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

hawkw · 2021-10-19T17:09:01Z

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

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.

Signed-off-by: Eliza Weisman <[email protected]>

… into eliza/subscriber-no-std

tracing-subscriber/Cargo.toml

apparently this behaves differently on 1.42.0, so we can't use the macro here... Signed-off-by: Eliza Weisman <[email protected]>

Signed-off-by: Eliza Weisman <[email protected]>

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 <[email protected]>

@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 <[email protected]>

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 <[email protected]>

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 <[email protected]>

@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 <[email protected]>

hawkw requested a review from davidbarsky October 19, 2021 17:09

hawkw requested a review from a team as a code owner October 19, 2021 17:09

hawkw added 5 commits October 19, 2021 10:13

docs

a2998fa

Signed-off-by: Eliza Weisman <[email protected]>

subscriber: add std feature flags

810371b

Signed-off-by: Eliza Weisman <[email protected]>

subscriber: actually use libcore

301c7f0

Signed-off-by: Eliza Weisman <[email protected]>

fixup tests

88bbc55

hawkw force-pushed the eliza/subscriber-no-std branch from 530624a to 88bbc55 Compare October 19, 2021 17:22

hawkw changed the base branch from master to eliza/rm-arc-impls October 19, 2021 17:22

davidbarsky approved these changes Oct 19, 2021

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Base automatically changed from eliza/rm-arc-impls to master October 19, 2021 17:26

hawkw added 3 commits October 19, 2021 10:28

Merge branch 'master' into eliza/subscriber-no-std

b1de82a

missing std feature flags

3b3a8d5

Signed-off-by: Eliza Weisman <[email protected]>

Merge branch 'eliza/subscriber-no-std' of github.com:tokio-rs/tracing…

d2222dd

… into eliza/subscriber-no-std

hawkw commented Oct 19, 2021

View reviewed changes

tracing-subscriber/Cargo.toml Outdated Show resolved Hide resolved

hawkw added 6 commits October 19, 2021 10:34

Update tracing-subscriber/Cargo.toml

0e5cdde

fix extensions method feature flagging on 1.42.0

cf73be9

apparently this behaves differently on 1.42.0, so we can't use the macro here... Signed-off-by: Eliza Weisman <[email protected]>

we just can't use the macro on methods i guess

dd63fc6

Signed-off-by: Eliza Weisman <[email protected]>

fix unused warning

f38f0f7

Signed-off-by: Eliza Weisman <[email protected]>

awhgkjkjfljsdfgr rustfmt

69489ed

otel needs to enable std

a160181

Signed-off-by: Eliza Weisman <[email protected]>

hawkw requested a review from jtescher as a code owner October 19, 2021 21:19

jtescher approved these changes Oct 19, 2021

View reviewed changes

hawkw merged commit 226f605 into master Oct 19, 2021

hawkw deleted the eliza/subscriber-no-std branch October 19, 2021 21:55

hawkw mentioned this pull request Oct 21, 2021

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

Merged

hawkw mentioned this pull request Oct 22, 2021

subscriber: prepare to release v0.3.0 #1677

Merged

davidbarsky mentioned this pull request Sep 26, 2023

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

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

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

hawkw commented Oct 19, 2021 •

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

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

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hawkw commented Oct 19, 2021 • edited Loading

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

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

hawkw commented Oct 19, 2021 •

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