Struct tracing_subscriber::fmt::Layer
source · [−]pub struct Layer<S, N = DefaultFields, E = Format<Full>, W = fn() -> Stdout> { /* private fields */ }
Expand description
A Layer
that logs formatted representations of tracing
events.
Examples
Constructing a layer with the default configuration:
use tracing_subscriber::{fmt, Registry};
use tracing_subscriber::prelude::*;
let subscriber = Registry::default()
.with(fmt::Layer::default());
tracing::subscriber::set_global_default(subscriber).unwrap();
Overriding the layer’s behavior:
use tracing_subscriber::{fmt, Registry};
use tracing_subscriber::prelude::*;
let fmt_layer = fmt::layer()
.with_target(false) // don't include event targets when logging
.with_level(false); // don't include event levels when logging
let subscriber = Registry::default().with(fmt_layer);
Setting a custom event formatter:
use tracing_subscriber::fmt::{self, format, time};
use tracing_subscriber::prelude::*;
let fmt = format().with_timer(time::Uptime::default());
let fmt_layer = fmt::layer()
.event_format(fmt)
.with_target(false);
Implementations
sourceimpl<S, N, E, W> Layer<S, N, E, W> where
S: Subscriber + for<'a> LookupSpan<'a>,
N: for<'writer> FormatFields<'writer> + 'static,
W: for<'writer> MakeWriter<'writer> + 'static,
impl<S, N, E, W> Layer<S, N, E, W> where
S: Subscriber + for<'a> LookupSpan<'a>,
N: for<'writer> FormatFields<'writer> + 'static,
W: for<'writer> MakeWriter<'writer> + 'static,
sourcepub fn event_format<E2>(self, e: E2) -> Layer<S, N, E2, W> where
E2: FormatEvent<S, N> + 'static,
pub fn event_format<E2>(self, e: E2) -> Layer<S, N, E2, W> where
E2: FormatEvent<S, N> + 'static,
Sets the event formatter that the layer being built will use to format events.
The event formatter may be any type implementing the FormatEvent
trait, which is implemented for all functions taking a FmtContext
, a
Writer
, and an Event
.
Examples
Setting a type implementing FormatEvent
as the formatter:
use tracing_subscriber::fmt::{self, format};
let layer = fmt::layer()
.event_format(format().compact());
sourcepub fn map_event_format<E2>(self, f: impl FnOnce(E) -> E2) -> Layer<S, N, E2, W> where
E2: FormatEvent<S, N> + 'static,
pub fn map_event_format<E2>(self, f: impl FnOnce(E) -> E2) -> Layer<S, N, E2, W> where
E2: FormatEvent<S, N> + 'static,
Updates the event formatter by applying a function to the existing event formatter.
This sets the event formatter that the layer being built will use to record fields.
Examples
Updating an event formatter:
let layer = tracing_subscriber::fmt::layer()
.map_event_format(|e| e.compact());
sourceimpl<S, N, E, W> Layer<S, N, E, W>
impl<S, N, E, W> Layer<S, N, E, W>
sourcepub fn with_writer<W2>(self, make_writer: W2) -> Layer<S, N, E, W2> where
W2: for<'writer> MakeWriter<'writer> + 'static,
pub fn with_writer<W2>(self, make_writer: W2) -> Layer<S, N, E, W2> where
W2: for<'writer> MakeWriter<'writer> + 'static,
Sets the MakeWriter
that the layer being built will use to write events.
Examples
Using stderr
rather than stdout
:
use std::io;
use tracing_subscriber::fmt;
let layer = fmt::layer()
.with_writer(io::stderr);
sourcepub fn writer_mut(&mut self) -> &mut W
pub fn writer_mut(&mut self) -> &mut W
Mutably borrows the writer for this Layer
.
This method is primarily expected to be used with the
reload::Handle::modify
method.
Examples
let layer = fmt::layer().with_writer(non_blocking(std::io::stderr()));
let (layer, reload_handle) = reload::Layer::new(layer);
info!("This will be logged to stderr");
reload_handle.modify(|layer| *layer.writer_mut() = non_blocking(std::io::stdout()));
info!("This will be logged to stdout");
sourcepub fn set_ansi(&mut self, ansi: bool)
pub fn set_ansi(&mut self, ansi: bool)
Sets whether this layer should use ANSI terminal formatting escape codes (such as colors).
This method is primarily expected to be used with the
reload::Handle::modify
method when changing
the writer.
sourcepub fn with_test_writer(self) -> Layer<S, N, E, TestWriter>
pub fn with_test_writer(self) -> Layer<S, N, E, TestWriter>
Configures the layer to support libtest
’s output capturing when used in
unit tests.
See TestWriter
for additional details.
Examples
Using TestWriter
to let cargo test
capture test output:
use std::io;
use tracing_subscriber::fmt;
let layer = fmt::layer()
.with_test_writer();
sourcepub fn map_writer<W2>(self, f: impl FnOnce(W) -> W2) -> Layer<S, N, E, W2> where
W2: for<'writer> MakeWriter<'writer> + 'static,
pub fn map_writer<W2>(self, f: impl FnOnce(W) -> W2) -> Layer<S, N, E, W2> where
W2: for<'writer> MakeWriter<'writer> + 'static,
Updates the MakeWriter
by applying a function to the existing MakeWriter
.
This sets the MakeWriter
that the layer being built will use to write events.
Examples
Redirect output to stderr if level is <= WARN:
use tracing::Level;
use tracing_subscriber::fmt::{self, writer::MakeWriterExt};
let stderr = std::io::stderr.with_max_level(Level::WARN);
let layer = fmt::layer()
.map_writer(move |w| stderr.or_else(w));
sourceimpl<S, N, L, T, W> Layer<S, N, Format<L, T>, W> where
N: for<'writer> FormatFields<'writer> + 'static,
impl<S, N, L, T, W> Layer<S, N, Format<L, T>, W> where
N: for<'writer> FormatFields<'writer> + 'static,
sourcepub fn with_timer<T2>(self, timer: T2) -> Layer<S, N, Format<L, T2>, W>
pub fn with_timer<T2>(self, timer: T2) -> Layer<S, N, Format<L, T2>, W>
Use the given timer
for span and event timestamps.
See the time
module for the provided timer implementations.
Note that using the "time
“” feature flag enables the
additional time formatters UtcTime
and LocalTime
, which use the
time
crate to provide more sophisticated timestamp formatting
options.
sourcepub fn without_time(self) -> Layer<S, N, Format<L, ()>, W>
pub fn without_time(self) -> Layer<S, N, Format<L, ()>, W>
Do not emit timestamps with spans and event.
sourcepub fn with_span_events(self, kind: FmtSpan) -> Self
pub fn with_span_events(self, kind: FmtSpan) -> Self
Configures how synthesized events are emitted at points in the span lifecycle.
The following options are available:
FmtSpan::NONE
: No events will be synthesized when spans are created, entered, exited, or closed. Data from spans will still be included as the context for formatted events. This is the default.FmtSpan::NEW
: An event will be synthesized when spans are created.FmtSpan::ENTER
: An event will be synthesized when spans are entered.FmtSpan::EXIT
: An event will be synthesized when spans are exited.FmtSpan::CLOSE
: An event will be synthesized when a span closes. If timestamps are enabled for this formatter, the generated event will contain fields with the span’s busy time (the total time for which it was entered) and idle time (the total time that the span existed but was not entered).FmtSpan::ACTIVE
: Events will be synthesized when spans are entered or exited.FmtSpan::FULL
: Events will be synthesized whenever a span is created, entered, exited, or closed. If timestamps are enabled, the close event will contain the span’s busy and idle time, as described above.
The options can be enabled in any combination. For instance, the following will synthesize events whenever spans are created and closed:
use tracing_subscriber::fmt;
use tracing_subscriber::fmt::format::FmtSpan;
let subscriber = fmt()
.with_span_events(FmtSpan::NEW | FmtSpan::CLOSE)
.finish();
Note that the generated events will only be part of the log output by
this formatter; they will not be recorded by other Subscriber
s or by
Layer
s added to this subscriber.
sourcepub fn with_target(self, display_target: bool) -> Layer<S, N, Format<L, T>, W>
pub fn with_target(self, display_target: bool) -> Layer<S, N, Format<L, T>, W>
Sets whether or not an event’s target is displayed.
sourcepub fn with_file(self, display_filename: bool) -> Layer<S, N, Format<L, T>, W>
pub fn with_file(self, display_filename: bool) -> Layer<S, N, Format<L, T>, W>
Sets whether or not an event’s source code file path is displayed.
sourcepub fn with_line_number(
self,
display_line_number: bool
) -> Layer<S, N, Format<L, T>, W>
pub fn with_line_number(
self,
display_line_number: bool
) -> Layer<S, N, Format<L, T>, W>
Sets whether or not an event’s source code line number is displayed.
sourcepub fn with_level(self, display_level: bool) -> Layer<S, N, Format<L, T>, W>
pub fn with_level(self, display_level: bool) -> Layer<S, N, Format<L, T>, W>
Sets whether or not an event’s level is displayed.
sourcepub fn with_thread_ids(
self,
display_thread_ids: bool
) -> Layer<S, N, Format<L, T>, W>
pub fn with_thread_ids(
self,
display_thread_ids: bool
) -> Layer<S, N, Format<L, T>, W>
Sets whether or not the thread ID of the current thread is displayed when formatting events
sourcepub fn with_thread_names(
self,
display_thread_names: bool
) -> Layer<S, N, Format<L, T>, W>
pub fn with_thread_names(
self,
display_thread_names: bool
) -> Layer<S, N, Format<L, T>, W>
Sets whether or not the name of the current thread is displayed when formatting events
sourcepub fn compact(self) -> Layer<S, N, Format<Compact, T>, W> where
N: for<'writer> FormatFields<'writer> + 'static,
pub fn compact(self) -> Layer<S, N, Format<Compact, T>, W> where
N: for<'writer> FormatFields<'writer> + 'static,
Sets the layer being built to use a less verbose formatter.
sourceimpl<S, N, E, W> Layer<S, N, E, W>
impl<S, N, E, W> Layer<S, N, E, W>
sourcepub fn fmt_fields<N2>(self, fmt_fields: N2) -> Layer<S, N2, E, W> where
N2: for<'writer> FormatFields<'writer> + 'static,
pub fn fmt_fields<N2>(self, fmt_fields: N2) -> Layer<S, N2, E, W> where
N2: for<'writer> FormatFields<'writer> + 'static,
Sets the field formatter that the layer being built will use to record fields.
sourcepub fn map_fmt_fields<N2>(self, f: impl FnOnce(N) -> N2) -> Layer<S, N2, E, W> where
N2: for<'writer> FormatFields<'writer> + 'static,
pub fn map_fmt_fields<N2>(self, f: impl FnOnce(N) -> N2) -> Layer<S, N2, E, W> where
N2: for<'writer> FormatFields<'writer> + 'static,
Updates the field formatter by applying a function to the existing field formatter.
This sets the field formatter that the layer being built will use to record fields.
Examples
Updating a field formatter:
use tracing_subscriber::field::MakeExt;
let layer = tracing_subscriber::fmt::layer()
.map_fmt_fields(|f| f.debug_alt());
Trait Implementations
sourceimpl<S, N, E, W> Layer<S> for Layer<S, N, E, W> where
S: Subscriber + for<'a> LookupSpan<'a>,
N: for<'writer> FormatFields<'writer> + 'static,
E: FormatEvent<S, N> + 'static,
W: for<'writer> MakeWriter<'writer> + 'static,
impl<S, N, E, W> Layer<S> for Layer<S, N, E, W> where
S: Subscriber + for<'a> LookupSpan<'a>,
N: for<'writer> FormatFields<'writer> + 'static,
E: FormatEvent<S, N> + 'static,
W: for<'writer> MakeWriter<'writer> + 'static,
sourcefn on_new_span(&self, attrs: &Attributes<'_>, id: &Id, ctx: Context<'_, S>)
fn on_new_span(&self, attrs: &Attributes<'_>, id: &Id, ctx: Context<'_, S>)
Notifies this layer that a new span was constructed with the given
Attributes
and Id
. Read more
sourcefn on_record(&self, id: &Id, values: &Record<'_>, ctx: Context<'_, S>)
fn on_record(&self, id: &Id, values: &Record<'_>, ctx: Context<'_, S>)
Notifies this layer that a span with the given Id
recorded the given
values
. Read more
sourcefn on_enter(&self, id: &Id, ctx: Context<'_, S>)
fn on_enter(&self, id: &Id, ctx: Context<'_, S>)
Notifies this layer that a span with the given ID was entered.
sourcefn on_exit(&self, id: &Id, ctx: Context<'_, S>)
fn on_exit(&self, id: &Id, ctx: Context<'_, S>)
Notifies this layer that the span with the given ID was exited.
sourcefn on_close(&self, id: Id, ctx: Context<'_, S>)
fn on_close(&self, id: Id, ctx: Context<'_, S>)
Notifies this layer that the span with the given ID has been closed.
sourcefn on_event(&self, event: &Event<'_>, ctx: Context<'_, S>)
fn on_event(&self, event: &Event<'_>, ctx: Context<'_, S>)
Notifies this layer that an event has occurred.
sourcefn on_layer(&mut self, subscriber: &mut S)
fn on_layer(&mut self, subscriber: &mut S)
Performs late initialization when attaching a Layer
to a
Subscriber
. Read more
sourcefn register_callsite(&self, metadata: &'static Metadata<'static>) -> Interest
fn register_callsite(&self, metadata: &'static Metadata<'static>) -> Interest
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
sourcefn enabled(&self, metadata: &Metadata<'_>, ctx: Context<'_, S>) -> bool
fn enabled(&self, metadata: &Metadata<'_>, ctx: Context<'_, S>) -> bool
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
sourcefn on_follows_from(&self, _span: &Id, _follows: &Id, _ctx: Context<'_, S>)
fn on_follows_from(&self, _span: &Id, _follows: &Id, _ctx: Context<'_, S>)
Notifies this layer that a span with the ID span
recorded that it
follows from the span with the ID follows
. Read more
sourcefn on_id_change(&self, _old: &Id, _new: &Id, _ctx: Context<'_, S>)
fn on_id_change(&self, _old: &Id, _new: &Id, _ctx: Context<'_, S>)
Notifies this layer that a span ID has been cloned, and that the subscriber returned a different ID. Read more
sourcefn and_then<L>(self, layer: L) -> Layered<L, Self, S> where
L: Layer<S>,
Self: Sized,
fn and_then<L>(self, layer: L) -> Layered<L, Self, S> where
L: Layer<S>,
Self: Sized,
Composes this layer around the given Layer
, returning a Layered
struct implementing Layer
. Read more
sourcefn with_subscriber(self, inner: S) -> Layered<Self, S> where
Self: Sized,
fn with_subscriber(self, inner: S) -> Layered<Self, S> where
Self: Sized,
Composes this Layer
with the given Subscriber
, returning a
Layered
struct that implements Subscriber
. Read more
sourcefn with_filter<F>(self, filter: F) -> Filtered<Self, F, S> where
Self: Sized,
F: Filter<S>,
fn with_filter<F>(self, filter: F) -> Filtered<Self, F, S> where
Self: Sized,
F: Filter<S>,
Auto Trait Implementations
impl<S, N, E, W> RefUnwindSafe for Layer<S, N, E, W> where
E: RefUnwindSafe,
N: RefUnwindSafe,
W: RefUnwindSafe,
impl<S, N, E, W> Send for Layer<S, N, E, W> where
E: Send,
N: Send,
W: Send,
impl<S, N, E, W> Sync for Layer<S, N, E, W> where
E: Sync,
N: Sync,
W: Sync,
impl<S, N, E, W> Unpin for Layer<S, N, E, W> where
E: Unpin,
N: Unpin,
W: Unpin,
impl<S, N, E, W> UnwindSafe for Layer<S, N, E, W> where
E: UnwindSafe,
N: UnwindSafe,
W: UnwindSafe,
Blanket Implementations
sourceimpl<T> BorrowMut<T> for T where
T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
const: unstable · sourcefn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
Mutably borrows from an owned value. Read more