Module flexi_logger::trc[−][src]

This is supported on crate feature trc only.

Expand description

Use `flexi_logger` functionality with `tracing`.

tracing is an alternative to log. It has a similar base architecture, but is optimized for supporting async apps, which adds complexity due to the need to manage contexts. tracing-subscriber facilitates contributing “backends”, and is used in the example below to plug flexi_logger-functionality into tracing.

The content of this module is a first attempt to support such an integration. Every feedback is highly appreciated.

Example

The following example uses a FileLogWriter as trace writer, and flexi_logger’s specfile handling to adapt tracing dynamically, while your program is running. The code is a bit cumbersome, maybe there are (oor will be) easier ways to achieve the same.

Precondition: add these entries to your Cargo.toml:

flexi_logger = {version = "0.19", features = ["trc"]}
tracing = "0.1"
tracing-subscriber = {version = "0.2.20", features = ["env-filter"]}

use flexi_logger::{
    trc::{subscribe_to_specfile, BasicLogSpecSubscriber, LogSpecAsFilter},
    writers::FileLogWriter,
    Age, Cleanup, Criterion, FileSpec, LogSpecification, Naming, WriteMode,
};

use tracing::{debug, info, trace, warn};
use tracing_subscriber::FmtSubscriber;

// Prepare a `FileLogWriter` and a handle to it, and keep the handle alive
// until the program ends (it will flush and shutdown the `FileLogWriter` when dropped).
// For the `FileLogWriter`, use the settings that fit your needs
let (file_writer, _fw_handle) = FileLogWriter::builder(FileSpec::default())
    .rotate(
        // If the program runs long enough,
        Criterion::Age(Age::Day), // - create a new file every day
        Naming::Timestamps,       // - let the rotated files have a timestamp in their name
        Cleanup::KeepLogFiles(7), // - keep at most seven log files
    )
    .write_mode(WriteMode::Async)
    .try_build_with_handle()
    .unwrap();

// Set up subscriber that makes use of the file writer, with some hardcoded initial log spec
let initial_logspec = LogSpecification::info();
let subscriber_builder = FmtSubscriber::builder()
    .with_writer(move || file_writer.clone())
    .with_env_filter(LogSpecAsFilter(initial_logspec.clone()))
    .with_filter_reloading();

// Set up specfile tracking and subscribe
let reload_handle = Box::new(subscriber_builder.reload_handle());
subscribe_to_specfile(
    "trcspecfile.toml",
    BasicLogSpecSubscriber::new(
        Box::new(move |logspec| reload_handle.reload(LogSpecAsFilter(logspec)).unwrap()),
        initial_logspec,
    ),
)
.unwrap();

// Get ready to trace
tracing::subscriber::set_global_default(subscriber_builder.finish())
    .expect("setting default subscriber failed");

// now do what you really want to do...

Structs

BasicLogSpecSubscriber

Helper struct that can be registered in subscribe_to_specfile to get informed about updates to the specfile, and can be registered in tracing to forward such updates.

LogSpecAsFilter

Helper struct for using LogSpecification as filter in tracing.

Traits

LogSpecSubscriber

Trait that allows to register for changes to the log specification.

Functions

subscribe_to_specfile