@Override
    public void onMissing(XdsType type, String resourceName) {
        if (closed) {
            return;
        }
        if (!eventLoop.inEventLoop()) {
            eventLoop.execute(() -> onMissing(type, resourceName));
            return;
        }
        notifyWatchers("onMissing", watcher -> watcher.onMissing(type, resourceName));
    }
Removes a watcher which waits for a snapshot update.
xds/src/main/java/com/linecorp/armeria/xds/AbstractRoot.java