Allow serving multiple profiles

[eimrek]

It would be useful and efficient to allow serving multiple AiiDA profiles from the same REST API. A clear use case is the Materials Cloud AiiDA rest apis.

The current (old) REST API does not allow this, and each profile needs a separate python process, which takes considerably more resources, and is more difficult to manage.

[edan-bainglass]

Can you say more @eimrek? Particularly, "each profile needs a separate python process" is regardless true for AiiDA, no? So the REST API cannot query two profiles from the same AiiDA instance at once, but it can if by profiles we mean AiiDA instances.

But maybe you say more about what you have in mind 🙏

[eimrek]

In principle one could cache the profile backends and pass them to aiida-related methods, e.g.

qb1 = orm.QueryBuilder(backend=backend1)
...query...
qb2 = orm.QueryBuilder(backend=backend2)
...query...

This is considerably faster than switching the profiles with aiida.load_profile, which would be the "intended" use case of aiida that also allows to access/query multiple profiles in a single python process.

[edan-bainglass]

Duplicate of #56