Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

This picks up upstream changes from hawkw/tokio-trace-prototype#168.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Apparently we were missing this. I wrote a doc example that used it and
was surprised when it didn't work.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Looks like this was overlooked in hawkw/tokio-trace-prototype#168.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

I didn't want these to be covered only by doctests.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

The new tests revealed these.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

I think this was originally intended to avoid the benchmarks getting
optimized away, but that doesn't seem to be a problem.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Thanks to @seanmonstar.

Co-Authored-By: hawkw <eliza@buoyant.io>

Thanks to @davidbarsky!

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

As suggested by @seanmonstar.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

As suggested by @seanmonstar.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Co-Authored-By: hawkw <eliza@buoyant.io>

Co-Authored-By: hawkw <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

It should eventually live in the `tokio-trace-subscriber` crate.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

(like the docs say it does)

thanks to @stjepang!

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

This shaves about 1-2ns off the disabled span benchmarks

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

This lets us completely skip `Span::new` in this case. This brings the benchmarks for the disabled case back into parity with `log`.

Before:
```
     Running target/release/deps/no_subscriber-1064195d321c8640

running 5 tests
test bench_1_atomic_load              ... bench:           0 ns/iter (+/- 0)
test bench_costly_field_no_subscriber ... bench:           6 ns/iter (+/- 0)
test bench_log_no_logger              ... bench:           0 ns/iter (+/- 0)
test bench_no_span_no_subscriber      ... bench:           0 ns/iter (+/- 0)
test bench_span_no_subscriber         ... bench:           6 ns/iter (+/- 0)

test result: ok. 0 passed; 0 failed; 0 ignored; 5 measured; 0 filtered out

     Running target/release/deps/subscriber-7319775649c47f41

running 4 tests
test span_no_fields          ... bench:          37 ns/iter (+/- 10)
test span_repeatedly         ... bench:       5,626 ns/iter (+/- 812)
test span_with_fields        ... bench:         101 ns/iter (+/- 20)
test span_with_fields_record ... bench:       1,035 ns/iter (+/- 171)

test result: ok. 0 passed; 0 failed; 0 ignored; 4 measured; 0 filtered out
```
After:
```
     Running target/release/deps/no_subscriber-1064195d321c8640

running 5 tests
test bench_1_atomic_load              ... bench:           0 ns/iter (+/- 0)
test bench_costly_field_no_subscriber ... bench:           0 ns/iter (+/- 0)
test bench_log_no_logger              ... bench:           0 ns/iter (+/- 0)
test bench_no_span_no_subscriber      ... bench:           0 ns/iter (+/- 0)
test bench_span_no_subscriber         ... bench:           0 ns/iter (+/- 0)

test result: ok. 0 passed; 0 failed; 0 ignored; 5 measured; 0 filtered out

     Running target/release/deps/subscriber-7319775649c47f41

running 4 tests
test span_no_fields          ... bench:          36 ns/iter (+/- 8)
test span_repeatedly         ... bench:       5,381 ns/iter (+/- 1,075)
test span_with_fields        ... bench:         110 ns/iter (+/- 19)
test span_with_fields_record ... bench:       1,019 ns/iter (+/- 247)

test result: ok. 0 passed; 0 failed; 0 ignored; 4 measured; 0 filtered out
```

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Ugh, code duplication :/

This branch reworks `tokio-trace`'s field recording APIs to improve
performance in cases where field values are provided in batches. 

`tokio-trace` supports recording values for span fields either when the
span is constructed, or at any point during its lifetime. In order to
support this, the current implementation represents each field value
recorded with a separate call to a `Subscriber::record_$TYPE` function.
This can incur significant overhead --- for example, if the span data is
stored behind a mutex, every call to `record` must reacquire the lock. 

Providing most or all of the fields on a span up-front as it is
constructed is likely to be the common case, but in the current design,
this use-case has to pay performance costs in order to support the less
common case of adding values post-initialization. Even in situations
where some field values are unknown, if a majority are recorded at
construction-time, each individual value takes a separate trip through
the `record` pipeline.

This branch rewrites this API so that all field recording is done by a
`ValueSet` type, which groups together multiple values. A subscriber may
pass an implementation of `Record` to the `ValueSet`'s `record`
function, which will record all the provided values with that recorder.
When a span is constructed, the `Subscriber::new_span` method is called
with a `ValueSet` containing all the fields provided to the `span!`
macro, and additional fields may be recorded either individually or in
batches.

In addition, the previous implementation of `Event`s on top of `Span`s
has been removed and replaced with a new `Event` type which goes through
a separate `Subscriber::event` function. Events are always known to have
all their values at construction time, since the event cannot live long
enough to have more values added. Thus, an `Event` also contains a
`ValueSet`.

I've added new test-support code for expecting certain fields to be
recorded by spans and events, and written new tests to cover this
behaviour. I've also updated the example code, and my experience doing
so suggests that the new API is also somewhat more ergonomic to use.

These changes result in significant improvement on the benchmark that
simulates recording multiple fields on a span 
(`bench_span_with_fields_record`).

Before:
```
     Running target/release/deps/no_subscriber-a6af9f5aa4934184

running 5 tests
test bench_1_atomic_load              ... bench:           0 ns/iter (+/- 0)
test bench_costly_field_no_subscriber ... bench:           0 ns/iter (+/- 0)
test bench_log_no_logger              ... bench:           0 ns/iter (+/- 0)
test bench_no_span_no_subscriber      ... bench:           0 ns/iter (+/- 0)
test bench_span_no_subscriber         ... bench:           0 ns/iter (+/- 0)

test result: ok. 0 passed; 0 failed; 0 ignored; 5 measured; 0 filtered out

     Running target/release/deps/subscriber-ba753dc1d87e480d

running 4 tests
test span_no_fields          ... bench:          41 ns/iter (+/- 5)
test span_repeatedly         ... bench:       5,418 ns/iter (+/- 658)
test span_with_fields        ... bench:         110 ns/iter (+/- 42)
test span_with_fields_record ... bench:       1,047 ns/iter (+/- 240)

test result: ok. 0 passed; 0 failed; 0 ignored; 4 measured; 0 filtered out
```

After:
```
     Running target/release/deps/no_subscriber-611d60b262fbbcfb

running 5 tests
test bench_1_atomic_load              ... bench:           0 ns/iter (+/- 0)
test bench_costly_field_no_subscriber ... bench:           1 ns/iter (+/- 0)
test bench_log_no_logger              ... bench:           0 ns/iter (+/- 0)
test bench_no_span_no_subscriber      ... bench:           0 ns/iter (+/- 0)
test bench_span_no_subscriber         ... bench:           0 ns/iter (+/- 0)

test result: ok. 0 passed; 0 failed; 0 ignored; 5 measured; 0 filtered out

     Running target/release/deps/subscriber-7a1279c84c0d50ff

running 4 tests
test span_no_fields          ... bench:          37 ns/iter (+/- 9)
test span_repeatedly         ... bench:       4,502 ns/iter (+/- 712)
test span_with_fields        ... bench:          54 ns/iter (+/- 17)
test span_with_fields_record ... bench:         364 ns/iter (+/- 38)

test result: ok. 0 passed; 0 failed; 0 ignored; 4 measured; 0 filtered out
```

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

These have to be in `-core` due to the orphan rules, but seem very
handy.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

The `trace_dbg!` macro requires this.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

See also tokio-rs/tracing@5296a4c

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Trailing commas are optional when fields are included, and when fields
are delimited from the format string for the message.

Before these would error:
```
event!(tokio_trace::Level::DEBUG, foo = 3, bar = 3,);
event!(tokio_trace::Level::DEBUG, { foo = 2, bar = 78, }, "baz");
```

Now they do not. Tests have been extended.

Signed-off-by: Kevin Leimkuhler <kevinl@buoyant.io>

* tokio-trace: Extend `span!` rules

Add the ability to define a target and log level for
individual spans.

`level: ...` must be included since both `$lvl` and `$name` are `expr`.

The macro tests and documentation tests have been extended.

Signed-off-by: Kevin Leimkuhler <kevinl@buoyant.io>

* Add additional `span!` test

Change default log level of `span!` to `TRACE` to reflect the default
level used in `callsite!`.

Signed-off-by: Kevin Leimkuhler <kevinl@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Looks like RLS missed a couple uses

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

Signed-off-by: Eliza Weisman <eliza@buoyant.io>