Upgrade Elasticsearch client to 8.0.0

Note: This is not actionable at the moment but acts as a reference of things to consider when upgrading the Elasticsearch client to 8.0.0.

Looking at the Elasticsearch client roadmap a few items stand out but specifically https://github.com/elastic/elasticsearch-py/issues/1680 will be tricky: The client will not allow to pass a body but rather requires to specify the body in a more structured manner. Initially using body will only be deprecated but we need to think about alternatives.

[pquentin]

Hmm, those options are interesting, thanks. My preference here is to merge code to master that gets used immediately, like the rally and rally-tracks PRs we merged yesterday, they were validated in our nightly benchmarks.

And yes, this means at some point we’ll have a bigger PR that makes the switch, but that’s OK. (And I’m now more familiar with the problem so reviewing will be easier.)

So basically I would suggest the following PRs:

• Switch to 7.17 and run CI with compatibility mode per https://www.elastic.co/guide/en/elasticsearch/client/python-api/current/migration.html#migration-compat-mode (this will require a few performance tests)
• Add the plumbing to pass distribution_version to the relevant classes
• (not a PR) Agree on the strategy regarding version checks (we may not get away with doing a post-flight check due to concurrency) and exception handling
• Move to 8.2 (it could be multiple commits but only one PR I think)

[pquentin]

I think it’s fine to continue using body as it will be supported in 8.0, and possibly later. If it gets removed at some point, we can always start using **body for the cases where we pass a body around before submitting to the client.