-
Notifications
You must be signed in to change notification settings - Fork 658
/
reload.rs
243 lines (208 loc) · 7.32 KB
/
reload.rs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
//! Wrapper for a `Collect` or `Subscribe` to allow it to be dynamically reloaded.
//!
//! This module provides a type implementing [`Subscribe`] which wraps another type implementing
//! the [`Subscribe`] trait, allowing the wrapped type to be replaced with another
//! instance of that type at runtime.
//!
//! This can be used in cases where a subset of `Collect` functionality
//! should be dynamically reconfigured, such as when filtering directives may
//! change at runtime. Note that this subscriber introduces a (relatively small)
//! amount of overhead, and should thus only be used as needed.
//!
//! [`Subscribe`]: crate::Subscribe
use crate::subscribe;
use crate::sync::RwLock;
use std::{
error, fmt,
sync::{Arc, Weak},
};
use tracing_core::{
callsite,
collect::{Collect, Interest},
span, Event, Metadata,
};
/// Wraps a `Collect` or `Subscribe`, allowing it to be reloaded dynamically at runtime.
#[derive(Debug)]
pub struct Subscriber<S> {
// 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<S>>,
}
/// Allows reloading the state of an associated `Collect`.
#[derive(Debug)]
pub struct Handle<S> {
inner: Weak<RwLock<S>>,
}
/// Indicates that an error occurred when reloading a subscriber.
#[derive(Debug)]
pub struct Error {
kind: ErrorKind,
}
#[derive(Debug)]
enum ErrorKind {
CollectorGone,
Poisoned,
}
// ===== impl Collect =====
impl<S, C> crate::Subscribe<C> for Subscriber<S>
where
S: crate::Subscribe<C> + 'static,
C: Collect,
{
#[inline]
fn register_callsite(&self, metadata: &'static Metadata<'static>) -> Interest {
try_lock!(self.inner.read(), else return Interest::sometimes()).register_callsite(metadata)
}
#[inline]
fn enabled(&self, metadata: &Metadata<'_>, ctx: subscribe::Context<'_, C>) -> bool {
try_lock!(self.inner.read(), else return false).enabled(metadata, ctx)
}
#[inline]
fn on_new_span(
&self,
attrs: &span::Attributes<'_>,
id: &span::Id,
ctx: subscribe::Context<'_, C>,
) {
try_lock!(self.inner.read()).on_new_span(attrs, id, ctx)
}
#[inline]
fn on_record(
&self,
span: &span::Id,
values: &span::Record<'_>,
ctx: subscribe::Context<'_, C>,
) {
try_lock!(self.inner.read()).on_record(span, values, ctx)
}
#[inline]
fn on_follows_from(&self, span: &span::Id, follows: &span::Id, ctx: subscribe::Context<'_, C>) {
try_lock!(self.inner.read()).on_follows_from(span, follows, ctx)
}
#[inline]
fn event_enabled(&self, event: &Event<'_>, ctx: subscribe::Context<'_, C>) -> bool {
try_lock!(self.inner.read(), else return false).event_enabled(event, ctx)
}
#[inline]
fn on_event(&self, event: &Event<'_>, ctx: subscribe::Context<'_, C>) {
try_lock!(self.inner.read()).on_event(event, ctx)
}
#[inline]
fn on_enter(&self, id: &span::Id, ctx: subscribe::Context<'_, C>) {
try_lock!(self.inner.read()).on_enter(id, ctx)
}
#[inline]
fn on_exit(&self, id: &span::Id, ctx: subscribe::Context<'_, C>) {
try_lock!(self.inner.read()).on_exit(id, ctx)
}
#[inline]
fn on_close(&self, id: span::Id, ctx: subscribe::Context<'_, C>) {
try_lock!(self.inner.read()).on_close(id, ctx)
}
#[inline]
fn on_id_change(&self, old: &span::Id, new: &span::Id, ctx: subscribe::Context<'_, C>) {
try_lock!(self.inner.read()).on_id_change(old, new, ctx)
}
}
impl<S> Subscriber<S> {
/// Wraps the given `Subscribe`, returning a subscriber and a `Handle` that allows
/// the inner type to be modified at runtime.
pub fn new(inner: S) -> (Self, Handle<S>) {
let this = Self {
inner: Arc::new(RwLock::new(inner)),
};
let handle = this.handle();
(this, handle)
}
/// Returns a `Handle` that can be used to reload the wrapped `Subscribe`.
pub fn handle(&self) -> Handle<S> {
Handle {
inner: Arc::downgrade(&self.inner),
}
}
}
// ===== impl Handle =====
impl<S> Handle<S> {
/// Replace the current subscriber with the provided `new_subscriber`.
pub fn reload(&self, new_subscriber: impl Into<S>) -> Result<(), Error> {
self.modify(|subscriber| {
*subscriber = new_subscriber.into();
})
}
/// Invokes a closure with a mutable reference to the current subscriber,
/// allowing it to be modified in place.
pub fn modify(&self, f: impl FnOnce(&mut S)) -> Result<(), Error> {
let inner = self.inner.upgrade().ok_or(Error {
kind: ErrorKind::CollectorGone,
})?;
let mut lock = try_lock!(inner.write(), else return Err(Error::poisoned()));
f(&mut *lock);
// Release the lock before rebuilding the interest cache, as that
// function will lock the new subscriber.
drop(lock);
callsite::rebuild_interest_cache();
// If the `log` crate compatibility feature is in use, set `log`'s max
// level as well, in case the max `tracing` level changed. We do this
// *after* rebuilding the interest cache, as that's when the `tracing`
// max level filter is re-computed.
#[cfg(feature = "tracing-log")]
tracing_log::log::set_max_level(tracing_log::AsLog::as_log(
&crate::filter::LevelFilter::current(),
));
Ok(())
}
/// Returns a clone of the subscriber's current value if it still exists.
/// Otherwise, if the collector has been dropped, returns `None`.
pub fn clone_current(&self) -> Option<S>
where
S: Clone,
{
self.with_current(S::clone).ok()
}
/// Invokes a closure with a borrowed reference to the current subscriber,
/// returning the result (or an error if the collector no longer exists).
pub fn with_current<T>(&self, f: impl FnOnce(&S) -> T) -> Result<T, Error> {
let inner = self.inner.upgrade().ok_or(Error {
kind: ErrorKind::CollectorGone,
})?;
let inner = try_lock!(inner.read(), else return Err(Error::poisoned()));
Ok(f(&*inner))
}
}
impl<S> Clone for Handle<S> {
fn clone(&self) -> Self {
Handle {
inner: self.inner.clone(),
}
}
}
// ===== impl Error =====
impl Error {
fn poisoned() -> Self {
Self {
kind: ErrorKind::Poisoned,
}
}
/// Returns `true` if this error occurred because the subscriber was poisoned by
/// a panic on another thread.
pub fn is_poisoned(&self) -> bool {
matches!(self.kind, ErrorKind::Poisoned)
}
/// Returns `true` if this error occurred because the `Collector`
/// containing the reloadable subscriber was dropped.
pub fn is_dropped(&self) -> bool {
matches!(self.kind, ErrorKind::CollectorGone)
}
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
let msg = match self.kind {
ErrorKind::CollectorGone => "subscriber no longer exists",
ErrorKind::Poisoned => "lock poisoned",
};
f.pad(msg)
}
}
impl error::Error for Error {}