@Override
    public void notifyTargetInvalid(Target target) {
        log.log(Level.FINE, () -> "Target invalid " + target);
        for (Iterator<DelayedResponse> it = proxyServer.delayedResponses().responses().iterator(); it.hasNext(); ) {
            DelayedResponse delayed = it.next();
            JRTServerConfigRequest request = delayed.getRequest();
            if (request.getRequest().target().equals(target)) {
                log.log(Level.FINE, () -> "Removing " + request.getShortDescription());
                it.remove();
            }
        }
        // TODO: Could we also cancel active getConfig requests upstream if the client was the only one
        // requesting this config?
    }
Removes invalid targets (closed client connections) from delayedResponsesQueue.

@param target a Target that has become invalid (i.e, client has closed connection)
config-proxy/src/main/java/com/yahoo/vespa/config/proxy/ConfigProxyRpcServer.java