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pub struct FilterFn<F = fn(_: &Metadata<'_>) -> bool> { /* private fields */ }
Expand description

A filter implemented by a closure or function pointer that determines whether a given span or event is enabled, based on its Metadata.

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.

Implementations

Constructs a FilterFn from a function or closure that returns true if a span or event should be enabled, based on its Metadata.

If determining whether a span or event should be enabled also requires information about the current span context, use DynFilterFn instead.

See the documentation on per-layer filtering for details on using Filters.

Examples
use tracing_subscriber::{
    layer::{Layer, SubscriberExt},
    filter::FilterFn,
    util::SubscriberInitExt,
};

let my_filter = FilterFn::new(|metadata| {
    // Only enable spans or events with the target "interesting_things"
    metadata.target() == "interesting_things"
});

let my_layer = tracing_subscriber::fmt::layer();

tracing_subscriber::registry()
    .with(my_layer.with_filter(my_filter))
    .init();

// This event will not be enabled.
tracing::warn!("something important but uninteresting happened!");

// This event will be enabled.
tracing::debug!(target: "interesting_things", "an interesting minor detail...");

Sets the highest verbosity Level the filter function will enable.

The value passed to this method will be returned by this FilterFn’s Filter::max_level_hint method.

If the provided function will not enable all levels, it is recommended to call this method to configure it with the most verbose level it will enable.

Examples
use tracing_subscriber::{
    layer::{Layer, SubscriberExt},
    filter::{filter_fn, LevelFilter},
    util::SubscriberInitExt,
};
use tracing_core::Level;

let my_filter = filter_fn(|metadata| {
    // Only enable spans or events with targets starting with `my_crate`
    // and levels at or below `INFO`.
    metadata.level() <= &Level::INFO && metadata.target().starts_with("my_crate")
})
    // Since the filter closure will only enable the `INFO` level and
    // below, set the max level hint
    .with_max_level_hint(LevelFilter::INFO);

let my_layer = tracing_subscriber::fmt::layer();

tracing_subscriber::registry()
    .with(my_layer.with_filter(my_filter))
    .init();

Trait Implementations

Returns a copy of the value. Read more

Performs copy-assignment from source. Read more

Formats the value using the given formatter. Read more

Returns true if this layer is interested in a span or event with the given Metadata in the current Context, similarly to Subscriber::enabled. Read more

Returns an Interest indicating whether this layer will always, sometimes, or never be interested in the given Metadata. Read more

Returns an optional hint of the highest verbosity level that this Filter will enable. Read more

Notifies this filter that a new span was constructed with the given Attributes and Id. Read more

Notifies this filter that a span with the given Id recorded the given values. Read more

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

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

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

Performs the conversion.

Returns true if this layer is interested in a span or event with the given metadata in the current Context, similarly to Subscriber::enabled. Read more

Registers a new callsite with this layer, returning whether or not the layer is interested in being notified about the callsite, similarly to Subscriber::register_callsite. Read more

Performs late initialization when attaching a Layer to a Subscriber. Read more

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

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

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

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. Read more

Composes this layer around the given Layer, returning a Layered struct implementing Layer. Read more

Composes this Layer with the given Subscriber, returning a Layered struct that implements Subscriber. Read more

Combines self with a Filter, returning a Filtered layer. Read more

Erases the type of this Layer, returning a Boxed dyn Layer trait object. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more

Immutably borrows from an owned value. Read more

Mutably borrows from an owned value. Read more

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. Read more

🔬 This is a nightly-only experimental API. (toowned_clone_into #41263)

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

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.