## Problem
`TYPE_CHECKING` is used inconsistently across Python tests.
## Summary of changes
- Update `ruff`: 0.7.0 -> 0.11.2
- Enable TC (flake8-type-checking):
https://docs.astral.sh/ruff/rules/#flake8-type-checking-tc
- (auto)fix all new issues
## Problem
On Debian 12 (Bookworm), Python 3.11 is the latest available version.
## Summary of changes
- Update Python to 3.11 in build-tools
- Fix ruff check / format
- Fix mypy
- Use `StrEnum` instead of pair `str`, `Enum`
- Update docs
we want to run some specific pagebench test cases on dedicated hardware
to get reproducible results
run1: 1 client per tenant => characterize throughput with n tenants.
- 500 tenants
- scale 13 (200 MB database)
- 1 hour duration
- ca 380 GB layer snapshot files
run2.singleclient: 1 client per tenant => characterize latencies
run2.manyclient: N clients per tenant => characterize throughput
scalability within one tenant.
- 1 tenant with 1 client for latencies
- 1 tenant with 64 clients because typically for a high number of
connections we recommend the connection pooler
which by default uses 64 connections (for scalability)
- scale 136 (2048 MB database)
- 20 minutes each
## Problem
see https://github.com/neondatabase/neon/issues/8070
## Summary of changes
the neon_local subcommands to
- start neon
- start pageserver
- start safekeeper
- start storage controller
get a new option -t=xx or --start-timeout=xx which allows to specify a
longer timeout in seconds we wait for the process start.
This is useful in test cases where the pageserver has to read a lot of
layer data, like in pagebench test cases.
In addition we exploit the new timeout option in the python test
infrastructure (python fixtures) and modify the flaky testcase to
increase the timeout from 10 seconds to 1 minute.
Example from the test execution
```bash
RUST_BACKTRACE=1 NEON_ENV_BUILDER_USE_OVERLAYFS_FOR_SNAPSHOTS=1 DEFAULT_PG_VERSION=15 BUILD_TYPE=release ./scripts/pytest test_runner/performance/pageserver/pagebench/test_pageserver_max_throughput_getpage_at_latest_lsn.py
...
2024-06-19 09:29:34.590 INFO [neon_fixtures.py:1513] Running command "/instance_store/neon/target/release/neon_local storage_controller start --start-timeout=60s"
2024-06-19 09:29:36.365 INFO [broker.py:34] starting storage_broker to listen incoming connections at "127.0.0.1:15001"
2024-06-19 09:29:36.365 INFO [neon_fixtures.py:1513] Running command "/instance_store/neon/target/release/neon_local pageserver start --id=1 --start-timeout=60s"
2024-06-19 09:29:36.366 INFO [neon_fixtures.py:1513] Running command "/instance_store/neon/target/release/neon_local safekeeper start 1 --start-timeout=60s"
```
## Problem
The vectored read path proposed in
https://github.com/neondatabase/neon/pull/6576 seems
to be functionally correct, but in my testing (see below) it is about 10-20% slower than the naive
sequential vectored implementation.
## Summary of changes
There's three parts to this PR:
1. Supporting vectored blob reads. This is actually trickier than it
sounds because on disk blobs are prefixed with a variable length size header.
Since the blobs are not necessarily fixed size, we need to juggle the offsets
such that the callers can retrieve the blobs from the resulting buffer.
2. Merge disk read requests issued by the vectored read path up to a
maximum size. Again, the merging is complicated by the fact that blobs
are not fixed size. We keep track of the begin and end offset of each blob
and pass them into the vectored blob reader. In turn, the reader will return
a buffer and the offsets at which the blobs begin and end.
3. A benchmark for basebackup requests against tenant with large SLRU
block counts is added. This required a small change to pagebench and a new config
variable for the pageserver which toggles the vectored get validation.
We can probably optimise things further by adding a little bit of
concurrency for our IO. In principle, it's as simple as spawning a task which deals with issuing
IO and doing the serialisation and handling on the parent task which receives input via a
channel.
