Updates storage components to edition 2024. We like to stay on the
latest edition if possible. There is no functional changes, however some
code changes had to be done to accommodate the edition's breaking
changes.
The PR has two commits:
* the first commit updates storage crates to edition 2024 and appeases
`cargo clippy` by changing code. i have accidentially ran the formatter
on some files that had other edits.
* the second commit performs a `cargo fmt`
I would recommend a closer review of the first commit and a less close
review of the second one (as it just runs `cargo fmt`).
part of https://github.com/neondatabase/neon/issues/10918
## Problem
We want to do a more robust job of scheduling tenants into their home
AZ: https://github.com/neondatabase/neon/issues/8264.
Closes: https://github.com/neondatabase/neon/issues/8969
## Summary of changes
### Scope
This PR combines prioritizing AZ with a larger rework of how we do
optimisation. The rationale is that just bumping AZ in the order of
Score attributes is a very tiny change: the interesting part is lining
up all the optimisation logic to respect this properly, which means
rewriting it to use the same scores as the scheduler, rather than the
fragile hand-crafted logic that we had before. Separating these changes
out is possible, but would involve doing two rounds of test updates
instead of one.
### Scheduling optimisation
`TenantShard`'s `optimize_attachment` and `optimize_secondary` methods
now both use the scheduler to pick a new "favourite" location. Then
there is some refined logic for whether + how to migrate to it:
- To decide if a new location is sufficiently "better", we generate
scores using some projected ScheduleContexts that exclude the shard
under consideration, so that we avoid migrating from a node with
AffinityScore(2) to a node with AffinityScore(1), only to migrate back
later.
- Score types get a `for_optimization` method so that when we compare
scores, we will only do an optimisation if the scores differ by their
highest-ranking attributes, not just because one pageserver is lower in
utilization. Eventually we _will_ want a mode that does this, but doing
it here would make scheduling logic unstable and harder to test, and to
do this correctly one needs to know the size of the tenant that one is
migrating.
- When we find a new attached location that we would like to move to, we
will create a new secondary location there, even if we already had one
on some other node. This handles the case where we have a home AZ A, and
want to migrate the attachment between pageservers in that AZ while
retaining a secondary location in some other AZ as well.
- A unit test is added for
https://github.com/neondatabase/neon/issues/8969, which is implicitly
fixed by reworking optimisation to use the same scheduling scores as
scheduling.
## Problem
When picking locations for a shard, we should use a ScheduleContext that
includes all the other shards in the tenant, so that we apply proper
anti-affinity between shards. If we don't do this, then it can lead to
unstable scheduling, where we place a shard somewhere that the optimizer
will then immediately move it away from.
We didn't always do this, because it was a bit awkward to accumulate the
context for a tenant rather than just walking tenants.
This was a TODO in `handle_node_availability_transition`:
```
// TODO: populate a ScheduleContext including all shards in the same tenant_id (only matters
// for tenants without secondary locations: if they have a secondary location, then this
// schedule() call is just promoting an existing secondary)
```
This is a precursor to https://github.com/neondatabase/neon/issues/8264,
where the current imperfect scheduling during node evacuation hampers
testing.
## Summary of changes
- Add an iterator type that yields each shard along with a
schedulecontext that includes all the other shards from the same tenant
- Use the iterator to replace hand-crafted logic in optimize_all_plan
(functionally identical)
- Use the iterator in `handle_node_availability_transition` to apply
proper anti-affinity during node evacuation.
