@Override
    public void addIfAsSourceDispatcher(Class aClass) throws IllegalAccessException, InstantiationException {
        if (!aClass.isInterface() && !Modifier.isAbstract(
            aClass.getModifiers()) && SourceDispatcher.class.isAssignableFrom(aClass)) {
            Type[] genericInterfaces = aClass.getGenericInterfaces();
            for (Type genericInterface : genericInterfaces) {
                ParameterizedType anInterface = (ParameterizedType) genericInterface;
                if (anInterface.getRawType().getTypeName().equals(SourceDispatcher.class.getName())) {
                    Type[] arguments = anInterface.getActualTypeArguments();

                    if (arguments.length != 1) {
                        throw new UnexpectedException("unexpected type argument number, class " + aClass.getName());
                    }
                    Type argument = arguments[0];

                    Object source = ((Class) argument).newInstance();

                    if (!ISource.class.isAssignableFrom(source.getClass())) {
                        throw new UnexpectedException(
                            "unexpected type argument of class " + aClass.getName() + ", should be `org.apache.skywalking.oap.server.core.source.Source`. ");
                    }

                    ISource dispatcherSource = (ISource) source;
                    SourceDispatcher dispatcher = (SourceDispatcher) aClass.newInstance();

                    int scopeId = dispatcherSource.scope();

                    List<SourceDispatcher<ISource>> dispatchers = this.dispatcherMap.get(scopeId);
                    if (dispatchers == null) {
                        dispatchers = new ArrayList<>();
                        this.dispatcherMap.put(scopeId, dispatchers);
                    }

                    dispatchers.add(dispatcher);

                    LOGGER.info("Dispatcher {} is added into DefaultScopeDefine {}.", dispatcher.getClass()
                                                                                                .getName(), scopeId);
                }
            }
        }
    }
Dispatcher is only generated by oal script analysis result.
So these will/could be possible, the given source doesn't have the dispatcher,
when the receiver is open, and oal script doesn't ask for analysis.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/analysis/DispatcherManager.java