[fti] add cw_fti_index_rql_limit method
Improves on and deprecate cw_fti_index_rql_queries: execute the rql
directly, so that we don't need to compute the set of eids up-front, but
can just keep track of the last seen entity. Use the new method in
reindex_entities.
Keep calling cw_fti_index_rql_queries if it has been redefined (e.g in
cubes).
Related to #3621392.
.. -*- coding: utf-8 -*-
Migrating cubicweb instances - benefits from a distributed architecture
=======================================================================
Migrate apache & cubicweb
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**Aim** : do the migration for N cubicweb instances hosted on a server to another with no downtime.
**Prerequisites** : have an explicit definition of the database host (not default or localhost). In our case, the database is hosted on another host.
**Steps** :
1. *on new machine* : install your environment (*pseudocode*) ::
apt-get install cubicweb cubicweb-applications apache2
2. *on old machine* : copy your cubicweb and apache configuration to the new machine ::
scp /etc/cubicweb.d/ newmachine:/etc/cubicweb.d/
scp /etc/apache2/sites-available/ newmachine:/etc/apache2/sites-available/
3. *on new machine* : start your instances ::
cubicweb start
4. *on new machine* : enable sites and modules for apache and start it, test it using by modifying your /etc/host file.
5. change dns entry from your oldmachine to newmachine
6. shutdown your *old machine* (if it doesn't host other services or your database)
7. That's it.
**Possible enhancements** : use right from the start a pound server behind your apache, that way you can add backends and smoothily migrate by shuting down backends that pound will take into account.