Invenio-Indexer is on PyPI so all you need is:
$ pip install invenio-indexerInvenio-Indexer depends on Invenio-Search, Invenio-Records and Celery/Kombu.
Requirements
Invenio-Indexer requires a message queue in addition to the search engine (Invenio-Search) and the database (Invenio-Records). See Kombu documentation for list of supported message queues (e.g. RabbitMQ): http://kombu.readthedocs.io/en/latest/introduction.html#transport-comparison