Jakob Degen

This commit introduces a **new capability** for immediate, unbuffered event delivery within the **`buck2_events`** system, primarily to **fix** a critical issue where resource control events were lost before OOMs. It adds a `send_now` method to the `EventSink` trait and implements it across various sinks, including `Scribe`, ensuring events bypass internal queues. The **`buck2_resource_control`** module is updated to utilize this new `instant_event_send_now` function, specifically in `spawn_memory_reporter`, to guarantee the delivery of memory-related events. This change significantly improves the reliability of critical resource control event reporting, enhancing observability and debugging capabilities, especially under high memory pressure.

This commit **refactors** the **`buck2 targets` command** by **flipping the default value** of the `target-hash-recursive` argument from `true` to `false`. This change is a **preparatory step for deprecating and removing** recursive target hashing, which telemetry indicates is largely unused. Consequently, the default behavior of `buck2 targets` will now be non-recursive hashing unless explicitly specified. **Help output** and various **test suites** are updated to reflect this new default, with tests explicitly setting `target-hash-recursive=true` to maintain their original recursive hashing behavior and prevent regressions.

This commit **configures the Clippy linting rules** by **disabling the `needless_continue` lint** across the project. It specifically adds `clippy::needless_continue` to the list of allowed lints within the `lint_levels.bzl` configuration file. This **maintenance change** adjusts the **code quality enforcement** to permit the use of `continue` statements even when Clippy might otherwise deem them redundant. The decision was made to avoid negatively impacting the clarity or correctness of specific code sections, as noted in a related change (D96755024).

This commit introduces a **fix** and **refactoring** to the **cgroups resource control** subsystem, specifically addressing the **experimental suspension algorithm variant**. It **guards** the initialization and computation of this experimental variant behind the `enable_suspension` flag within `app/buck2_resource_control/src/scheduler.rs`, preventing potential issues arising from version mismatches or unintended activation. Additionally, the configuration key `suspension_experimental_algo_variant` in `app/buck2_common/src/init.rs` has been **renamed** to `experimental_suspension_algo_variant` to align with this controlled rollout and avoid conflicts with previously released versions. This ensures that the experimental behavior is only enabled when explicitly configured, improving the stability and predictability of **resource management**.

This commit **reverts** the functionality that integrated anonymous target nodes into the critical path calculation and split analysis, addressing a **memory regression**. The logic for splitting analysis based on anonymous target resolution, associated timing data, and critical path integration has been removed from the **buck2_analysis**, **buck2_anon_target**, and **buck2_build_signals_impl** modules. This rollback also removes related display logic from `buck2_event_observer` and adapts `buck2_build_api` and `buck2_bxl` to the updated analysis APIs. The change effectively removes the experimental split analysis and critical path tracking for anonymous targets, restoring previous memory performance.

This commit introduces a **new capability** to the **resource control event reporting** system by adding a `tags` field to the `ResourceControlEvent` protobuf message. It modifies the `Scheduler` within the `buck2_resource_control` module to generate and attach these tags, specifically indicating whether suspension is enabled, to outgoing events. This enhancement allows for more granular categorization and analysis of resource control activities, improving observability and debugging capabilities. The `EventSenderState` and event sending logic are updated to manage and include these new tags.

This commit introduces a **new capability** within the **`buck2_resource_control`** module to enhance diagnostics for memory pressure. It modifies `app/buck2_resource_control/src/scheduler.rs` to add a `base_tags` field to the `Scheduler` and implements logic to attach an `expected_oom_kill` tag to events when memory pressure exceeds a predefined threshold. This **feature addition** provides **improved observability** by logging an early indication when a process is likely to be terminated by the OOM killer, aiding in debugging resource-related issues.

This commit introduces **experimental variants** of the **kill timing algorithm** and **future pressure prediction** within the `buck2_resource_control` subsystem. These new algorithms are integrated into the `calculate_kill_interval` method in `scheduler.rs`, allowing for evaluation of different strategies for managing resource pressure. This **new feature development** aims to optimize resource allocation and process termination, with the `RESOURCE_CONTROL_ALGO_VERSION` in `init.rs` being incremented to reflect these significant changes. The work sets the stage for an experiment to determine the most effective resource control strategy, directly impacting how processes are managed under resource constraints.

This commit establishes **infrastructure** within the **resource control scheduler** to support experimental algorithm variants. It introduces a new configuration option, `suspension_experimental_algo_variant`, in `ResourceControlConfig` via `app/buck2_common/src/init.rs`. This allows the `buck2_resource_control` module's `Scheduler` to integrate and concurrently test different scheduling algorithm variations, facilitating future performance improvements and optimizations in resource management.

This commit **reverts** a previous change (D95834528) that had exposed certain **Starlark typing internals** as public API. It specifically **restricts the visibility** of the `validate_fn_call` function within the `starlark-rust/starlark/src/typing/oracle/ctx.rs` module and the `StarlarkValueAsTypeStarlarkValue` struct in `starlark-rust/starlark/src/values/types/starlark_value_as_type.rs`. These components are now reverted to **crate-private** or **private** visibility, respectively. This **revert** ensures that these internal implementation details are no longer part of the **public API** of the `starlark-rust` library, preventing unintended external dependencies and maintaining a more controlled API surface.

This commit **reverts** the implementation of **`Select[T]` type parameterization** within the **Starlark type system**, effectively undoing the changes introduced by the original commit D94266514. It rolls back modifications across the `starlark-rust` crate, specifically removing the `parametrize` function and related type expression resolution logic in `starlark/src/typing/`, and reverting the addition of `fn_list` in `starlark/src/eval/compiler/constants.rs`. This **revert** also updates relevant tests in `app/buck2_interpreter_for_build_tests/` and `tests/select_type_params/` to reflect the removal of this **new capability**, adjusting assertions and adding `TODO` comments. The overall impact is to remove the generic type support for `Select` expressions and associated **refactorings** from the Starlark interpreter.

This commit **refactors** the internal representation of the `default_target_platform` attribute within Buck2, changing it from a generic `label` to a dedicated **`configuration_dep` type**. This **enhancement** primarily impacts the **configuration system** and **query tools**, ensuring that `default_target_platform` is correctly identified and listed as a configuration dependency. Specifically, it enables `uquery` to accurately report `default_target_platform` in its `configuration_deps` output, improving the introspection and analysis of build configurations. The change also includes adjustments to dependency checking logic in `check_within_view` and updates to various tests to reflect the new behavior and output format.

This commit introduces a **new capability** to **log `dynamic_inputs_bytes`** during **dynamic lambda execution** for enhanced telemetry. It achieves this by implementing a new `size` method for `ArtifactValue` and `ActionDirectoryMember` within the `buck2_execute` module, enabling the calculation of the total byte size of artifacts and their dependencies. The calculated `dynamic_inputs_bytes` value is then added to and recorded in the `DynamicLambdaStart` **protocol buffer message** in `buck2_data`. This **observability enhancement** provides crucial data for **dynamic analysis**, offering better insights into the resource consumption of dynamic inputs.

This commit introduces a **new telemetry capability** to trace the full lifecycle of a sampled subset of **action digests** within the **remote execution system**. It adds a new `ActionDigestTrace` event to `buck2_data/data.proto` and integrates sampling logic in `app/buck2_execute/src/re/digest_sampler.rs` and `app/buck2_execute/src/re/client.rs` to log operations like cache hits, misses, and uploads. This **observability feature** allows for detailed analysis of how **Time-To-Live (TTL)** settings impact build speed and capacity, with events streamed via the `scribe` sink. Comprehensive **end-to-end tests** in `tests/core/executor/test_action_digest_trace.py` validate the new tracing functionality.

This commit performs a **refactoring** by **renaming** the `DeferredEvaluationEnd` concept to `DynamicLambdaEnd` to better reflect its actual purpose. This change impacts the **dynamic action execution** subsystem, specifically updating the usage within the `prepare_and_execute_lambda` function in `buck2_action_impl`. Concurrently, the corresponding message in the `buck2_data` protocol definition is renamed from `DeferredEvaluationEnd` to `DynamicLambdaEnd`, and its reference within `SpanEndEvent` is updated. This ensures consistency and improved clarity in how dynamic lambda completion events are represented and serialized across the system.

This commit **enhances the user experience** by **improving the help documentation** for the **`buck2 run` command**. It explicitly clarifies the use of `--` to separate arguments intended for `buck2` itself from those meant for the executed target, updating the usage string in `app/buck2_client/src/commands/run.rs`. A corresponding **golden file test** for `buck2-help-run.golden.txt` was also updated to reflect this new, clearer explanation. This **documentation improvement** ensures users can more easily understand how to correctly pass arguments to their executables.

This commit performs a **refactoring** of the **Starlark runtime environment** by centralizing the logic for constructing `Ty` instances. A new `make_type` function is introduced within `NativeCallableComponents` to encapsulate this type creation. Consequently, the `add_native_function` and `add_native_method` methods in the **globals and methods registration modules** are updated to utilize this new helper. This change removes redundant type construction logic, an `unwrap` call, and addresses a `TODO` comment, significantly improving code organization and maintainability for how native callable types are defined.

This commit **refactors** the application of the **C++ generic error handler** (`cxx_generic_error_handler`) within the build system to ensure it is applied consistently and exactly once across the entire `fbsource` codebase. The application logic is moved from `cxx_toolchain_infos` in `prelude/cxx/cxx_toolchain_types.bzl`, where it could be redundantly invoked, to the **universal toolchain**. This **maintenance** change removes the now-obsolete `cxx_combined_error_handler` and updates `cxx_toolchain_infos` to directly reference `cxx_error_handler`. The change **improves the robustness and correctness** of the C++ build system's error handling setup by preventing potential duplicate definitions, and includes **documentation updates** for `cxx_generic_error_handler` in `prelude/cxx/cxx_error_handler.bzl`.

This commit **refactors** the **C++ library linking strategy** within the `prelude/cxx/cxx_library.bzl` macro definitions. It renames and clarifies the `cxx_attr_link_strategy` and introduces a new helper function, `_link_strategy_for_some_shared_links`, to encapsulate complex logic for determining shared library links. Functions such as `cxx_library_parameterized` and `_get_shared_library_links` are updated to utilize this new helper, streamlining the link strategy determination. This **refactoring** improves the maintainability and clarity of the **C++ build system's linking behavior**.

This commit **enables the `third-party-buck` module to utilize modifier-based configuration overrides** for its default target platforms. It **modifies the `set_cfg_modifiers` function** in `prelude/cfg/modifier/set_cfg_modifiers.bzl` to bypass a previous restriction, allowing its usage within `third-party-buck` module paths. This **platform configuration adjustment** provides a crucial mechanism for package-level overrides of the `tp2` platform, addressing limitations previously encountered with `cxx platforms`. The change significantly improves flexibility in configuring third-party dependencies by allowing more granular and modifier-based control over platform settings.