Eliza Weisman 4e56741c65
subscriber: prepare to release v0.3.0 (#1677)
# 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]: https://github.com/tokio-rs/tracing/pull/1320
[#1673]: https://github.com/tokio-rs/tracing/pull/1673
[#1674]: https://github.com/tokio-rs/tracing/pull/1674
[#1646]: https://github.com/tokio-rs/tracing/pull/1646
[#1647]: https://github.com/tokio-rs/tracing/pull/1647
[#1648]: https://github.com/tokio-rs/tracing/pull/1648
[#1649]: https://github.com/tokio-rs/tracing/pull/1649
[#1660]: https://github.com/tokio-rs/tracing/pull/1660
[#1661]: https://github.com/tokio-rs/tracing/pull/1661
[#1431]: https://github.com/tokio-rs/tracing/pull/1431
[#1434]: https://github.com/tokio-rs/tracing/pull/1434
[#781]: https://github.com/tokio-rs/tracing/pull/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>
2021-10-22 16:01:35 -07:00
..

Tracing Examples

This directory contains a collection of examples that demonstrate the use of the tracing ecosystem:

  • tracing:
    • counters: Implements a very simple metrics system to demonstrate how subscribers can consume field values as typed data.
    • sloggish: A demo Subscriber implementation that mimics the output of slog-term's Compact formatter.
  • tracing-attributes:
    • attrs-basic: A simple example of the #[instrument] attribute.
    • attrs-literal-field-names: Demonstrates using literal field names rather than rust tokens..
    • attrs-args: An example implementing a simple recursive calculation of Fibonacci numbers, to demonstrate how the #[instrument] attribute can record function arguments.
  • tracing-subscriber:
    • fmt: Demonstrates the use of the fmt module in tracing-subscriber, which provides a subscriber implementation that logs traces to the console.
    • fmt-stderr: Demonstrates overriding the output stream used by the fmt subscriber.
    • fmt-custom-field: Demonstrates overriding how the fmt subscriber formats fields on spans and events.
    • fmt-custom-event: Demonstrates overriding how the fmt subscriber formats events.
    • fmt-multiple-writers.rs: demonstrates how fmt::Layer can write to multiple destinations (in this instance, stdout and a file) simultaneously.
    • subscriber-filter: Demonstrates the tracing-subscriber::filter module, which provides a layer which adds configurable filtering to a subscriber implementation.
    • tower-load: Demonstrates how dynamically reloadable filters can be used to debug a server under load in production.
    • journald: Demonstrates how to use fmt and journald layers to output to both the terminal and the system journal.
    • toggle-layers : Demonstrates how Layers can be wrapped with an Option allowing them to be dynamically toggled.
  • tracing-futures:
    • spawny-thing: Demonstrates the use of the #[instrument] attribute macro asynchronous functions.
    • tokio-spawny-thing.rs: Similar to spawny-thingy, but with the additional demonstration instrumenting concurrent tasks created with tokio::spawn.
    • futures-proxy-server: Demonstrates the use of tracing-futures by implementing a simple proxy server, based on this example from tokio.
    • async_fn: Demonstrates how asynchronous functions can be instrumented.
    • echo: Demonstrates a tracing-instrumented variant of Tokio's echo example.
  • tracing-flame:
    • infero-flame: Demonstrates the use of tracing-flame to generate a flamegraph from spans.
  • tracing-tower:
    • tower-client: Demonstrates the use of tracing-tower to instrument a simple tower HTTP/1.1 client.
    • tower-server: Demonstrates the use of tracing-tower to instrument a simple tower HTTP/1.1 server.
  • tracing-serde:
    • serde-yak-shave: Demonstrates the use of tracing-serde by implementing a subscriber that emits trace output as JSON.
  • tracing-log:
    • hyper-echo: Demonstrates how tracing-log can be used to record unstructured logs from dependencies as tracing events, by instrumenting this example from hyper, and using tracing-log to record logs emitted by hyper.
  • tracing-opentelemetry:
    • opentelemetry: Demonstrates how tracing-opentelemetry can be used to export and visualize tracing span data.
    • opentelemetry-remote-context: Demonstrates how tracing-opentelemetry can be used to extract and inject remote context when traces span multiple systems.