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This PR simplifies the pageserver configuration parsing as follows:
* introduce the `pageserver_api::config::ConfigToml` type
* implement `Default` for `ConfigToml`
* use serde derive to do the brain-dead leg-work of processing the toml
document
* use `serde(default)` to fill in default values
* in `pageserver` crate:
* use `toml_edit` to deserialize the pageserver.toml string into a
`ConfigToml`
* `PageServerConfig::parse_and_validate` then
* consumes the `ConfigToml`
* destructures it exhaustively into its constituent fields
* constructs the `PageServerConfig`
The rules are:
* in `ConfigToml`, use `deny_unknown_fields` everywhere
* static default values go in `pageserver_api`
* if there cannot be a static default value (e.g. which default IO
engine to use, because it depends on the runtime), make the field in
`ConfigToml` an `Option`
* if runtime-augmentation of a value is needed, do that in
`parse_and_validate`
* a good example is `virtual_file_io_engine` or `l0_flush`, both of
which need to execute code to determine the effective value in
`PageServerConf`
The benefits:
* massive amount of brain-dead repetitive code can be deleted
* "unused variable" compile-time errors when removing a config value,
due to the exhaustive destructuring in `parse_and_validate`
* compile-time errors guide you when adding a new config field
Drawbacks:
* serde derive is sometimes a bit too magical
* `deny_unknown_fields` is easy to miss
Future Work / Benefits:
* make `neon_local` use `pageserver_api` to construct `ConfigToml` and
write it to `pageserver.toml`
* This provides more type safety / coompile-time errors than the current
approach.
### Refs
Fixes #3682
### Future Work
* `remote_storage` deser doesn't reject unknown fields
https://github.com/neondatabase/neon/issues/8915
* clean up `libs/pageserver_api/src/config.rs` further
* break up into multiple files, at least for tenant config
* move `models` as appropriate / refine distinction between config and
API models / be explicit about when it's the same
* use `pub(crate)` visibility on `mod defaults` to detect stale values
40 lines
965 B
TOML
40 lines
965 B
TOML
[package]
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name = "pageserver_api"
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version = "0.1.0"
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edition.workspace = true
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license.workspace = true
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[features]
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# See pageserver/Cargo.toml
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testing = ["dep:nix"]
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[dependencies]
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serde.workspace = true
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serde_with.workspace = true
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serde_json.workspace = true
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const_format.workspace = true
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anyhow.workspace = true
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bytes.workspace = true
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byteorder.workspace = true
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utils.workspace = true
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postgres_ffi.workspace = true
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enum-map.workspace = true
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strum.workspace = true
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strum_macros.workspace = true
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hex.workspace = true
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humantime.workspace = true
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thiserror.workspace = true
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humantime-serde.workspace = true
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chrono = { workspace = true, features = ["serde"] }
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itertools.workspace = true
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storage_broker.workspace = true
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camino = {workspace = true, features = ["serde1"]}
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remote_storage.workspace = true
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postgres_backend.workspace = true
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nix = {workspace = true, optional = true}
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reqwest.workspace = true
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[dev-dependencies]
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bincode.workspace = true
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rand.workspace = true
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