Current version: 0.1.0
Bottlerocket has different variants supporting different features and use cases. Each variant has its own set of software, and therefore needs its own configuration. We support having an API model for each variant to support these different configurations.
Each model defines a top-level Settings structure.
It can use pre-defined structures inside, or custom ones as needed.
This Settings essentially becomes the schema for the variant's data store.
apiserver::datastore offers serialization and deserialization modules that make it easy to map between Rust types and the data store, and thus, all inputs and outputs are type-checked.
At the field level, standard Rust types can be used, or "modeled types" that add input validation.
Default values are specified in .toml files in each variant's defaults.d directory under src.
(For example, see the aws-ecs-1 defaults.)
Entries are sorted by filename, and later entries take precedence.
The #[model] attribute on Settings and its sub-structs reduces duplication and adds some required metadata; see its docs for details.
We use build.rs to symlink the proper API model source code for Cargo to build.
We determine the "proper" model by using the VARIANT environment variable.
If a developer is doing a local cargo build, they need to set VARIANT.
When building with the Bottlerocket build system, VARIANT is based on BUILDSYS_VARIANT from the top-level Makefile.toml, which can be overridden on the command line with cargo make -e BUILDSYS_VARIANT=bla.
Note: when building with the build system, we can't create the symlink in the source directory during a build - the directories are owned by root, but we're builder.
We can't use a read/write bind mount with current Docker syntax.
To get around this, in the top-level Dockerfile, we mount a "cache" directory at src/variant that we can modify, and create a current symlink inside.
The code in src/lib.rs then imports the requested model using variant/current.
Note: for the same reason, we symlink variant/mod.rs to variant_mod.rs.
Rust needs a mod.rs file to understand that a directory is part of the module structure, so we have to have variant/mod.rs.
variant/ is the cache mount that starts empty, so we have to store the file elsewhere and link it in.
Note: all models share the same Cargo.toml.
This text was generated from README.tpl using cargo-readme, and includes the rustdoc from src/lib.rs.