics.connsInPool().decrementAndGet();
            return false;
        }
    }
Gracefully shuts down a DefaultClientChannelManager by allowing in-flight requests to finish before closing the connections.
Idle connections in the connection pools are closed, and any connections associated with an in-flight request
will be closed upon trying to return the connection to the pool
zuul-core/src/main/java/com/netflix/zuul/netty/connectionpool/DefaultClientChannelManager.java