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## Problem L0 compaction frequently gets starved out by other background tasks and image/GC compaction. L0 compaction must be responsive to keep read amplification under control. Touches #10694. Resolves #10689. ## Summary of changes Use a separate semaphore for the L0-only compaction pass. * Add a `CONCURRENT_L0_COMPACTION_TASKS` semaphore and `BackgroundLoopKind::L0Compaction`. * Add a setting `compaction_l0_semaphore` (default off via `compaction_l0_first`). * Use the L0 semaphore when doing an `OnlyL0Compaction` pass. * Use the background semaphore when doing a regular compaction pass (which includes an initial L0 pass). * While waiting for the background semaphore, yield for L0 compaction if triggered. * Add `CompactFlags::NoYield` to disable L0 yielding, and set it for the HTTP API route. * Remove the old `use_compaction_semaphore` setting and compaction-scoped semaphore. * Remove the warning when waiting for a semaphore; it's noisy and we have metrics.
Local Development Control Plane (neon_local)
This crate contains tools to start a Neon development environment locally. This utility can be used with the cargo neon command. This is a convenience to invoke
the neon_local binary.
Note: this is a dev/test tool -- a minimal control plane suitable for testing code changes locally, but not suitable for running production systems.
Example: Start with Postgres 16
To create and start a local development environment with Postgres 16, you will need to provide --pg-version flag to 3 of the start-up commands.
cargo neon init --pg-version 16
cargo neon start
cargo neon tenant create --set-default --pg-version 16
cargo neon endpoint create main --pg-version 16
cargo neon endpoint start main
Example: Create Test User and Database
By default, cargo neon starts an endpoint with cloud_admin and postgres database. If you want to have a role and a database similar to what we have on the cloud service, you can do it with the following commands when starting an endpoint.
cargo neon endpoint create main --pg-version 16 --update-catalog true
cargo neon endpoint start main --create-test-user true
The first command creates neon_superuser and necessary roles. The second command creates test user and neondb database. You will see a connection string that connects you to the test user after running the second command.