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🧑 Users ​

The Users module is Xila's in-memory identity and group membership registry.

Role in system ​

  • Supplies user/group identity data for permission checks and ownership metadata.
  • Allocates and resolves typed identifiers used by task and VFS layers.
  • Guarantees root account/group bootstrap at manager initialization.

Responsibilities and boundaries ​

In scope

  • User/group insertion and lookup.
  • Membership tracking (add_to_group, is_in_group, get_user_groups).
  • Identifier and name resolution APIs.

Out of scope

  • Credential verification policy (current check_credentials is placeholder-like).
  • Authentication/session/token management.
  • Persistent storage (state is runtime memory only).

Internal architecture ​

  • Singleton manager via initialize() and get_instance().
  • Internal RwLock protects:
    • users: BTreeMap<UserIdentifier, InternalUser>,
    • groups: BTreeMap<GroupIdentifier, InternalGroup>.
  • InternalUser stores name + primary group.
  • InternalGroup stores group name + membership set (BTreeSet<UserIdentifier>).

Contract vs implementation

  • Contract: typed identifier APIs and membership/name lookup behavior.
  • Implementation: exact map/set layout, root bootstrap details, allocation scan strategy.

Lifecycle and execution model ​

  1. Initialize manager once; root user/group are inserted immediately.
  2. Allocate identifiers for additional users/groups.
  3. Register users/groups and membership before launching constrained workloads.
  4. Query identity/membership during runtime from task/VFS policy paths.

Data/control flow ​

  • Task metadata uses user/group identifiers from this module.
  • VFS permission checks call users::is_in_group(...) during access control.
  • Name-based resolution provides bridge between human-readable config and typed runtime ids.

Concurrency and synchronization model ​

  • Single RwLock guards all user/group data.
  • Read operations scale concurrently.
  • Mutating operations (add user/group/member) take write lock and enforce duplicate checks.

Dependency model ​

  • Used directly by Task and Virtual file system.
  • Higher-level authentication crate composes over this module rather than embedding inside it.

Failure semantics and recovery behavior ​

  • Duplicate identifiers/names return explicit duplicate errors.
  • Invalid user/group references return typed invalid-identifier errors.
  • Identifier allocation fails with TooManyUsers / TooManyGroups on range exhaustion.

Extension points ​

  • Add richer metadata per user/group while preserving typed id model.
  • Add batch APIs for provisioning workflows.
  • Add persistent snapshot/load layers in higher-level components.

Known limitations and trade-offs ​

  • Runtime-only storage; no built-in persistence.
  • Current credential-check method is not a complete authentication implementation.
  • Simplicity of global manager trades off horizontal sharding/partitioning.

References / See also ​