Logging is affected by the disk IO and pipe system call. Sequential log calls can be a bottleneck in scenarios where low latency is critical (e.g., high-frequency trading).
ftlog mitigates this bottleneck by sending messages to a dedicated logger
thread and computing as little as possible in the main/worker thread.
ftlog can improve log performance in main/worker thread a few times over. See
performance for details.
Add to your Cargo.toml:
toml
ftlog = "0.2"
Configure and initialize ftlog at the start of your main function:
``rust
// ftlog re-exportlog's macros, so no need to addlog` to dependencies
use ftlog::appender::FileAppender;
use ftlog::{debug, trace};
use log::{error, info, warn};
// minimal configuration with default setting ftlog::builder().try_init().unwrap();
trace!("Hello world!"); debug!("Hello world!"); info!("Hello world!"); warn!("Hello world!"); error!("Hello world!");
// When main thread is done, ftlog worker thread may be busy printing messages. // Manually flush log output, otherwise messages in memory yet might lost log::logger().flush(); ```
A more complicated but feature rich usage:
```rust use ftlog::{ appender::{Duration, FileAppender, Period}, FtLogFormatter, LevelFilter, };
let timeformat = time::formatdescription::parseowned::<1>(
"[year]-[month]-[day] [hour]:[minute]:[second].[subsecond digits:6]",
)
.unwrap();
// configurate logger
let logger = ftlog::builder()
// global max log level
.maxloglevel(LevelFilter::Info)
// custom timestamp format
.timeformat(timeformat)
// set global log formatter
.format(FtLogFormatter)
// use bounded channel to avoid large memory comsumption when overwhelmed with logs
// Set false to tell ftlog to discard excessive logs.
// Set true to block log call to wait for log thread.
// here is the default settings
.bounded(100000, false) // .unbounded()
// define root appender, pass anything that is Write and Send
// omit Builder::root will write to stderr
.root(FileAppender::rotatewithexpire(
"./current.log",
Period::Day,
Duration::days(7),
))
// Do not convert to local timezone for timestamp, this does not affect worker thread,
// but can boost log thread performance (higher throughput).
.utc()
// level filter for root appender
.rootloglevel(LevelFilter::Warn)
// write logs in ftlog::appender to "./ftlog-appender.log" instead of "./current.log"
.filter("ftlog::appender", "ftlog-appender", LevelFilter::Error)
.appender("ftlog-appender", FileAppender::new("ftlog-appender.log"))
.try_init()
.expect("logger build or set failed");
```
See ./examples for more (e.g. custom format).
2022-04-08 19:20:48.190+08 298ms INFO main [src/ftlog.rs:14] My log message
Here 298ms denotes the latency between the call of the log (e.g.
log::info!("msg")) and the actual printing in log thread. Normally this is 0ms.
A large delay indicates that the log thread may be blocked by excessive log messages.
2022-04-10 21:27:15.996+08 0ms 2 INFO main [src/main.rs:29] limit running3 !
The number 2 above indicates how many log messages were discarded.
Only shown if the frequency of logging for a single log call is limited (e.g.
log::info!(limit=3000i64;"msg")).
ftlog relies on the time crate for the formatting of timestamp. To use custom time format,
first construct a valid time format description,
and then pass it to ftlog builder by ftlog::time_format(&mut self).
In case an error occurs when formatting timestamp, ftlog will fallback to RFC3339 time format.
rust
let format = time::format_description::parse_owned::<1>(
"[year]/[month]/[day] [hour]:[minute]:[second].[subsecond digits:6]",
)
.unwrap();
ftlog::builder().time_format(format).try_init().unwrap();
log::info!("Log with custom timestamp format");
// Output:
// 2023/06/14 11:13:26.160840 0ms INFO main [main.rs:3] Log with custom timestamp format
ftlog allows to limit the write frequency for individual log calls.
If the above line is called multiple times within 3000ms, then it is logged only once, with an added number reflecting the number of discarded log messages.
Each log call ha an independent interval, so we can set different intervals
for different log calls. Internally, ftlog records the last print time by a
combination of (module name, file name, code line).
rust
info!(limit=3000i64; "limit running {}s !", 3);
The minimal interval of the the specific log call above is 3000ms.
markdown
2022-04-10 21:27:10.996+08 0ms 0 INFO main [src/main.rs:29] limit running 3s !
2022-04-10 21:27:15.996+08 0ms 2 INFO main [src/main.rs:29] limit running 3s !
The number 2 above shows how many log messages is discarded since last log.
ftlog supports log rotation in local timezone. The available rotation
periods are:
Period::MinutePeriod::HourPeriod::DayPeriod::MonthPeriod::YearLog rotation is configured in FileAppender, and the timestamp is appended to
the end of the filename:
```rust use ftlog::appender::{FileAppender, Period};
let logger = ftlog::builder() .root(FileAppender::rotate("./mylog.log", Period::Minute)) .build() .unwrap(); logger.init().unwrap(); ```
If the log file is configued to be split by minutes,
the log file name has the format
mylog-{MMMM}{YY}{DD}T{hh}{mm}.log. When divided by days, the log file name is
something like mylog-{MMMM}{YY}{DD}.log.
Log filename examples: ```sh $ ls
current-20221026T1351.log
current-20221026T13.log
current-20221026.log
current-202210.log
current-2022.log
log-20221026T1351 ```
With log rotation enabled, it is possible to clean outdated logs to free up
disk space with FileAppender::rotate_with_expire method.
ftlog first finds files generated by ftlog and cleans outdated logs by
last modified time. ftlog find generated logs by filename matched by file
stem and added datetime.
ATTENTION: Any files that matchs the pattern will be deleted.
```rust use ftlog::{appender::{Period, FileAppender, Duration}};
// clean files named like current-\d{8}T\d{4}.log.
// files like another-\d{8}T\d{4}.log or current-\d{8}T\d{4} will not be deleted, since the filenames' stem do not match.
// files like current-\d{8}.log will remains either, since the rotation durations do not match.
// Rotate every day, clean stale logs that were modified 7 days ago on each rotation let appender = FileAppender::rotatewithexpire("./current.log", Period::Day, Duration::days(7)); let logger = ftlog::builder() .root(appender) .build() .unwrap(); logger.init().unwrap(); ```
tsc Use TSC for clock source for higher performance without accuracy loss.
TSC offers the most accurate and cheapest way to access current time under certain condition:
The current feature further requires that the build target MUST BE LINUX. Otherwise it will fall back to a fast but much less accurate implementation.
For performance, timezone is detected once at logger buildup, and use it later in every log message. This is partly due to timezone detetion is expensive, and partly to the unsafe nature of underlying system call in multi-thread program in Linux.
It's also recommended to use UTC instead to further avoid timestamp convertion to timezone for every log message.
Rust：1.67.0-nightly
| | message type | Apple M1 Pro, 3.2GHz | AMD EPYC 7T83, 3.2GHz |
| ------------------------------------------------- | ------------- | --------------------- | --------------------- |
| ftlog | static string | 75 ns/iter | 385 ns/iter |
| ftlog | with i32 | 106 ns/iter | 491 ns/iter |
| env_logger
output to file | static string | 1,674 ns/iter | 1,142 ns/iter |
| env_logger
output to file | with i32 | 1,681 ns/iter | 1,179 ns/iter |
| env_logger
output to file with BufWriter| static string | 279 ns/iter | 550 ns/iter |
| env_logger
output to file with BufWriter| with i32 | 278 ns/iter | 565 ns/iter |
License: MIT OR Apache-2.0