matrix_sdk_common/
tracing_timer.rs

1// Copyright 2023 The Matrix.org Foundation C.I.C.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//     http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15use ruma::time::Instant;
16use tracing::{Callsite as _, callsite::DefaultCallsite};
17
18/// A named RAII that will show on `Drop` how long its covered section took to
19/// execute.
20pub struct TracingTimer {
21    id: String,
22    callsite: &'static DefaultCallsite,
23    start: Instant,
24    level: tracing::Level,
25}
26
27#[cfg(not(tarpaulin_include))]
28impl std::fmt::Debug for TracingTimer {
29    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
30        f.debug_struct("TracingTimer").field("id", &self.id).field("start", &self.start).finish()
31    }
32}
33
34impl Drop for TracingTimer {
35    fn drop(&mut self) {
36        let elapsed = self.start.elapsed();
37
38        let enabled = tracing::level_enabled!(self.level) && {
39            let interest = self.callsite.interest();
40            !interest.is_never()
41                && tracing::__macro_support::__is_enabled(self.callsite.metadata(), interest)
42        };
43
44        if !enabled {
45            return;
46        }
47
48        let message = format!("_{}_ finished in {:?}", self.id, elapsed);
49
50        let metadata = self.callsite.metadata();
51        let fields = metadata.fields();
52        let message_field = fields.field("message").unwrap();
53        #[allow(trivial_casts)] // The compiler is lying, it can't infer this cast
54        let values = [(&message_field, Some(&message as &dyn tracing::Value))];
55
56        // This function is hidden from docs, but we have to use it
57        // because there is no other way of obtaining a `ValueSet`.
58        // It's not entirely clear why it is private. See this issue:
59        // https://github.com/tokio-rs/tracing/issues/2363
60        let values = fields.value_set(&values);
61
62        tracing::Event::dispatch(metadata, &values);
63    }
64}
65
66impl TracingTimer {
67    /// Create a new `TracingTimer`.
68    pub fn new(callsite: &'static DefaultCallsite, id: String, level: tracing::Level) -> Self {
69        Self { id, callsite, start: Instant::now(), level }
70    }
71}
72
73/// Macro to create a RAII timer that will log on `Drop` how long its covered
74/// section took to execute.
75///
76/// The tracing level can be specified as a first argument, but it's optional.
77/// If it's missing, this will use the debug level.
78///
79/// ```rust,no_run
80/// # fn do_long_computation(_x: u32) {}
81/// # fn main() {
82/// use matrix_sdk_common::timer;
83///
84/// // It's possible to specify the tracing level we want to be used for the log message on drop.
85/// {
86///     let _timer = timer!(tracing::Level::TRACE, "do long computation");
87///     // But it's optional; by default it's set to `DEBUG`.
88///     let _debug_timer = timer!("do long computation but time it in DEBUG");
89///     // The macro doesn't support parameters, use `format!()`.
90///     let _other_timer = timer!(tracing::Level::TRACE, format!("do long computation with parameter = {}", 123));
91///     do_long_computation(123);
92/// } // The log statements will happen here.
93/// # }
94/// ```
95#[macro_export]
96macro_rules! timer {
97    ($level:expr, $string:expr $(,)? ) => {{
98        static __CALLSITE: tracing::callsite::DefaultCallsite = tracing::callsite2! {
99            name: tracing::__macro_support::concat!(
100                "event ",
101                file!(),
102                ":",
103                line!(),
104            ),
105            kind: tracing::metadata::Kind::EVENT,
106            target: module_path!(),
107            level: $level,
108            fields: []
109        };
110
111        $crate::tracing_timer::TracingTimer::new(&__CALLSITE, $string.into(), $level)
112    }};
113
114    ($string:expr) => {
115        $crate::timer!(tracing::Level::DEBUG, $string)
116    };
117}
118
119#[cfg(test)]
120mod tests {
121    #[cfg(not(target_family = "wasm"))]
122    #[matrix_sdk_test_macros::async_test]
123    async fn test_timer_name() {
124        use tracing::{Level, span};
125
126        tracing::warn!("Starting test...");
127
128        mod time123 {
129            pub async fn run() {
130                let _timer_guard = timer!(tracing::Level::DEBUG, "test");
131                tokio::time::sleep(ruma::time::Duration::from_millis(123)).await;
132                // Displays: 2023-08-25T15:18:31.169498Z DEBUG
133                // matrix_sdk_common::tracing_timer::tests: _test_ finished in
134                // 124ms
135            }
136        }
137
138        time123::run().await;
139
140        let span = span!(Level::DEBUG, "le 256ms span");
141        let _guard = span.enter();
142
143        let _timer_guard = timer!("in span");
144        tokio::time::sleep(ruma::time::Duration::from_millis(256)).await;
145
146        tracing::warn!("Test about to finish.");
147        // Displays: 2023-08-25T15:18:31.427070Z DEBUG le 256ms span:
148        // matrix_sdk_common::tracing_timer::tests: in span finished in 257ms
149    }
150}
matrix_sdk_common/tracing_timer.rs

matrix_sdk_common/
tracing_timer.rs
