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## Motivation Several currently open PRs, such as #2225 and #2221, add new configuration parameters to the rolling file appender in `tracing-appender`. The best way to add new optional configuration settings without breaking existing APIs or creating a very large number of new constructors is to add a builder interface. ## Solution Since a number of PRs would all need to add the builder API, introducing potential conflicts, this branch _just_ adds the builder interface without adding any new configuration options. Once this merges, the existing in-flight PRs can be rebased onto this branch to use the builder interface without conflicting with each other. Also, the `Builder::build` method is fallible and returns a `Result`, rather than panicking. This is a relatively common pattern in Rust --- for example, `std:🧵:Builder::spawn` returns a `Result` if a new thread cannot be spawned, while `std:🧵:spawn` simply panics. This allows users to handle appender initialization errors gracefully without breaking the API of the existing `new` constructor. Fixes #1953 Signed-off-by: Eliza Weisman <eliza@buoyant.io>
tracing-appender
Writers for logging events and spans
Overview
tracing is a framework for instrumenting Rust programs to
collect structured, event-based diagnostic information. tracing-appender
allows events and spans to be recorded in a non-blocking manner through a
dedicated logging thread. It also provides a RollingFileAppender
that can be used with or without the non-blocking writer.
Compiler support: requires rustc 1.53+
Usage
Add the following to your Cargo.toml:
tracing-appender = "0.2"
This crate can be used in a few ways to record spans/events:
- Using a
RollingFileAppenderto write to a log file. This is a blocking operation. - Using any type implementing
std::io::Writein a non-blocking fashion. - Using
NonBlockingandRollingFileAppendertogether to write to log files in a non-blocking fashion.
Rolling File Appender
fn main(){
let file_appender = tracing_appender::rolling::hourly("/some/directory", "prefix.log");
}
This creates an hourly rotating file appender that writes to
/some/directory/prefix.log.YYYY-MM-DD-HH. [Rotation::DAILY] and
[Rotation::NEVER] are the other available options.
The file appender implements std::io::Write. To be used with
tracing_subscriber::FmtSubscriber, it must be combined
with a MakeWriter implementation to be able to record
tracing spans/event.
The rolling module's documentation provides more detail on how to use this file appender.
Non-Blocking Writer
The example below demonstrates the construction of a non_blocking writer
with an implementation of std::io::Writer.
use std::io::Error;
struct TestWriter;
impl std::io::Write for TestWriter {
fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
let buf_len = buf.len();
println!("{:?}", buf);
Ok(buf_len)
}
fn flush(&mut self) -> std::io::Result<()> {
Ok(())
}
}
fn main() {
let (non_blocking, _guard) = tracing_appender::non_blocking(TestWriter);
tracing_subscriber::fmt().with_writer(non_blocking).init();
}
Note: _guard is a WorkerGuard which is returned by
tracing_appender::non_blocking to ensure buffered logs are flushed to
their output in the case of abrupt terminations of a process. See
WorkerGuard module for more details.
The example below demonstrates the construction of a
tracing_appender::non_blocking writer constructed with
a std::io::Write:
fn main() {
let (non_blocking, _guard) = tracing_appender::non_blocking(std::io::stdout());
tracing_subscriber::fmt()
.with_writer(non_blocking)
.init();
}
The non_blocking module's documentation provides more detail on how to
use non_blocking.
Non-Blocking Rolling File Appender
fn main() {
let file_appender = tracing_appender::rolling::hourly("/some/directory", "prefix.log");
let (non_blocking, _guard) = tracing_appender::non_blocking(file_appender);
tracing_subscriber::fmt()
.with_writer(non_blocking)
.init();
}
Supported Rust Versions
tracing-appender is built against the latest stable release. The minimum supported
version is 1.53. The current tracing-appender version is not guaranteed to build on
Rust versions earlier than the minimum supported version.
Tracing follows the same compiler support policies as the rest of the Tokio project. The current stable Rust compiler and the three most recent minor versions before it will always be supported. For example, if the current stable compiler version is 1.45, the minimum supported version will not be increased past 1.42, three minor versions prior. Increasing the minimum supported compiler version is not considered a semver breaking change as long as doing so complies with this policy.
License
This project is licensed under the MIT license.
Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in Tokio by you, shall be licensed as MIT, without any additional terms or conditions.