Struct JsonLayer 

pub struct JsonLayer<W, T = SystemTimestamp> { /* private fields */ }

A tracing_subscriber::Layer that formats events as JSON lines.

See the crate-level docs for configuration options and output format details.

Implementations

impl<W> JsonLayer<W>

where W: for<'w> MakeWriter<'w> + 'static,

pub fn new(make_writer: W) -> Self

Create a new JsonLayer that writes JSON lines to make_writer.

Accepts anything implementing tracing_subscriber::fmt::MakeWriter, e.g. std::io::stderr or std::io::stdout.

impl<W, T> JsonLayer<W, T>

where W: for<'w> MakeWriter<'w> + 'static,

pub fn with_target(self, display_target: bool) -> Self

Set whether the target field (module path) is included in output.

Default: true.

pub fn with_file(self, display_filename: bool) -> Self

Set whether the filename field is included in output.

Default: false.

pub fn with_line_number(self, display_line: bool) -> Self

Set whether the line_number field is included in output.

Default: false.

pub fn with_thread_ids(self, display_thread_id: bool) -> Self

Set whether the threadId field is included in output.

Default: false.

pub fn with_thread_names(self, display_thread_name: bool) -> Self

Set whether the threadName field is included in output.

Default: false.

pub fn flatten_event(self, flatten: bool) -> Self

Set whether event fields are flattened to the top level of the JSON object instead of being nested under a "fields" key.

Default: false (fields are nested).

pub fn with_timer<T2: FormatTime>(self, timer: T2) -> JsonLayer<W, T2>

Use a custom FormatTime implementation for timestamps.

This replaces the default SystemTimestamp formatter. Any type implementing FormatTime can be used, including those from tracing-subscriber such as Uptime and ChronoUtc.

Pass () to disable timestamps entirely (equivalent to without_time).

pub fn without_time(self) -> JsonLayer<W, ()>

Disable timestamps in the output.

This is a convenience for self.with_timer(()).

Trait Implementations

impl<S, W, T> Layer<S> for JsonLayer<W, T>

where S: Subscriber + for<'a> LookupSpan<'a>, W: for<'w> MakeWriter<'w> + 'static, T: FormatTime + 'static,

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.

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.

fn on_event(&self, event: &Event<'_>, ctx: Context<'_, S>)

Notifies this layer that an event has occurred.

fn on_register_dispatch(&self, subscriber: &Dispatch)

Performs late initialization when installing this layer as a Subscriber.

fn on_layer(&mut self, subscriber: &mut S)

Performs late initialization when attaching a Layer to a Subscriber.

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.

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.

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.

fn event_enabled(&self, _event: &Event<'_>, _ctx: Context<'_, S>) -> bool

Called before on_event, to determine if on_event should be called.

fn on_enter(&self, _id: &Id, _ctx: Context<'_, S>)

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

fn on_exit(&self, _id: &Id, _ctx: Context<'_, S>)

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

fn on_close(&self, _id: Id, _ctx: Context<'_, S>)

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

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.

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.

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.

fn with_filter<F>(self, filter: F) -> Filtered<Self, F, S>

where Self: Sized, F: Filter<S>,

Combines self with a Filter, returning a Filtered layer.

fn boxed(self) -> Box<dyn Layer<S> + Send + Sync>

where Self: Sized + Layer<S> + Send + Sync + 'static, S: Subscriber,

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