Struct qt::Level

pub struct Level(/* private fields */);
Expand description

Describes the level of verbosity of a span or event.

§Comparing Levels

Level implements the PartialOrd and Ord traits, allowing two Levels to be compared to determine which is considered more or less verbose. Levels which are more verbose are considered “greater than” levels which are less verbose, with Level::ERROR considered the lowest, and Level::TRACE considered the highest.

For example:

use tracing_core::Level;

assert!(Level::TRACE > Level::DEBUG);
assert!(Level::ERROR < Level::WARN);
assert!(Level::INFO <= Level::DEBUG);
assert_eq!(Level::TRACE, Level::TRACE);

§Filtering

Levels are typically used to implement filtering that determines which spans and events are enabled. Depending on the use case, more or less verbose diagnostics may be desired. For example, when running in development, DEBUG-level traces may be enabled by default. When running in production, only INFO-level and lower traces might be enabled. Libraries may include very verbose diagnostics at the DEBUG and/or TRACE levels. Applications using those libraries typically chose to ignore those traces. However, when debugging an issue involving said libraries, it may be useful to temporarily enable the more verbose traces.

The [LevelFilter] type is provided to enable filtering traces by verbosity. Levels can be compared against [LevelFilter]s, and [LevelFilter] has a variant for each Level, which compares analogously to that level. In addition, [LevelFilter] adds a [LevelFilter::OFF] variant, which is considered “less verbose” than every other Level. This is intended to allow filters to completely disable tracing in a particular context.

For example:

use tracing_core::{Level, LevelFilter};

assert!(LevelFilter::OFF < Level::TRACE);
assert!(LevelFilter::TRACE > Level::DEBUG);
assert!(LevelFilter::ERROR < Level::WARN);
assert!(LevelFilter::INFO <= Level::DEBUG);
assert!(LevelFilter::INFO >= Level::INFO);

§Examples

Below is a simple example of how a Subscriber could implement filtering through a [LevelFilter]. When a span or event is recorded, the Subscriber::enabled method compares the span or event’s Level against the configured [LevelFilter]. The optional Subscriber::max_level_hint method can also be implemented to allow spans and events above a maximum verbosity level to be skipped more efficiently, often improving performance in short-lived programs.

use tracing_core::{span, Event, Level, LevelFilter, Subscriber, Metadata};

#[derive(Debug)]
pub struct MySubscriber {
    /// The most verbose level that this subscriber will enable.
    max_level: LevelFilter,

    // ...
}

impl MySubscriber {
    /// Returns a new `MySubscriber` which will record spans and events up to
    /// `max_level`.
    pub fn with_max_level(max_level: LevelFilter) -> Self {
        Self {
            max_level,
            // ...
        }
    }
}
impl Subscriber for MySubscriber {
    fn enabled(&self, meta: &Metadata<'_>) -> bool {
        // A span or event is enabled if it is at or below the configured
        // maximum level.
        meta.level() <= &self.max_level
    }

    // This optional method returns the most verbose level that this
    // subscriber will enable. Although implementing this method is not
    // *required*, it permits additional optimizations when it is provided,
    // allowing spans and events above the max level to be skipped
    // more efficiently.
    fn max_level_hint(&self) -> Option<LevelFilter> {
        Some(self.max_level)
    }

    // Implement the rest of the subscriber...
    fn new_span(&self, span: &span::Attributes<'_>) -> span::Id {
        // ...
    }
    fn event(&self, event: &Event<'_>) {
        // ...
    }

    // ...
}

It is worth noting that the tracing-subscriber crate provides additional APIs for performing more sophisticated filtering, such as enabling different levels based on which module or crate a span or event is recorded in.

Implementations§

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impl Level

pub const ERROR: Level = _

The “error” level.

Designates very serious errors.

pub const WARN: Level = _

The “warn” level.

Designates hazardous situations.

pub const INFO: Level = _

The “info” level.

Designates useful information.

pub const DEBUG: Level = _

The “debug” level.

Designates lower priority information.

pub const TRACE: Level = _

The “trace” level.

Designates very low priority, often extremely verbose, information.

pub fn as_str(&self) -> &'static str

Returns the string representation of the Level.

This returns the same string as the fmt::Display implementation.

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impl AsLog for Level

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type Log = Level

The log type that this type can be converted into.
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fn as_log(&self) -> Level

Returns the log equivalent of self.
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impl<'a> AsSerde<'a> for Level

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type Serializable = SerializeLevel<'a>

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fn as_serde(&'a self) -> <Level as AsSerde<'a>>::Serializable

as_serde borrows a tracing value and returns the serialized value.
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impl Clone for Level

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fn clone(&self) -> Level

Returns a copy of the value. Read more
1.0.0 · source§

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl Debug for Level

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl Display for Level

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fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter. Read more
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impl FromStr for Level

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type Err = ParseLevelError

The associated error which can be returned from parsing.
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fn from_str(s: &str) -> Result<Level, ParseLevelError>

Parses a string s to return a value of this type. Read more
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impl Hash for Level

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fn hash<__H>(&self, state: &mut __H)
where __H: Hasher,

Feeds this value into the given Hasher. Read more
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fn hash_slice<H>(data: &[Self], state: &mut H)
where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher. Read more
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impl Ord for Level

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fn cmp(&self, other: &Level) -> Ordering

This method returns an Ordering between self and other. Read more
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fn max(self, other: Self) -> Self
where Self: Sized,

Compares and returns the maximum of two values. Read more
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fn min(self, other: Self) -> Self
where Self: Sized,

Compares and returns the minimum of two values. Read more
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fn clamp(self, min: Self, max: Self) -> Self
where Self: Sized + PartialOrd,

Restrict a value to a certain interval. Read more
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impl PartialEq<LevelFilter> for Level

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fn eq(&self, other: &LevelFilter) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl PartialEq for Level

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fn eq(&self, other: &Level) -> bool

This method tests for self and other values to be equal, and is used by ==.
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fn ne(&self, other: &Rhs) -> bool

This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.
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impl PartialOrd<LevelFilter> for Level

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fn partial_cmp(&self, other: &LevelFilter) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more
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fn lt(&self, other: &LevelFilter) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
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fn le(&self, other: &LevelFilter) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
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fn gt(&self, other: &LevelFilter) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
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fn ge(&self, other: &LevelFilter) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
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impl PartialOrd for Level

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fn partial_cmp(&self, other: &Level) -> Option<Ordering>

This method returns an ordering between self and other values if one exists. Read more
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fn lt(&self, other: &Level) -> bool

This method tests less than (for self and other) and is used by the < operator. Read more
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fn le(&self, other: &Level) -> bool

This method tests less than or equal to (for self and other) and is used by the <= operator. Read more
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fn gt(&self, other: &Level) -> bool

This method tests greater than (for self and other) and is used by the > operator. Read more
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fn ge(&self, other: &Level) -> bool

This method tests greater than or equal to (for self and other) and is used by the >= operator. Read more
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impl Copy for Level

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impl Eq for Level

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impl StructuralPartialEq for Level

Auto Trait Implementations§

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impl RefUnwindSafe for Level

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impl Send for Level

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impl Sync for Level

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impl Unpin for Level

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impl UnwindSafe for Level

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<Q, K> Comparable<K> for Q
where Q: Ord + ?Sized, K: Borrow<Q> + ?Sized,

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fn compare(&self, key: &K) -> Ordering

Compare self to key and return their ordering.
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impl<T> DynClone for T
where T: Clone,

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fn __clone_box(&self, _: Private) -> *mut ()

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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Compare self to key and return true if they are equal.
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Compare self to key and return true if they are equal.
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impl<Q, K> Equivalent<K> for Q
where Q: Eq + ?Sized, K: Borrow<Q> + ?Sized,

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fn equivalent(&self, key: &K) -> bool

Checks if this value is equivalent to the given key. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> FromRef<T> for T
where T: Clone,

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fn from_ref(input: &T) -> T

Converts to this type from a reference to the input type.
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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided [Span], returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

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

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impl<T> IntoEither for T

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fn into_either(self, into_left: bool) -> Either<Self, Self>

Converts self into a Left variant of Either<Self, Self> if into_left is true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
where F: FnOnce(&Self) -> bool,

Converts self into a Left variant of Either<Self, Self> if into_left(&self) returns true. Converts self into a Right variant of Either<Self, Self> otherwise. Read more
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impl<T> IntoRequest<T> for T

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fn into_request(self) -> Request<T>

Wrap the input message T in a tonic::Request
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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T> ToString for T
where T: Display + ?Sized,

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default fn to_string(&self) -> String

Converts the given value to a String. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<V, T> VZip<V> for T
where V: MultiLane<T>,

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fn vzip(self) -> V

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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a [WithDispatch] wrapper. Read more
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fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a [WithDispatch] wrapper. Read more
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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
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impl<T> RuleType for T
where T: Copy + Debug + Eq + Hash + Ord,