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docs: fix incorrect explanation for futures and spans (#531)

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David Barsky 2020-01-11 14:12:19 -05:00 committed by Eliza Weisman
parent f7b338ed7c
commit 8214570c44
2 changed files with 10 additions and 8 deletions
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9
README.md
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@ -201,10 +201,11 @@ async {
}
```
The span `_s` will be dropped at the end of the `async` block, _not_ when the
future created by the async block is complete. In practice, this means that
the span does not live long enough to instrument the future for its entire
lifetime.
The span guard `_s` will not exit until the future generated by the `async` block is complete.
Since futures and spans can be entered and exited _multiple_ times without them completing,
the span remains entered for as long as the future exists, rather than being entered only when
it is polled, leading to very confusing and incorrect output.
For more details, see [the documentation on closing spans](https://tracing.rs/tracing/span/index.html#closing-spans).
There are two ways to instrument asynchronous code. The first is through the
[`Future::instrument`](https://docs.rs/tracing-futures/0.2.0/tracing_futures/trait.Instrument.html#method.instrument) combinator:

9
tracing/README.md
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@ -216,10 +216,11 @@ async {
}
```
The span `_s` will be dropped at the end of the `async` block, _not_ when the
future created by the async block is complete. In practice, this means that
the span does not live long enough to instrument the future for its entire
lifetime.
The span guard `_s` will not exit until the future generated by the `async` block is complete.
Since futures and spans can be entered and exited _multiple_ times without them completing,
the span remains entered for as long as the future exists, rather than being entered only when
it is polled, leading to very confusing and incorrect output.
For more details, see [the documentation on closing spans](https://tracing.rs/tracing/span/index.html#closing-spans).
There are two ways to instrument asynchronous code. The first is through the
[`Future::instrument`](https://docs.rs/tracing-futures/0.2.0/tracing_futures/trait.Instrument.html#method.instrument) combinator: