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//! log4rs is a highly configurable logging framework modeled after Java's
//! Logback and log4j libraries.
//!
//! # Architecture
//!
//! The basic units of configuration are *appenders*, *encoders*, *filters*, and
//! *loggers*.
//!
//! ## Appenders
//!
//! An appender takes a log record and logs it somewhere, for example, to a
//! file, the console, or the syslog.
//!
//! Implementations:
//! - [console](append/console/struct.ConsoleAppenderDeserializer.html#configuration): requires the `console_appender` feature.
//! - [file](append/file/struct.FileAppenderDeserializer.html#configuration): requires the `file_appender` feature.
//! - [rolling_file](append/rolling_file/struct.RollingFileAppenderDeserializer.html#configuration): requires the `rolling_file_appender` feature and can be configured with the `compound_policy`.
//! - [compound](append/rolling_file/policy/compound/struct.CompoundPolicyDeserializer.html#configuration): requires the `compound_policy` feature
//! - Rollers
//! - [delete](append/rolling_file/policy/compound/roll/delete/struct.DeleteRollerDeserializer.html#configuration): requires the `delete_roller` feature
//! - [fixed_window](append/rolling_file/policy/compound/roll/fixed_window/struct.FixedWindowRollerDeserializer.html#configuration): requires the `fixed_window_roller` feature
//! - Triggers
//! - [size](append/rolling_file/policy/compound/trigger/size/struct.SizeTriggerDeserializer.html#configuration): requires the `size_trigger` feature
//! - [time](append/rolling_file/policy/compound/trigger/tine/struct.TimeTriggerDeserializer.html#configuration): requires the `time_trigger` feature
//!
//! ## Encoders
//!
//! An encoder is responsible for taking a log record, transforming it into the
//! appropriate output format, and writing it out. An appender will normally
//! use an encoder internally.
//!
//! Implementations:
//! - [pattern](encode/pattern/struct.PatternEncoderDeserializer.html#configuration): requires the `pattern_encoder` feature
//! - [json](encode/json/struct.JsonEncoderDeserializer.html#configuration): requires the `json_encoder` feature
//!
//! ## Filters
//!
//! Filters are associated with appenders and, like the name would suggest,
//! filter log events coming into that appender.
//!
//! Implementations:
//! - [threshold](filter/threshold/struct.ThresholdFilterDeserializer.html#configuration): requires the `threshold_filter` feature
//!
//! ## Loggers
//!
//! A log event is targeted at a specific logger, which are identified by
//! string names. The logging macros built in to the `log` crate set the logger
//! of a log event to the one identified by the module containing the
//! invocation location.
//!
//! Loggers form a hierarchy: logger names are divided into components by "::".
//! One logger is the ancestor of another if the first logger's component list
//! is a prefix of the second logger's component list.
//!
//! Loggers are associated with a maximum log level. Log events for that logger
//! with a level above the maximum will be ignored. The maximum log level for
//! any logger can be configured manually; if it is not, the level will be
//! inherited from the logger's parent.
//!
//! Loggers are also associated with a set of appenders. Appenders can be
//! associated directly with a logger. In addition, the appenders of the
//! logger's parent will be associated with the logger unless the logger has
//! its *additive* set to `false`. Log events sent to the logger that are not
//! filtered out by the logger's maximum log level will be sent to all
//! associated appenders.
//!
//! The "root" logger is the ancestor of all other loggers. Since it has no
//! ancestors, its additivity cannot be configured.
//!
//! # Configuration
//!
//! For a detailed breakdown on configuration, refer to the
//! [config module](config/index.html#configuration).
//!
//! log4rs makes heavy use of Cargo features to enable consumers to pick the
//! functionality they wish to use. File-based configuration requires the `file`
//! feature, and each file format requires its own feature as well. In addition,
//! each component has its own feature. For example, YAML support requires the
//! `yaml_format` feature and the console appender requires the
//! `console_appender` feature.
//!
//! By default, the `all_components`, `gzip`, `file`, and `yaml_format` features
//! are enabled.
//!
//! As a convenience, the `all_components` feature activates all logger components.
//!
//! # Examples
//!
//! ## Configuration via a YAML file
//!
//! ```yaml
//! # Scan this file for changes every 30 seconds
//! refresh_rate: 30 seconds
//!
//! appenders:
//! # An appender named "stdout" that writes to stdout
//! stdout:
//! kind: console
//!
//! # An appender named "requests" that writes to a file with a custom pattern encoder
//! requests:
//! kind: file
//! path: "log/requests.log"
//! encoder:
//! pattern: "{d} - {m}{n}"
//!
//! # Set the default logging level to "warn" and attach the "stdout" appender to the root
//! root:
//! level: warn
//! appenders:
//! - stdout
//!
//! loggers:
//! # Raise the maximum log level for events sent to the "app::backend::db" logger to "info"
//! app::backend::db:
//! level: info
//!
//! # Route log events sent to the "app::requests" logger to the "requests" appender,
//! # and *not* the normal appenders installed at the root
//! app::requests:
//! level: info
//! appenders:
//! - requests
//! additive: false
//! ```
//!
//! Add the following in your application initialization.
//!
//! ```no_run
//! # #[cfg(feature = "config_parsing")]
//! # fn f() {
//! log4rs::init_file("log4rs.yml", Default::default()).unwrap();
//! # }
//! ```
//!
//! ## Programmatically constructing a configuration:
//!
//! ```no_run
//! # #[cfg(all(feature = "console_appender",
//! # feature = "file_appender",
//! # feature = "pattern_encoder"))]
//! # fn f() {
//! use log::LevelFilter;
//! use log4rs::append::console::ConsoleAppender;
//! use log4rs::append::file::FileAppender;
//! use log4rs::encode::pattern::PatternEncoder;
//! use log4rs::config::{Appender, Config, Logger, Root};
//!
//! fn main() {
//! let stdout = ConsoleAppender::builder().build();
//!
//! let requests = FileAppender::builder()
//! .encoder(Box::new(PatternEncoder::new("{d} - {m}{n}")))
//! .build("log/requests.log")
//! .unwrap();
//!
//! let config = Config::builder()
//! .appender(Appender::builder().build("stdout", Box::new(stdout)))
//! .appender(Appender::builder().build("requests", Box::new(requests)))
//! .logger(Logger::builder().build("app::backend::db", LevelFilter::Info))
//! .logger(Logger::builder()
//! .appender("requests")
//! .additive(false)
//! .build("app::requests", LevelFilter::Info))
//! .build(Root::builder().appender("stdout").build(LevelFilter::Warn))
//! .unwrap();
//!
//! let handle = log4rs::init_config(config).unwrap();
//!
//! // use handle to change logger configuration at runtime
//! }
//! # }
//! # fn main() {}
//! ```
//!
//! For more examples see the [examples](https://github.com/estk/log4rs/tree/main/examples).
//!
#![allow(where_clauses_object_safety, clippy::manual_non_exhaustive)]
#![warn(missing_docs)]
use std::{
cmp, collections::HashMap, fmt, hash::BuildHasherDefault, io, io::prelude::*, sync::Arc,
};
use arc_swap::ArcSwap;
use fnv::FnvHasher;
use log::{Level, LevelFilter, Metadata, Record};
pub mod append;
pub mod config;
pub mod encode;
pub mod filter;
#[cfg(feature = "console_writer")]
mod priv_io;
pub use config::{init_config, Config};
#[cfg(feature = "config_parsing")]
pub use config::{init_file, init_raw_config};
use self::{append::Append, filter::Filter};
type FnvHashMap<K, V> = HashMap<K, V, BuildHasherDefault<FnvHasher>>;
#[derive(Debug)]
struct ConfiguredLogger {
level: LevelFilter,
appenders: Vec<usize>,
children: FnvHashMap<String, ConfiguredLogger>,
}
impl ConfiguredLogger {
fn add(&mut self, path: &str, mut appenders: Vec<usize>, additive: bool, level: LevelFilter) {
let (part, rest) = match path.find("::") {
Some(idx) => (&path[..idx], &path[idx + 2..]),
None => (path, ""),
};
if let Some(child) = self.children.get_mut(part) {
child.add(rest, appenders, additive, level);
return;
}
let child = if rest.is_empty() {
if additive {
appenders.extend(self.appenders.iter().cloned());
}
ConfiguredLogger {
level,
appenders,
children: FnvHashMap::default(),
}
} else {
let mut child = ConfiguredLogger {
level: self.level,
appenders: self.appenders.clone(),
children: FnvHashMap::default(),
};
child.add(rest, appenders, additive, level);
child
};
self.children.insert(part.to_owned(), child);
}
fn max_log_level(&self) -> LevelFilter {
let mut max = self.level;
for child in self.children.values() {
max = cmp::max(max, child.max_log_level());
}
max
}
fn find(&self, path: &str) -> &ConfiguredLogger {
let mut node = self;
for part in path.split("::") {
match node.children.get(part) {
Some(child) => node = child,
None => break,
}
}
node
}
fn enabled(&self, level: Level) -> bool {
self.level >= level
}
fn log(&self, record: &log::Record, appenders: &[Appender]) -> Result<(), Vec<anyhow::Error>> {
let mut errors = vec![];
if self.enabled(record.level()) {
for &idx in &self.appenders {
if let Err(err) = appenders[idx].append(record) {
errors.push(err);
}
}
}
if errors.is_empty() {
Ok(())
} else {
Err(errors)
}
}
}
#[derive(Debug)]
struct Appender {
appender: Box<dyn Append>,
filters: Vec<Box<dyn Filter>>,
}
impl Appender {
fn append(&self, record: &Record) -> anyhow::Result<()> {
for filter in &self.filters {
match filter.filter(record) {
filter::Response::Accept => break,
filter::Response::Neutral => {}
filter::Response::Reject => return Ok(()),
}
}
self.appender.append(record)
}
fn flush(&self) {
self.appender.flush();
}
}
struct SharedLogger {
root: ConfiguredLogger,
appenders: Vec<Appender>,
err_handler: Box<dyn Send + Sync + Fn(&anyhow::Error)>,
}
impl fmt::Debug for SharedLogger {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_struct("SharedLogger")
.field("root", &self.root)
.field("appenders", &self.appenders)
.finish()
}
}
impl SharedLogger {
fn new(config: config::Config) -> SharedLogger {
Self::new_with_err_handler(
config,
Box::new(|e: &anyhow::Error| {
let _ = writeln!(io::stderr(), "log4rs: {}", e);
}),
)
}
fn new_with_err_handler(
config: config::Config,
err_handler: Box<dyn Send + Sync + Fn(&anyhow::Error)>,
) -> SharedLogger {
let (appenders, root, mut loggers) = config.unpack();
let root = {
let appender_map = appenders
.iter()
.enumerate()
.map(|(i, appender)| (appender.name(), i))
.collect::<HashMap<_, _>>();
let mut root = ConfiguredLogger {
level: root.level(),
appenders: root
.appenders()
.iter()
.map(|appender| appender_map[&**appender])
.collect(),
children: FnvHashMap::default(),
};
// sort loggers by name length to ensure that we initialize them top to bottom
loggers.sort_by_key(|l| l.name().len());
for logger in loggers {
let appenders = logger
.appenders()
.iter()
.map(|appender| appender_map[&**appender])
.collect();
root.add(logger.name(), appenders, logger.additive(), logger.level());
}
root
};
let appenders = appenders
.into_iter()
.map(|appender| {
let (_, appender, filters) = appender.unpack();
Appender { appender, filters }
})
.collect();
SharedLogger {
root,
appenders,
err_handler,
}
}
}
/// The fully configured log4rs Logger which is appropriate
/// to use with the `log::set_boxed_logger` function.
#[derive(Debug)]
pub struct Logger(Arc<ArcSwap<SharedLogger>>);
impl Logger {
/// Create a new `Logger` given a configuration.
pub fn new(config: config::Config) -> Logger {
Logger(Arc::new(ArcSwap::new(Arc::new(SharedLogger::new(config)))))
}
/// Create a new `Logger` given a configuration and err handler.
pub fn new_with_err_handler(
config: config::Config,
err_handler: Box<dyn Send + Sync + Fn(&anyhow::Error)>,
) -> Logger {
Logger(Arc::new(ArcSwap::new(Arc::new(
SharedLogger::new_with_err_handler(config, err_handler),
))))
}
/// Set the max log level above which everything will be filtered.
pub fn max_log_level(&self) -> LevelFilter {
self.0.load().root.max_log_level()
}
}
impl log::Log for Logger {
fn enabled(&self, metadata: &Metadata) -> bool {
self.0
.load()
.root
.find(metadata.target())
.enabled(metadata.level())
}
fn log(&self, record: &log::Record) {
let shared = self.0.load();
if let Err(errs) = shared
.root
.find(record.target())
.log(record, &shared.appenders)
{
for e in errs {
(shared.err_handler)(&e)
}
}
}
fn flush(&self) {
for appender in &self.0.load().appenders {
appender.flush();
}
}
}
pub(crate) fn handle_error(e: &anyhow::Error) {
let _ = writeln!(io::stderr(), "log4rs: {}", e);
}
/// A handle to the active logger.
#[derive(Clone, Debug)]
pub struct Handle {
shared: Arc<ArcSwap<SharedLogger>>,
}
impl Handle {
/// Sets the logging configuration.
pub fn set_config(&self, config: Config) {
let shared = SharedLogger::new(config);
log::set_max_level(shared.root.max_log_level());
self.shared.store(Arc::new(shared));
}
}
#[cfg(test)]
mod test {
use log::{Level, LevelFilter, Log};
use super::*;
#[test]
#[cfg(all(feature = "config_parsing", feature = "json_format"))]
fn init_from_raw_config() {
let dir = tempfile::tempdir().unwrap();
let path = dir.path().join("append.log");
let cfg = serde_json::json!({
"refresh_rate": "60 seconds",
"root" : {
"appenders": ["baz"],
"level": "info",
},
"appenders": {
"baz": {
"kind": "file",
"path": path,
"encoder": {
"pattern": "{m}"
}
}
},
});
let config = serde_json::from_str::<config::RawConfig>(&cfg.to_string()).unwrap();
if let Err(e) = init_raw_config(config) {
panic!("{}", e);
}
assert!(path.exists());
log::info!("init_from_raw_config");
let mut contents = String::new();
std::fs::File::open(&path)
.unwrap()
.read_to_string(&mut contents)
.unwrap();
assert_eq!(contents, "init_from_raw_config");
}
#[test]
fn enabled() {
let root = config::Root::builder().build(LevelFilter::Debug);
let mut config = config::Config::builder();
let logger = config::Logger::builder().build("foo::bar", LevelFilter::Trace);
config = config.logger(logger);
let logger = config::Logger::builder().build("foo::bar::baz", LevelFilter::Off);
config = config.logger(logger);
let logger = config::Logger::builder().build("foo::baz::buz", LevelFilter::Error);
config = config.logger(logger);
let config = config.build(root).unwrap();
let logger = super::Logger::new(config);
assert!(logger.enabled(&Metadata::builder().level(Level::Warn).target("bar").build()));
assert!(!logger.enabled(
&Metadata::builder()
.level(Level::Trace)
.target("bar")
.build()
));
assert!(logger.enabled(
&Metadata::builder()
.level(Level::Debug)
.target("foo")
.build()
));
assert!(logger.enabled(
&Metadata::builder()
.level(Level::Trace)
.target("foo::bar")
.build()
));
assert!(!logger.enabled(
&Metadata::builder()
.level(Level::Error)
.target("foo::bar::baz")
.build()
));
assert!(logger.enabled(
&Metadata::builder()
.level(Level::Debug)
.target("foo::bar::bazbuz")
.build()
));
assert!(!logger.enabled(
&Metadata::builder()
.level(Level::Error)
.target("foo::bar::baz::buz")
.build()
));
assert!(!logger.enabled(
&Metadata::builder()
.level(Level::Warn)
.target("foo::baz::buz")
.build()
));
assert!(!logger.enabled(
&Metadata::builder()
.level(Level::Warn)
.target("foo::baz::buz::bar")
.build()
));
assert!(logger.enabled(
&Metadata::builder()
.level(Level::Error)
.target("foo::baz::buz::bar")
.build()
));
}
}