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Showing content from https://docs.rs/tracing-subscriber/latest/tracing_subscriber/filter/targets/struct.Targets.html below:

Targets in tracing_subscriber::filter::targets - Rust

pub struct Targets();

A filter that enables or disables spans and events based on their target and level.

Targets are typically equal to the Rust module path of the code where the span or event was recorded, although they may be overridden.

This type can be used for both per-layer filtering (using its Filter implementation) and global filtering (using its Layer implementation).

See the documentation on filtering with layers for details.

A Targets filter consists of one or more target prefixes, paired with LevelFilters. If a span or event’s target begins with one of those prefixes, and its level is at or below the LevelFilter enabled for that prefix, then the span or event will be enabled.

This is similar to the behavior implemented by the env_logger crate in the log ecosystem.

The EnvFilter type also provided by this crate is very similar to Targets, but is capable of a more sophisticated form of filtering where events may also be enabled or disabled based on the span they are recorded in. Targets can be thought of as a lighter-weight form of EnvFilter that can be used instead when this dynamic filtering is not required.

A Targets filter can be constructed by programmatically adding targets and levels to enable:

use tracing_subscriber::{filter, prelude::*};
use tracing_core::Level;

let filter = filter::Targets::new()
    .with_target("my_crate", Level::INFO)
    .with_target("my_crate::interesting_module", Level::DEBUG);

tracing_subscriber::registry()
    .with(tracing_subscriber::fmt::layer())
    .with(filter)
    .init();

LevelFilter::OFF can be used to disable a particular target:

use tracing_subscriber::filter::{Targets, LevelFilter};
use tracing_core::Level;

let filter = Targets::new()
    .with_target("my_crate", Level::INFO)
    .with_target("my_crate::annoying_module", LevelFilter::OFF);

Alternatively, Targets implements std::str::FromStr, allowing it to be parsed from a comma-delimited list of target=level pairs. For example:

use tracing_subscriber::filter;
use tracing_core::Level;

let filter = "my_crate=info,my_crate::interesting_module=trace,other_crate=debug"
    .parse::<filter::Targets>()?;

assert_eq!(
    filter,
    filter::Targets::new()
        .with_target("my_crate", Level::INFO)
        .with_target("my_crate::interesting_module", Level::TRACE)
        .with_target("other_crate", Level::DEBUG)
);

This is particularly useful when the list of enabled targets is configurable by the user at runtime.

The Targets filter can be used as a per-layer filter and as a global filter:

use tracing_subscriber::{
    fmt,
    filter::{Targets, LevelFilter},
    prelude::*,
};
use tracing_core::Level;
use std::{sync::Arc, fs::File};

let stdout_log = fmt::layer().pretty();

let file = File::create("debug_log.json")?;
let debug_log = fmt::layer()
    .with_writer(Arc::new(file))
    .json();

tracing_subscriber::registry()
    .with(stdout_log
        .with_filter(
            Targets::default()
                .with_target("my_crate::cool_module", Level::DEBUG)
                .with_default(Level::INFO)
       )
    )
    .with(debug_log)
    .with(
        Targets::default()
            .with_target("my_crate", Level::TRACE)
            .with_target("other_crate", Level::INFO)
            .with_target("other_crate::annoying_module", LevelFilter::OFF)
            .with_target("third_crate", Level::DEBUG)
    ).init();

Returns a new Targets filter.

This filter will enable no targets. Call with_target or with_targets to add enabled targets, and with_default to change the default level enabled for spans and events that didn’t match any of the provided targets.

Enables spans and events with targets starting with the provided target prefix if they are at or below the provided LevelFilter.

use tracing_subscriber::filter;
use tracing_core::Level;

let filter = filter::Targets::new()
    .with_target("my_crate", Level::INFO)
    .with_target("my_crate::interesting_module", Level::DEBUG);

LevelFilter::OFF can be used to disable a particular target:

use tracing_subscriber::filter::{Targets, LevelFilter};
use tracing_core::Level;

let filter = Targets::new()
    .with_target("my_crate", Level::INFO)
    .with_target("my_crate::interesting_module", LevelFilter::OFF);

Adds targets from an iterator of target-LevelFilter pairs to this filter.

use tracing_subscriber::filter;
use tracing_core::Level;

let filter = filter::Targets::new()
    .with_targets(vec![
        ("my_crate", Level::INFO),
        ("my_crate::some_module", Level::DEBUG),
        ("my_crate::other_module::cool_stuff", Level::TRACE),
        ("other_crate", Level::WARN)
    ]);

LevelFilter::OFF can be used to disable a particular target:

use tracing_subscriber::filter::{Targets, LevelFilter};
use tracing_core::Level;

let filter = Targets::new()
    .with_target("my_crate", Level::INFO)
    .with_target("my_crate::interesting_module", LevelFilter::OFF);

Sets the default level to enable for spans and events whose targets did not match any of the configured prefixes.

By default, this is LevelFilter::OFF. This means that spans and events will only be enabled if they match one of the configured target prefixes. If this is changed to a different LevelFilter, spans and events with targets that did not match any of the configured prefixes will be enabled if their level is at or below the provided level.

Returns the default level for this filter, if one is set.

The default level is used to filter any spans or events with targets that do not match any of the configured set of prefixes.

The default level can be set for a filter either by using with_default or when parsing from a filter string that includes a level without a target (e.g. "trace").

use tracing_subscriber::filter::{LevelFilter, Targets};

let filter = Targets::new().with_default(LevelFilter::INFO);
assert_eq!(filter.default_level(), Some(LevelFilter::INFO));

let filter: Targets = "info".parse().unwrap();
assert_eq!(filter.default_level(), Some(LevelFilter::INFO));

The default level is None if no default is set:

use tracing_subscriber::filter::Targets;

let filter = Targets::new();
assert_eq!(filter.default_level(), None);

let filter: Targets = "my_crate=info".parse().unwrap();
assert_eq!(filter.default_level(), None);

Note that an unset default level (None) behaves like LevelFilter::OFF when the filter is used, but it could also be set explicitly which may be useful to distinguish (such as when merging multiple Targets).

use tracing_subscriber::filter::{LevelFilter, Targets};

let filter = Targets::new().with_default(LevelFilter::OFF);
assert_eq!(filter.default_level(), Some(LevelFilter::OFF));

let filter: Targets = "off".parse().unwrap();
assert_eq!(filter.default_level(), Some(LevelFilter::OFF));

Returns an iterator over the target-LevelFilter pairs in this filter.

The order of iteration is undefined.

use tracing_subscriber::filter::{Targets, LevelFilter};
use tracing_core::Level;

let filter = Targets::new()
    .with_target("my_crate", Level::INFO)
    .with_target("my_crate::interesting_module", Level::DEBUG);

let mut targets: Vec<_> = filter.iter().collect();
targets.sort();

assert_eq!(targets, vec![
    ("my_crate", LevelFilter::INFO),
    ("my_crate::interesting_module", LevelFilter::DEBUG),
]);

Returns whether a target-Level pair would be enabled by this Targets.

This method can be used with module_path! from std as the target in order to emulate the behavior of the tracing::event! and tracing::span! macros.

use tracing_subscriber::filter::{Targets, LevelFilter};
use tracing_core::Level;

let filter = Targets::new()
    .with_target("my_crate", Level::INFO)
    .with_target("my_crate::interesting_module", Level::DEBUG);

assert!(filter.would_enable("my_crate", &Level::INFO));
assert!(!filter.would_enable("my_crate::interesting_module", &Level::TRACE));

Extends a collection with the contents of an iterator.

Extends a collection with exactly one element.

Reserves capacity in a collection for the given number of additional elements.

Called before the filtered [

on_event

on_event` should be called.

Notifies this filter that a new span was constructed with the given

and

.

Notifies this filter that a span with the given

recorded the given

.

Notifies this filter that a span with the given ID was entered.

Notifies this filter that a span with the given ID was exited.

Notifies this filter that a span with the given ID has been closed.

The associated error which can be returned from parsing.

Parses a string

to return a value of this type.

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

The type of the elements being iterated over.

Which kind of iterator are we turning this into?

Notifies this layer that a new span was constructed with the given Attributes and Id.

Notifies this layer that a span with the given Id recorded the given values.

Notifies this layer that a span with the ID span recorded that it follows from the span with the ID follows.

Notifies this layer that an event has occurred.

Notifies this layer that a span with the given ID was entered.

Notifies this layer that the span with the given ID was exited.

Notifies this layer that the span with the given ID has been closed.

Notifies this layer that a span ID has been cloned, and that the subscriber returned a different ID.

Composes this layer around the given

, returning a

struct implementing

.

Tests for self and other values to be equal, and is used by ==.

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

Performs copy-assignment from

to

.

Combines this

with another

s so that spans and events are enabled if and only if

filters return

.

Combines two

s so that spans and events are enabled if

filter returns

.

Inverts

, returning a filter that enables spans and events only if

would

enable them.

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.

Creates owned data from borrowed data, usually by cloning.

Uses borrowed data to replace owned data, usually by cloning.

The type returned in the event of a conversion error.

Performs the conversion.

The type returned in the event of a conversion error.

Performs the conversion.

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