rebuild index command will not involve the router

I have serveral db models that require to build index in serveral cores.

Thus I defined serveral haystack connections as below:

HAYSTACK_CONNECTIONS = {
    'default': {
        'ENGINE': 'haystack.backends.solr_backend.SolrEngine',
        'URL': 'http://127.0.0.1:8983/solr/overall',
    },
    'model1': {
        'ENGINE': 'haystack.backends.solr_backend.SolrEngine',
        'URL': 'http://127.0.0.1:8983/solr/model1',
    },
    'model2': {
        'ENGINE': 'haystack.backends.solr_backend.SolrEngine',
        'URL': 'http://127.0.0.1:8983/solr/model2',
    },
}

And I create a customized router to handle the index connection.

class MulitCoresHayStackRouter(DefaultRouter):
    def for_read(self, **hints):
        return DEFAULT_ALIAS

    def for_write(self, **hints):
        alis = DEFAULT_ALIAS

        if 'instance' in hints:
            instance_class = hints['instance'].__module__ + "." + hints['instance'].__class__.__name__
            if instance_class in settings.HAYSTACK_CONNECTIONS:
                alis = instance_class
                logger.debug('Get the connection alis: %s with instance_class: %s' % (alis, instance_class))

        return alis

However, when I run the rebuild_index command, it will index all db models's data to all connections.

Is there any fixing or walkaround solution ?

Start by tracing the rebuild_index command and how it selects connections when multiple HAYSTACK_CONNECTIONS entries and a custom router are configured. Reproduce the reported behavior with the shown settings and router, then verify that rebuilding indexes each model only in its intended connection rather than every connection.