subscriber: remove `Subscribe` impls for `Arc`s #1649

hawkw · 2021-10-19T17:20:29Z

Implementing Subscribe for Arcs, which are immutable, breaks the
ability to implement Subscribe::on_layer with a mutable reference.
This is necessary for per-layer filtering. See
#1576 (comment) for
details. Therefore, the Layer impls for Arcs should not be used.

In 0.3, we have the opportunity to remove these APIs. Therefore, this PR
removes them.

Implementing `Subscribe` for `Arc`s, which are immutable, breaks the ability to implement `Subscribe::on_layer` with a mutable reference. This is necessary for per-layer filtering. See #1576 (comment) for details. Therefore, the `Layer` impls for `Arc`s should not be used. In 0.3, we have the opportunity to remove these APIs. Therefore, this PR removes them.

hawkw · 2021-10-19T17:24:51Z

cc @jsgf

Depends on #1649 ## Motivation Presently, the `tracing-subscriber` crate requires the Rust standard library and doesn't build with `#![no_std]` targets. For the most part, this is fine, as much of `tracing-subscriber` inherently depends on `std` APIs. However, `tracing-subscriber` also contains some key abstractions that are necessary for interoperability: the `Subscriber` and `LookupSpan` traits. Since these traits are in `tracing-subscriber`, `no-std` users cannot currently access them. Some of the other utilities in this crate, such as the field visitor combinators, may also be useful for `#![no_std]` projects. ## Solution This branch adds "std" and "alloc" feature flags to `tracing-subscriber`, for conditionally enabling `libstd` and `liballoc`, respectively. The `registry`, `fmt`, `EnvFilter`, and `reload` APIs all require libstd, and cannot be implemented without it, but the core `Subscribe` and `LookupSpan` traits are now available with `#![no_std]`. Fixes #999 Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Implementing `Layer` for `Arc`s, which are immutable, breaks the ability to implement `Layer::on_layer` with a mutable reference. This is necessary for per-layer filtering. See #1576 (comment) for details. Therefore, the `Layer` impls for `Arc`s should not be used. In 0.3, we have the opportunity to remove these APIs. Therefore, this PR removes them.

Backports #1648 from `master`. Depends on #1649 ## Motivation Presently, the `tracing-subscriber` crate requires the Rust standard library and doesn't build with `#![no_std]` targets. For the most part, this is fine, as much of `tracing-subscriber` inherently depends on `std` APIs. However, `tracing-subscriber` also contains some key abstractions that are necessary for interoperability: the `Layer` and `LookupSpan` traits. Since these traits are in `tracing-subscriber`, `no-std` users cannot currently access them. Some of the other utilities in this crate, such as the field visitor combinators, may also be useful for `#![no_std]` projects. ## Solution This branch adds "std" and "alloc" feature flags to `tracing-subscriber`, for conditionally enabling `libstd` and `liballoc`, respectively. The `registry`, `fmt`, `EnvFilter`, and `reload` APIs all require libstd, and cannot be implemented without it, but the core `Layer` and `LookupSpan` traits are now available with `#![no_std]`. Fixes #999 Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Implementing `Layer` for `Arc`s, which are immutable, breaks the ability to implement `Layer::on_layer` with a mutable reference. This is necessary for per-layer filtering. See #1576 (comment) for details. Therefore, the `Layer` impls for `Arc`s should not be used. In 0.3, we have the opportunity to remove these APIs. Therefore, this PR removes them.

Backports #1648 from `master`. Depends on #1649 ## Motivation Presently, the `tracing-subscriber` crate requires the Rust standard library and doesn't build with `#![no_std]` targets. For the most part, this is fine, as much of `tracing-subscriber` inherently depends on `std` APIs. However, `tracing-subscriber` also contains some key abstractions that are necessary for interoperability: the `Layer` and `LookupSpan` traits. Since these traits are in `tracing-subscriber`, `no-std` users cannot currently access them. Some of the other utilities in this crate, such as the field visitor combinators, may also be useful for `#![no_std]` projects. ## Solution This branch adds "std" and "alloc" feature flags to `tracing-subscriber`, for conditionally enabling `libstd` and `liballoc`, respectively. The `registry`, `fmt`, `EnvFilter`, and `reload` APIs all require libstd, and cannot be implemented without it, but the core `Layer` and `LookupSpan` traits are now available with `#![no_std]`. Fixes #999 Signed-off-by: Eliza Weisman <eliza@buoyant.io>

@Folyd

# 0.3.0 (Oct 22, 2021) This is a breaking release of `tracing-subscriber`. The primary breaking change in this release is the removal of the dependency on the [`chrono` crate], due to [RUSTSEC-2020-0159]. To replace `chrono`, support is added for formatting timestamps using the [`time` crate] instead. In addition, this release includes a number of other breaking API changes, such as adding (limited) support for `#![no_std]` targets, removing previously deprecated APIs, and more. ### Breaking Changes - Removed APIs deprecated in the v0.2.x release series. - Renamed `Layer::new_span` to `Layer::on_new_span` ([#1674]) - Removed `Layer` impl for `Arc<L: Layer<S>>` and `Arc<dyn Layer<S> + ...>` ([#1649]) - Replaced the [`chrono` crate] with the [`time` crate] for timestamp formatting, to resolve [RUSTSEC-2020-0159] ([#1646]) - Removed `json` and `env-filter` from default features. They must now be enabled explictly ([#1647]) - Changed `FormatEvent::format_event` and `FormatFields::format_fields` trait methods to take a `Writer` type, rather than a `&mut dyn fmt::Write` trait object ([#1661]) - Changed the signature of the `MakeWriter` trait by adding a lifetime parameter ([#781]) ### Changed - **layer**: Renamed `Layer::new_span` to `Layer::on_new_span` ([#1674]) - **fmt**: Changed `FormatEvent::format_event` and `FormatFields::format_fields` trait methods to take a `Writer` type, rather than a `&mut dyn fmt::Write` trait object ([#1661]) - **json**, **env-filter**: `json` and `env-filter` feature flags are no longer enabled by default ([#1647]) ### Removed - Removed deprecated `CurrentSpan` type ([#1320]) - **registry**: Removed deprecated `SpanRef::parents` iterator, replaced by `SpanRef::scope` in [#1431] ([#1648)]) - **layer**: Removed deprecated `Context::scope` iterator, replaced by `Context::span_scope` and `Context::event_scope` in [#1431] and [#1434] ([#1648)]) - **layer**: Removed `Layer` impl for `Arc<L: Layer<S>>` and `Arc<dyn Layer<S> + ...>`. These interfere with per-layer filtering. ([#1649]) - **fmt**: Removed deprecated `LayerBuilder` type ([#1673]) - **fmt**: Removed `fmt::Layer::on_event` (renamed to `fmt::Layer::fmt_event`) ([#1673]) - **fmt**, **chrono**: Removed the `chrono` feature flag and APIs for using the [`chrono` crate] for timestamp formatting ([#1646]) ### Added - **fmt**, **time**: `LocalTime` and `UtcTime` types for formatting timestamps using the [`time` crate] ([#1646]) - **fmt**: Added a lifetime parameter to the `MakeWriter` trait, allowing it to return a borrowed writer. This enables implementations of `MakeWriter` for types such as `Mutex<T: io::Write>` and `std::fs::File`. ([#781]) - **env-filter**: Documentation improvements ([#1637]) - Support for some APIs on `#![no_std]` targets, by disabling the `std` feature flag ([#1660]) Thanks to @Folyd and @nmathewson for contributing to this release! [#1320]: #1320 [#1673]: #1673 [#1674]: #1674 [#1646]: #1646 [#1647]: #1647 [#1648]: #1648 [#1649]: #1649 [#1660]: #1660 [#1661]: #1661 [#1431]: #1431 [#1434]: #1434 [#781]: #781 [`chrono` crate]: https://crates.io/crates/chrono [`time` crate]: https://crates.io/crates/time [RUSTSEC-2020-0159]: https://rustsec.org/advisories/RUSTSEC-2020-0159.html

@Folyd

# 0.3.0 (Oct 22, 2021) This is a breaking release of `tracing-subscriber`. The primary breaking change in this release is the removal of the dependency on the [`chrono` crate], due to [RUSTSEC-2020-0159]. To replace `chrono`, support is added for formatting timestamps using the [`time` crate] instead. In addition, this release includes a number of other breaking API changes, such as adding (limited) support for `#![no_std]` targets, removing previously deprecated APIs, and more. ### Breaking Changes - Removed APIs deprecated in the v0.2.x release series. - Renamed `Layer::new_span` to `Layer::on_new_span` ([#1674]) - Removed `Layer` impl for `Arc<L: Layer<S>>` and `Arc<dyn Layer<S> + ...>` ([#1649]) - Replaced the [`chrono` crate] with the [`time` crate] for timestamp formatting, to resolve [RUSTSEC-2020-0159] ([#1646]) - Removed `json` and `env-filter` from default features. They must now be enabled explictly ([#1647]) - Changed `FormatEvent::format_event` and `FormatFields::format_fields` trait methods to take a `Writer` type, rather than a `&mut dyn fmt::Write` trait object ([#1661]) - Changed the signature of the `MakeWriter` trait by adding a lifetime parameter ([#781]) ### Changed - **layer**: Renamed `Layer::new_span` to `Layer::on_new_span` ([#1674]) - **fmt**: Changed `FormatEvent::format_event` and `FormatFields::format_fields` trait methods to take a `Writer` type, rather than a `&mut dyn fmt::Write` trait object ([#1661]) - **json**, **env-filter**: `json` and `env-filter` feature flags are no longer enabled by default ([#1647]) ### Removed - Removed deprecated `CurrentSpan` type ([#1320]) - **registry**: Removed deprecated `SpanRef::parents` iterator, replaced by `SpanRef::scope` in [#1431] ([#1648)]) - **layer**: Removed deprecated `Context::scope` iterator, replaced by `Context::span_scope` and `Context::event_scope` in [#1431] and [#1434] ([#1648)]) - **layer**: Removed `Layer` impl for `Arc<L: Layer<S>>` and `Arc<dyn Layer<S> + ...>`. These interfere with per-layer filtering. ([#1649]) - **fmt**: Removed deprecated `LayerBuilder` type ([#1673]) - **fmt**: Removed `fmt::Layer::on_event` (renamed to `fmt::Layer::fmt_event`) ([#1673]) - **fmt**, **chrono**: Removed the `chrono` feature flag and APIs for using the [`chrono` crate] for timestamp formatting ([#1646]) ### Added - **fmt**, **time**: `LocalTime` and `UtcTime` types for formatting timestamps using the [`time` crate] ([#1646]) - **fmt**: Added a lifetime parameter to the `MakeWriter` trait, allowing it to return a borrowed writer. This enables implementations of `MakeWriter` for types such as `Mutex<T: io::Write>` and `std::fs::File`. ([#781]) - **env-filter**: Documentation improvements ([#1637]) - Support for some APIs on `#![no_std]` targets, by disabling the `std` feature flag ([#1660]) Thanks to @Folyd and @nmathewson for contributing to this release! [#1320]: #1320 [#1673]: #1673 [#1674]: #1674 [#1646]: #1646 [#1647]: #1647 [#1648]: #1648 [#1649]: #1649 [#1660]: #1660 [#1661]: #1661 [#1431]: #1431 [#1434]: #1434 [#781]: #781 [`chrono` crate]: https://crates.io/crates/chrono [`time` crate]: https://crates.io/crates/time [RUSTSEC-2020-0159]: https://rustsec.org/advisories/RUSTSEC-2020-0159.html Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Implementing `Layer` for `Arc`s, which are immutable, breaks the ability to implement `Layer::on_layer` with a mutable reference. This is necessary for per-layer filtering. See #1576 (comment) for details. Therefore, the `Layer` impls for `Arc`s should not be used. In 0.3, we have the opportunity to remove these APIs. Therefore, this PR removes them.

Backports #1648 from `master`. Depends on #1649 ## Motivation Presently, the `tracing-subscriber` crate requires the Rust standard library and doesn't build with `#![no_std]` targets. For the most part, this is fine, as much of `tracing-subscriber` inherently depends on `std` APIs. However, `tracing-subscriber` also contains some key abstractions that are necessary for interoperability: the `Layer` and `LookupSpan` traits. Since these traits are in `tracing-subscriber`, `no-std` users cannot currently access them. Some of the other utilities in this crate, such as the field visitor combinators, may also be useful for `#![no_std]` projects. ## Solution This branch adds "std" and "alloc" feature flags to `tracing-subscriber`, for conditionally enabling `libstd` and `liballoc`, respectively. The `registry`, `fmt`, `EnvFilter`, and `reload` APIs all require libstd, and cannot be implemented without it, but the core `Layer` and `LookupSpan` traits are now available with `#![no_std]`. Fixes #999

@Folyd

# 0.3.0 (Oct 22, 2021) This is a breaking release of `tracing-subscriber`. The primary breaking change in this release is the removal of the dependency on the [`chrono` crate], due to [RUSTSEC-2020-0159]. To replace `chrono`, support is added for formatting timestamps using the [`time` crate] instead. In addition, this release includes a number of other breaking API changes, such as adding (limited) support for `#![no_std]` targets, removing previously deprecated APIs, and more. ### Breaking Changes - Removed APIs deprecated in the v0.2.x release series. - Renamed `Layer::new_span` to `Layer::on_new_span` ([#1674]) - Removed `Layer` impl for `Arc<L: Layer<S>>` and `Arc<dyn Layer<S> + ...>` ([#1649]) - Replaced the [`chrono` crate] with the [`time` crate] for timestamp formatting, to resolve [RUSTSEC-2020-0159] ([#1646]) - Removed `json` and `env-filter` from default features. They must now be enabled explictly ([#1647]) - Changed `FormatEvent::format_event` and `FormatFields::format_fields` trait methods to take a `Writer` type, rather than a `&mut dyn fmt::Write` trait object ([#1661]) - Changed the signature of the `MakeWriter` trait by adding a lifetime parameter ([#781]) ### Changed - **layer**: Renamed `Layer::new_span` to `Layer::on_new_span` ([#1674]) - **fmt**: Changed `FormatEvent::format_event` and `FormatFields::format_fields` trait methods to take a `Writer` type, rather than a `&mut dyn fmt::Write` trait object ([#1661]) - **json**, **env-filter**: `json` and `env-filter` feature flags are no longer enabled by default ([#1647]) ### Removed - Removed deprecated `CurrentSpan` type ([#1320]) - **registry**: Removed deprecated `SpanRef::parents` iterator, replaced by `SpanRef::scope` in [#1431] ([#1648)]) - **layer**: Removed deprecated `Context::scope` iterator, replaced by `Context::span_scope` and `Context::event_scope` in [#1431] and [#1434] ([#1648)]) - **layer**: Removed `Layer` impl for `Arc<L: Layer<S>>` and `Arc<dyn Layer<S> + ...>`. These interfere with per-layer filtering. ([#1649]) - **fmt**: Removed deprecated `LayerBuilder` type ([#1673]) - **fmt**: Removed `fmt::Layer::on_event` (renamed to `fmt::Layer::fmt_event`) ([#1673]) - **fmt**, **chrono**: Removed the `chrono` feature flag and APIs for using the [`chrono` crate] for timestamp formatting ([#1646]) ### Added - **fmt**, **time**: `LocalTime` and `UtcTime` types for formatting timestamps using the [`time` crate] ([#1646]) - **fmt**: Added a lifetime parameter to the `MakeWriter` trait, allowing it to return a borrowed writer. This enables implementations of `MakeWriter` for types such as `Mutex<T: io::Write>` and `std::fs::File`. ([#781]) - **env-filter**: Documentation improvements ([#1637]) - Support for some APIs on `#![no_std]` targets, by disabling the `std` feature flag ([#1660]) Thanks to @Folyd and @nmathewson for contributing to this release! [#1320]: tokio-rs/tracing#1320 [#1673]: tokio-rs/tracing#1673 [#1674]: tokio-rs/tracing#1674 [#1646]: tokio-rs/tracing#1646 [#1647]: tokio-rs/tracing#1647 [#1648]: tokio-rs/tracing#1648 [#1649]: tokio-rs/tracing#1649 [#1660]: tokio-rs/tracing#1660 [#1661]: tokio-rs/tracing#1661 [#1431]: tokio-rs/tracing#1431 [#1434]: tokio-rs/tracing#1434 [#781]: tokio-rs/tracing#781 [`chrono` crate]: https://crates.io/crates/chrono [`time` crate]: https://crates.io/crates/time [RUSTSEC-2020-0159]: https://rustsec.org/advisories/RUSTSEC-2020-0159.html Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Implementing `Layer` for `Arc`s, which are immutable, breaks the ability to implement `Layer::on_layer` with a mutable reference. This is necessary for per-layer filtering. See tokio-rs#1576 (comment) for details. Therefore, the `Layer` impls for `Arc`s should not be used. In 0.3, we have the opportunity to remove these APIs. Therefore, this PR removes them.

Backports tokio-rs#1648 from `master`. Depends on tokio-rs#1649 ## Motivation Presently, the `tracing-subscriber` crate requires the Rust standard library and doesn't build with `#![no_std]` targets. For the most part, this is fine, as much of `tracing-subscriber` inherently depends on `std` APIs. However, `tracing-subscriber` also contains some key abstractions that are necessary for interoperability: the `Layer` and `LookupSpan` traits. Since these traits are in `tracing-subscriber`, `no-std` users cannot currently access them. Some of the other utilities in this crate, such as the field visitor combinators, may also be useful for `#![no_std]` projects. ## Solution This branch adds "std" and "alloc" feature flags to `tracing-subscriber`, for conditionally enabling `libstd` and `liballoc`, respectively. The `registry`, `fmt`, `EnvFilter`, and `reload` APIs all require libstd, and cannot be implemented without it, but the core `Layer` and `LookupSpan` traits are now available with `#![no_std]`. Fixes tokio-rs#999 Signed-off-by: Eliza Weisman <eliza@buoyant.io>

@Folyd

# 0.3.0 (Oct 22, 2021) This is a breaking release of `tracing-subscriber`. The primary breaking change in this release is the removal of the dependency on the [`chrono` crate], due to [RUSTSEC-2020-0159]. To replace `chrono`, support is added for formatting timestamps using the [`time` crate] instead. In addition, this release includes a number of other breaking API changes, such as adding (limited) support for `#![no_std]` targets, removing previously deprecated APIs, and more. ### Breaking Changes - Removed APIs deprecated in the v0.2.x release series. - Renamed `Layer::new_span` to `Layer::on_new_span` ([tokio-rs#1674]) - Removed `Layer` impl for `Arc<L: Layer<S>>` and `Arc<dyn Layer<S> + ...>` ([tokio-rs#1649]) - Replaced the [`chrono` crate] with the [`time` crate] for timestamp formatting, to resolve [RUSTSEC-2020-0159] ([tokio-rs#1646]) - Removed `json` and `env-filter` from default features. They must now be enabled explictly ([tokio-rs#1647]) - Changed `FormatEvent::format_event` and `FormatFields::format_fields` trait methods to take a `Writer` type, rather than a `&mut dyn fmt::Write` trait object ([tokio-rs#1661]) - Changed the signature of the `MakeWriter` trait by adding a lifetime parameter ([tokio-rs#781]) ### Changed - **layer**: Renamed `Layer::new_span` to `Layer::on_new_span` ([tokio-rs#1674]) - **fmt**: Changed `FormatEvent::format_event` and `FormatFields::format_fields` trait methods to take a `Writer` type, rather than a `&mut dyn fmt::Write` trait object ([tokio-rs#1661]) - **json**, **env-filter**: `json` and `env-filter` feature flags are no longer enabled by default ([tokio-rs#1647]) ### Removed - Removed deprecated `CurrentSpan` type ([tokio-rs#1320]) - **registry**: Removed deprecated `SpanRef::parents` iterator, replaced by `SpanRef::scope` in [tokio-rs#1431] ([tokio-rs#1648)]) - **layer**: Removed deprecated `Context::scope` iterator, replaced by `Context::span_scope` and `Context::event_scope` in [tokio-rs#1431] and [tokio-rs#1434] ([tokio-rs#1648)]) - **layer**: Removed `Layer` impl for `Arc<L: Layer<S>>` and `Arc<dyn Layer<S> + ...>`. These interfere with per-layer filtering. ([tokio-rs#1649]) - **fmt**: Removed deprecated `LayerBuilder` type ([tokio-rs#1673]) - **fmt**: Removed `fmt::Layer::on_event` (renamed to `fmt::Layer::fmt_event`) ([tokio-rs#1673]) - **fmt**, **chrono**: Removed the `chrono` feature flag and APIs for using the [`chrono` crate] for timestamp formatting ([tokio-rs#1646]) ### Added - **fmt**, **time**: `LocalTime` and `UtcTime` types for formatting timestamps using the [`time` crate] ([tokio-rs#1646]) - **fmt**: Added a lifetime parameter to the `MakeWriter` trait, allowing it to return a borrowed writer. This enables implementations of `MakeWriter` for types such as `Mutex<T: io::Write>` and `std::fs::File`. ([tokio-rs#781]) - **env-filter**: Documentation improvements ([tokio-rs#1637]) - Support for some APIs on `#![no_std]` targets, by disabling the `std` feature flag ([tokio-rs#1660]) Thanks to @Folyd and @nmathewson for contributing to this release! [tokio-rs#1320]: tokio-rs#1320 [tokio-rs#1673]: tokio-rs#1673 [tokio-rs#1674]: tokio-rs#1674 [tokio-rs#1646]: tokio-rs#1646 [tokio-rs#1647]: tokio-rs#1647 [tokio-rs#1648]: tokio-rs#1648 [tokio-rs#1649]: tokio-rs#1649 [tokio-rs#1660]: tokio-rs#1660 [tokio-rs#1661]: tokio-rs#1661 [tokio-rs#1431]: tokio-rs#1431 [tokio-rs#1434]: tokio-rs#1434 [tokio-rs#781]: tokio-rs#781 [`chrono` crate]: https://crates.io/crates/chrono [`time` crate]: https://crates.io/crates/time [RUSTSEC-2020-0159]: https://rustsec.org/advisories/RUSTSEC-2020-0159.html Signed-off-by: Eliza Weisman <eliza@buoyant.io>

hawkw requested review from davidbarsky and a team as code owners October 19, 2021 17:20

hawkw mentioned this pull request Oct 19, 2021

subscriber: add minimal #![no_std] support #1648

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davidbarsky approved these changes Oct 19, 2021

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hawkw merged commit ae37598 into master Oct 19, 2021

hawkw deleted the eliza/rm-arc-impls branch October 19, 2021 17:26

hawkw mentioned this pull request Oct 21, 2021

subscriber: backport tracing-subscriber v0.3 changes #1666

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hawkw mentioned this pull request Oct 22, 2021

subscriber: prepare to release v0.3.0 #1677

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davidbarsky mentioned this pull request Sep 26, 2023

chore: backport roughly a year's worth of changes #2728

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subscriber: remove `Subscribe` impls for `Arc`s #1649

subscriber: remove `Subscribe` impls for `Arc`s #1649

hawkw commented Oct 19, 2021

hawkw commented Oct 19, 2021

subscriber: remove Subscribe impls for Arcs #1649

subscriber: remove Subscribe impls for Arcs #1649

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hawkw commented Oct 19, 2021

hawkw commented Oct 19, 2021

subscriber: remove `Subscribe` impls for `Arc`s #1649

subscriber: remove `Subscribe` impls for `Arc`s #1649