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subscriber: fix reload ergonomics #1035

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Oct 13, 2020
Merged

subscriber: fix reload ergonomics #1035

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8a87ea5
subscriber: fix `reload` ergonomics
hawkw Oct 13, 2020
a8d564c
fix rustdoc links
hawkw Oct 13, 2020
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23 changes: 7 additions & 16 deletions examples/examples/tower-load.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -185,23 +185,20 @@ impl<T> Service<T> for MakeSvc {
}
}

struct AdminSvc<S> {
handle: Handle<EnvFilter, S>,
struct AdminSvc {
handle: Handle<EnvFilter>,
}

impl<S> Clone for AdminSvc<S> {
impl Clone for AdminSvc {
fn clone(&self) -> Self {
Self {
handle: self.handle.clone(),
}
}
}

impl<'a, S> Service<&'a AddrStream> for AdminSvc<S>
where
S: tracing::Subscriber,
{
type Response = AdminSvc<S>;
impl<'a> Service<&'a AddrStream> for AdminSvc {
type Response = AdminSvc;
type Error = hyper::Error;
type Future = Ready<Result<Self::Response, Self::Error>>;

Expand All @@ -214,10 +211,7 @@ where
}
}

impl<S> Service<Request<Body>> for AdminSvc<S>
where
S: tracing::Subscriber + 'static,
{
impl Service<Request<Body>> for AdminSvc {
type Response = Response<Body>;
type Error = Err;
type Future = Pin<Box<dyn Future<Output = Result<Response<Body>, Err>> + std::marker::Send>>;
Expand Down Expand Up @@ -252,10 +246,7 @@ where
}
}

impl<S> AdminSvc<S>
where
S: tracing::Subscriber + 'static,
{
impl AdminSvc {
fn set_from(&self, bytes: Bytes) -> Result<(), String> {
use std::str;
let body = str::from_utf8(&bytes.as_ref()).map_err(|e| format!("{}", e))?;
Expand Down
72 changes: 48 additions & 24 deletions tracing-subscriber/src/fmt/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -137,6 +137,7 @@ use crate::{
filter::LevelFilter,
layer,
registry::{LookupSpan, Registry},
reload,
};

#[doc(inline)]
Expand Down Expand Up @@ -646,35 +647,13 @@ impl<T, F, W> SubscriberBuilder<format::JsonFields, format::Format<format::Json,
}
}

#[cfg(feature = "env-filter")]
#[cfg_attr(docsrs, doc(cfg(feature = "env-filter")))]
impl<N, E, W> SubscriberBuilder<N, E, crate::EnvFilter, W>
where
Formatter<N, E, W>: tracing_core::Subscriber + 'static,
{
/// Configures the subscriber being built to allow filter reloading at
/// runtime.
pub fn with_filter_reloading(
self,
) -> SubscriberBuilder<N, E, crate::reload::Layer<crate::EnvFilter, Formatter<N, E, W>>, W>
{
let (filter, _) = crate::reload::Layer::new(self.filter);
SubscriberBuilder {
filter,
inner: self.inner,
}
}
}

#[cfg(feature = "env-filter")]
#[cfg_attr(docsrs, doc(cfg(feature = "env-filter")))]
impl<N, E, W> SubscriberBuilder<N, E, crate::reload::Layer<crate::EnvFilter, Formatter<N, E, W>>, W>
impl<N, E, F, W> SubscriberBuilder<N, E, reload::Layer<F>, W>
where
Formatter<N, E, W>: tracing_core::Subscriber + 'static,
{
/// Returns a `Handle` that may be used to reload the constructed subscriber's
/// filter.
pub fn reload_handle(&self) -> crate::reload::Handle<crate::EnvFilter, Formatter<N, E, W>> {
pub fn reload_handle(&self) -> reload::Handle<F> {
self.filter.handle()
}
}
Expand Down Expand Up @@ -814,6 +793,51 @@ impl<N, E, F, W> SubscriberBuilder<N, E, F, W> {
}
}

/// Configures the subscriber being built to allow filter reloading at
/// runtime.
///
/// The returned builder will have a [`reload_handle`] method, which returns
/// a [`reload::Handle`] that may be used to set a new filter value.
///
/// For example:
///
/// ```
/// use tracing::Level;
/// use tracing_subscriber::prelude::*;
///
/// let builder = tracing_subscriber::fmt()
/// // Set a max level filter on the subscriber
/// .with_max_level(Level::INFO)
/// .with_filter_reloading();
///
/// // Get a handle for modifying the subscriber's max level filter.
/// let handle = builder.reload_handle();
///
/// // Finish building the subscriber, and set it as the default.
/// builder.finish().init();
///
/// // Currently, the max level is INFO, so this event will be disabled.
/// tracing::debug!("this is not recorded!");
///
/// // Use the handle to set a new max level filter.
/// // (this returns an error if the subscriber has been dropped, which shouldn't
/// // happen in this example.)
/// handle.reload(Level::DEBUG).expect("the subscriber should still exist");
///
/// // Now, the max level is INFO, so this event will be recorded.
/// tracing::debug!("this is recorded!");
/// ```
///
/// [`reload_handle`]: SubscriberBuilder::reload_handle
/// [`reload::Handle`]: crate::reload::Handle
pub fn with_filter_reloading(self) -> SubscriberBuilder<N, E, reload::Layer<F>, W> {
let (filter, _) = reload::Layer::new(self.filter);
SubscriberBuilder {
filter,
inner: self.inner,
}
}

/// Sets the function that the subscriber being built should use to format
/// events that occur.
pub fn event_format<E2>(self, fmt_event: E2) -> SubscriberBuilder<N, E2, F, W>
Expand Down
30 changes: 8 additions & 22 deletions tracing-subscriber/src/reload.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,6 @@ use crate::sync::RwLock;

use std::{
error, fmt,
marker::PhantomData,
sync::{Arc, Weak},
};
use tracing_core::{
Expand All @@ -27,20 +26,18 @@ use tracing_core::{

/// Wraps a `Layer`, allowing it to be reloaded dynamically at runtime.
#[derive(Debug)]
pub struct Layer<L, S> {
pub struct Layer<L> {
// TODO(eliza): this once used a `crossbeam_util::ShardedRwLock`. We may
// eventually wish to replace it with a sharded lock implementation on top
// of our internal `RwLock` wrapper type. If possible, we should profile
// this first to determine if it's necessary.
inner: Arc<RwLock<L>>,
_s: PhantomData<fn(S)>,
}

/// Allows reloading the state of an associated `Layer`.
#[derive(Debug)]
pub struct Handle<L, S> {
pub struct Handle<L> {
inner: Weak<RwLock<L>>,
_s: PhantomData<fn(S)>,
}

/// Indicates that an error occurred when reloading a layer.
Expand All @@ -57,7 +54,7 @@ enum ErrorKind {

// ===== impl Layer =====

impl<L, S> crate::Layer<S> for Layer<L, S>
impl<L, S> crate::Layer<S> for Layer<L>
where
L: crate::Layer<S> + 'static,
S: Subscriber,
Expand Down Expand Up @@ -113,38 +110,28 @@ where
}
}

impl<L, S> Layer<L, S>
where
L: crate::Layer<S> + 'static,
S: Subscriber,
{
impl<L> Layer<L> {
/// Wraps the given `Layer`, returning a `Layer` and a `Handle` that allows
/// the inner type to be modified at runtime.
pub fn new(inner: L) -> (Self, Handle<L, S>) {
pub fn new(inner: L) -> (Self, Handle<L>) {
let this = Self {
inner: Arc::new(RwLock::new(inner)),
_s: PhantomData,
};
let handle = this.handle();
(this, handle)
}

/// Returns a `Handle` that can be used to reload the wrapped `Layer`.
pub fn handle(&self) -> Handle<L, S> {
pub fn handle(&self) -> Handle<L> {
Handle {
inner: Arc::downgrade(&self.inner),
_s: PhantomData,
}
}
}

// ===== impl Handle =====

impl<L, S> Handle<L, S>
where
L: crate::Layer<S> + 'static,
S: Subscriber,
{
impl<L> Handle<L> {
/// Replace the current layer with the provided `new_layer`.
pub fn reload(&self, new_layer: impl Into<L>) -> Result<(), Error> {
self.modify(|layer| {
Expand Down Expand Up @@ -189,11 +176,10 @@ where
}
}

impl<L, S> Clone for Handle<L, S> {
impl<L> Clone for Handle<L> {
fn clone(&self) -> Self {
Handle {
inner: self.inner.clone(),
_s: PhantomData,
}
}
}
Expand Down