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use super::{RollingFileAppender, Rotation};
use std::{io, path::Path};
use thiserror::Error;
/// A [builder] for configuring [`RollingFileAppender`]s.
///
/// [builder]: https://rust-unofficial.github.io/patterns/patterns/creational/builder.html
#[derive(Debug)]
pub struct Builder {
pub(super) rotation: Rotation,
pub(super) prefix: Option<String>,
pub(super) suffix: Option<String>,
pub(super) max_files: Option<usize>,
}
/// Errors returned by [`Builder::build`].
#[derive(Error, Debug)]
#[error("{context}: {source}")]
pub struct InitError {
context: &'static str,
#[source]
source: io::Error,
}
impl InitError {
pub(crate) fn ctx(context: &'static str) -> impl FnOnce(io::Error) -> Self {
move |source| Self { context, source }
}
}
impl Builder {
/// Returns a new `Builder` for configuring a [`RollingFileAppender`], with
/// the default parameters.
///
/// # Default Values
///
/// The default values for the builder are:
///
/// | Parameter | Default Value | Notes |
/// | :-------- | :------------ | :---- |
/// | [`rotation`] | [`Rotation::NEVER`] | By default, log files will never be rotated. |
/// | [`filename_prefix`] | `""` | By default, log file names will not have a prefix. |
/// | [`filename_suffix`] | `""` | By default, log file names will not have a suffix. |
/// | [`max_log_files`] | `None` | By default, there is no limit for maximum log file count. |
///
/// [`rotation`]: Self::rotation
/// [`filename_prefix`]: Self::filename_prefix
/// [`filename_suffix`]: Self::filename_suffix
/// [`max_log_files`]: Self::max_log_files
#[must_use]
pub const fn new() -> Self {
Self {
rotation: Rotation::NEVER,
prefix: None,
suffix: None,
max_files: None,
}
}
/// Sets the [rotation strategy] for log files.
///
/// By default, this is [`Rotation::NEVER`].
///
/// # Examples
///
/// ```
/// # fn docs() {
/// use tracing_appender::rolling::{Rotation, RollingFileAppender};
///
/// let appender = RollingFileAppender::builder()
/// .rotation(Rotation::HOURLY) // rotate log files once every hour
/// // ...
/// .build("/var/log")
/// .expect("failed to initialize rolling file appender");
///
/// # drop(appender)
/// # }
/// ```
///
/// [rotation strategy]: Rotation
#[must_use]
pub fn rotation(self, rotation: Rotation) -> Self {
Self { rotation, ..self }
}
/// Sets the prefix for log filenames. The prefix is output before the
/// timestamp in the file name, and if it is non-empty, it is followed by a
/// dot (`.`).
///
/// By default, log files do not have a prefix.
///
/// # Examples
///
/// Setting a prefix:
///
/// ```
/// use tracing_appender::rolling::RollingFileAppender;
///
/// # fn docs() {
/// let appender = RollingFileAppender::builder()
/// .filename_prefix("myapp.log") // log files will have names like "myapp.log.2019-01-01"
/// // ...
/// .build("/var/log")
/// .expect("failed to initialize rolling file appender");
/// # drop(appender)
/// # }
/// ```
///
/// No prefix:
///
/// ```
/// use tracing_appender::rolling::RollingFileAppender;
///
/// # fn docs() {
/// let appender = RollingFileAppender::builder()
/// .filename_prefix("") // log files will have names like "2019-01-01"
/// // ...
/// .build("/var/log")
/// .expect("failed to initialize rolling file appender");
/// # drop(appender)
/// # }
/// ```
///
/// [rotation strategy]: Rotation
#[must_use]
pub fn filename_prefix(self, prefix: impl Into<String>) -> Self {
let prefix = prefix.into();
// If the configured prefix is the empty string, then don't include a
// separator character.
let prefix = if prefix.is_empty() {
None
} else {
Some(prefix)
};
Self { prefix, ..self }
}
/// Sets the suffix for log filenames. The suffix is output after the
/// timestamp in the file name, and if it is non-empty, it is preceded by a
/// dot (`.`).
///
/// By default, log files do not have a suffix.
///
/// # Examples
///
/// Setting a suffix:
///
/// ```
/// use tracing_appender::rolling::RollingFileAppender;
///
/// # fn docs() {
/// let appender = RollingFileAppender::builder()
/// .filename_suffix("myapp.log") // log files will have names like "2019-01-01.myapp.log"
/// // ...
/// .build("/var/log")
/// .expect("failed to initialize rolling file appender");
/// # drop(appender)
/// # }
/// ```
///
/// No suffix:
///
/// ```
/// use tracing_appender::rolling::RollingFileAppender;
///
/// # fn docs() {
/// let appender = RollingFileAppender::builder()
/// .filename_suffix("") // log files will have names like "2019-01-01"
/// // ...
/// .build("/var/log")
/// .expect("failed to initialize rolling file appender");
/// # drop(appender)
/// # }
/// ```
///
/// [rotation strategy]: Rotation
#[must_use]
pub fn filename_suffix(self, suffix: impl Into<String>) -> Self {
let suffix = suffix.into();
// If the configured suffix is the empty string, then don't include a
// separator character.
let suffix = if suffix.is_empty() {
None
} else {
Some(suffix)
};
Self { suffix, ..self }
}
/// Keeps the last `n` log files on disk.
///
/// When a new log file is created, if there are `n` or more
/// existing log files in the directory, the oldest will be deleted.
/// If no value is supplied, the `RollingAppender` will not remove any files.
///
/// Files are considered candidates for deletion based on the following
/// criteria:
///
/// * The file must not be a directory or symbolic link.
/// * If the appender is configured with a [`filename_prefix`], the file
/// name must start with that prefix.
/// * If the appender is configured with a [`filename_suffix`], the file
/// name must end with that suffix.
/// * If the appender has neither a filename prefix nor a suffix, then the
/// file name must parse as a valid date based on the appender's date
/// format.
///
/// Files matching these criteria may be deleted if the maximum number of
/// log files in the directory has been reached.
///
/// [`filename_prefix`]: Self::filename_prefix
/// [`filename_suffix`]: Self::filename_suffix
///
/// # Examples
///
/// ```
/// use tracing_appender::rolling::RollingFileAppender;
///
/// # fn docs() {
/// let appender = RollingFileAppender::builder()
/// .max_log_files(5) // only the most recent 5 log files will be kept
/// // ...
/// .build("/var/log")
/// .expect("failed to initialize rolling file appender");
/// # drop(appender)
/// # }
/// ```
#[must_use]
pub fn max_log_files(self, n: usize) -> Self {
Self {
max_files: Some(n),
..self
}
}
/// Builds a new [`RollingFileAppender`] with the configured parameters,
/// emitting log files to the provided directory.
///
/// Unlike [`RollingFileAppender::new`], this returns a `Result` rather than
/// panicking when the appender cannot be initialized.
///
/// # Examples
///
/// ```
/// use tracing_appender::rolling::{Rotation, RollingFileAppender};
///
/// # fn docs() {
/// let appender = RollingFileAppender::builder()
/// .rotation(Rotation::DAILY) // rotate log files once per day
/// .filename_prefix("myapp.log") // log files will have names like "myapp.log.2019-01-01"
/// .build("/var/log/myapp") // write log files to the '/var/log/myapp' directory
/// .expect("failed to initialize rolling file appender");
/// # drop(appender);
/// # }
/// ```
///
/// This is equivalent to
/// ```
/// # fn docs() {
/// let appender = tracing_appender::rolling::daily("myapp.log", "/var/log/myapp");
/// # drop(appender);
/// # }
/// ```
pub fn build(&self, directory: impl AsRef<Path>) -> Result<RollingFileAppender, InitError> {
RollingFileAppender::from_builder(self, directory)
}
}
impl Default for Builder {
fn default() -> Self {
Self::new()
}
}