- First in staging then in production.
- from v0.9 to v0.10.
for v0.10, as the schema got updated, a new index will need to be created and then a
backfill is in order to populate correctly that new index.
Rough plan to install and backfill the new index:
- Redo the tagging to v0.10.0 (it is 0.10.0 )
- stop puppet on nodes running the journal clients and swh-search
- stop the objects and metadata journal clients so they stop populating the future "old" index
- upgrade the debian packages
- restart swh-search to declare the new mappings in the old index 
- restart puppet
- manually launch journal client configured to index on a origin-v0.10 index
- reset offsets on the origin_visit_status topics for the journal clients' consumer client
- wait for the end of the reindexation (journal client: no more lags)
- upgrade the new swh-search and journal client configurations in puppet to use the new index (done for webapp1)
 That's actually not totally sure whether that's the way to do it in our case. We may
have to do this ourselves manually in another way.
 That does not agree with the packaging build