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//! Debugging utilities.
//!
//! While these utilities are primarily designed to help aid with testing and debugging of exporters
//! and core parts of the `metrics` ecosystem, they can be beneficial for in-process collecting of
//! metrics in some limited cases.
use std::{
cell::RefCell,
collections::HashMap,
fmt::Debug,
hash::Hash,
sync::{atomic::Ordering, Arc, Mutex},
};
use crate::{
kind::MetricKind,
registry::{AtomicStorage, Registry},
CompositeKey,
};
use indexmap::IndexMap;
use metrics::{Counter, Gauge, Histogram, Key, KeyName, Recorder, SharedString, Unit};
use ordered_float::OrderedFloat;
thread_local! {
/// A per-thread version of the debugging registry/state used only when the debugging recorder is configured to run in per-thread mode.
static PER_THREAD_INNER: RefCell<Option<Inner>> = RefCell::new(None);
}
/// A composite key name that stores both the metric key name and the metric kind.
#[derive(Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
struct CompositeKeyName(MetricKind, KeyName);
impl CompositeKeyName {
/// Creates a new `CompositeKeyName`.
pub const fn new(kind: MetricKind, key_name: KeyName) -> CompositeKeyName {
CompositeKeyName(kind, key_name)
}
}
/// A point-in-time snapshot of all metrics in [`DebuggingRecorder`].
pub struct Snapshot(Vec<(CompositeKey, Option<Unit>, Option<SharedString>, DebugValue)>);
impl Snapshot {
/// Converts this snapshot to a mapping of metric data, keyed by the metric key itself.
#[allow(clippy::mutable_key_type)]
pub fn into_hashmap(
self,
) -> HashMap<CompositeKey, (Option<Unit>, Option<SharedString>, DebugValue)> {
self.0
.into_iter()
.map(|(k, unit, desc, value)| (k, (unit, desc, value)))
.collect::<HashMap<_, _>>()
}
/// Converts this snapshot to a vector of metric data tuples.
pub fn into_vec(self) -> Vec<(CompositeKey, Option<Unit>, Option<SharedString>, DebugValue)> {
self.0
}
}
/// A point-in-time value for a metric exposing raw values.
#[derive(Debug, PartialEq, Eq, Hash)]
pub enum DebugValue {
/// Counter.
Counter(u64),
/// Gauge.
Gauge(OrderedFloat<f64>),
/// Histogram.
Histogram(Vec<OrderedFloat<f64>>),
}
struct Inner {
registry: Registry<Key, AtomicStorage>,
seen: Mutex<IndexMap<CompositeKey, ()>>,
metadata: Mutex<IndexMap<CompositeKeyName, (Option<Unit>, SharedString)>>,
}
impl Inner {
fn new() -> Self {
Self {
registry: Registry::atomic(),
seen: Mutex::new(IndexMap::new()),
metadata: Mutex::new(IndexMap::new()),
}
}
}
/// Captures point-in-time snapshots of [`DebuggingRecorder`].
pub struct Snapshotter {
inner: Arc<Inner>,
}
impl Snapshotter {
/// Takes a snapshot of the recorder.
pub fn snapshot(&self) -> Snapshot {
let mut snapshot = Vec::new();
let counters = self.inner.registry.get_counter_handles();
let gauges = self.inner.registry.get_gauge_handles();
let histograms = self.inner.registry.get_histogram_handles();
let seen = self.inner.seen.lock().expect("seen lock poisoned").clone();
let metadata = self.inner.metadata.lock().expect("metadata lock poisoned").clone();
for (ck, _) in seen.into_iter() {
let value = match ck.kind() {
MetricKind::Counter => {
counters.get(ck.key()).map(|c| DebugValue::Counter(c.load(Ordering::SeqCst)))
}
MetricKind::Gauge => gauges.get(ck.key()).map(|g| {
let value = f64::from_bits(g.load(Ordering::SeqCst));
DebugValue::Gauge(value.into())
}),
MetricKind::Histogram => histograms.get(ck.key()).map(|h| {
let mut values = Vec::new();
h.clear_with(|xs| values.extend(xs.iter().map(|f| OrderedFloat::from(*f))));
DebugValue::Histogram(values)
}),
};
let ckn = CompositeKeyName::new(ck.kind(), ck.key().name().to_string().into());
let (unit, desc) = metadata
.get(&ckn)
.map(|(u, d)| (u.to_owned(), Some(d.to_owned())))
.unwrap_or_else(|| (None, None));
// If there's no value for the key, that means the metric was only ever described, and
// not registered, so don't emit it.
if let Some(value) = value {
snapshot.push((ck, unit, desc, value));
}
}
Snapshot(snapshot)
}
/// Takes a snapshot of the recorder for the current thread only.
///
/// If no registry exists for the current thread, `None` is returned. Otherwise, `Some(snapshot)` is returned.
pub fn current_thread_snapshot() -> Option<Snapshot> {
PER_THREAD_INNER.with(|maybe_inner| match maybe_inner.borrow().as_ref() {
None => None,
Some(inner) => {
let mut snapshot = Vec::new();
let counters = inner.registry.get_counter_handles();
let gauges = inner.registry.get_gauge_handles();
let histograms = inner.registry.get_histogram_handles();
let seen = inner.seen.lock().expect("seen lock poisoned").clone();
let metadata = inner.metadata.lock().expect("metadata lock poisoned").clone();
for (ck, _) in seen.into_iter() {
let value = match ck.kind() {
MetricKind::Counter => counters
.get(ck.key())
.map(|c| DebugValue::Counter(c.load(Ordering::SeqCst))),
MetricKind::Gauge => gauges.get(ck.key()).map(|g| {
let value = f64::from_bits(g.load(Ordering::SeqCst));
DebugValue::Gauge(value.into())
}),
MetricKind::Histogram => histograms.get(ck.key()).map(|h| {
let mut values = Vec::new();
h.clear_with(|xs| {
values.extend(xs.iter().map(|f| OrderedFloat::from(*f)))
});
DebugValue::Histogram(values)
}),
};
let ckn = CompositeKeyName::new(ck.kind(), ck.key().name().to_string().into());
let (unit, desc) = metadata
.get(&ckn)
.map(|(u, d)| (u.to_owned(), Some(d.to_owned())))
.unwrap_or_else(|| (None, None));
// If there's no value for the key, that means the metric was only ever described, and
// not registered, so don't emit it.
if let Some(value) = value {
snapshot.push((ck, unit, desc, value));
}
}
Some(Snapshot(snapshot))
}
})
}
}
/// A simplistic recorder that can be installed and used for debugging or testing.
///
/// Callers can easily take snapshots of the metrics at any given time and get access
/// to the raw values.
pub struct DebuggingRecorder {
inner: Arc<Inner>,
is_per_thread: bool,
}
impl DebuggingRecorder {
/// Creates a new `DebuggingRecorder`.
pub fn new() -> DebuggingRecorder {
DebuggingRecorder { inner: Arc::new(Inner::new()), is_per_thread: false }
}
/// Creates a new `DebuggingRecorder` in per-thread mode.
///
/// This sends all metrics to a per-thread registry, such that the snapshotter will only see metrics emitted in the
/// thread that the `Snapshotter` is used from. Additionally, as keeping a reference to the original `Snapshotter`
/// around can be tricky, [`Snapshotter::current_thread_snapshot`] can be used to get all of the metrics currently
/// present in the registry for the calling thread, if any were emitted.
///
/// Please note that this recorder must still be installed, but it can be installed multiple times (if the error
/// from `install` is ignored) without clearing or removing any of the existing per-thread metrics, so it's safe to
/// re-create and re-install multiple times in the same test binary if necessary.
pub fn per_thread() -> DebuggingRecorder {
DebuggingRecorder { inner: Arc::new(Inner::new()), is_per_thread: true }
}
/// Gets a `Snapshotter` attached to this recorder.
pub fn snapshotter(&self) -> Snapshotter {
Snapshotter { inner: Arc::clone(&self.inner) }
}
fn describe_metric(&self, rkey: CompositeKeyName, unit: Option<Unit>, desc: SharedString) {
if self.is_per_thread {
PER_THREAD_INNER.with(|cell| {
// Create the inner state if it doesn't yet exist.
//
// SAFETY: It's safe to use `borrow_mut` here, even though the parent method is `&self`, as this is a
// per-thread invocation, so no other caller could possibly be holding a referenced, immutable or
// mutable, at the same time.
let mut maybe_inner = cell.borrow_mut();
let inner = maybe_inner.get_or_insert_with(Inner::new);
let mut metadata = inner.metadata.lock().expect("metadata lock poisoned");
let (uentry, dentry) = metadata.entry(rkey).or_insert((None, desc.to_owned()));
if unit.is_some() {
*uentry = unit;
}
*dentry = desc.to_owned();
});
} else {
let mut metadata = self.inner.metadata.lock().expect("metadata lock poisoned");
let (uentry, dentry) = metadata.entry(rkey).or_insert((None, desc.to_owned()));
if unit.is_some() {
*uentry = unit;
}
*dentry = desc;
}
}
fn track_metric(&self, ckey: CompositeKey) {
if self.is_per_thread {
PER_THREAD_INNER.with(|cell| {
// Create the inner state if it doesn't yet exist.
//
// SAFETY: It's safe to use `borrow_mut` here, even though the parent method is `&self`, as this is a
// per-thread invocation, so no other caller could possibly be holding a referenced, immutable or
// mutable, at the same time.
let mut maybe_inner = cell.borrow_mut();
let inner = maybe_inner.get_or_insert_with(Inner::new);
let mut seen = inner.seen.lock().expect("seen lock poisoned");
seen.insert(ckey, ());
});
} else {
let mut seen = self.inner.seen.lock().expect("seen lock poisoned");
seen.insert(ckey, ());
}
}
/// Installs this recorder as the global recorder.
pub fn install(self) -> Result<(), metrics::SetRecorderError> {
metrics::set_boxed_recorder(Box::new(self))
}
}
impl Recorder for DebuggingRecorder {
fn describe_counter(&self, key: KeyName, unit: Option<Unit>, description: SharedString) {
let ckey = CompositeKeyName::new(MetricKind::Counter, key);
self.describe_metric(ckey, unit, description);
}
fn describe_gauge(&self, key: KeyName, unit: Option<Unit>, description: SharedString) {
let ckey = CompositeKeyName::new(MetricKind::Gauge, key);
self.describe_metric(ckey, unit, description);
}
fn describe_histogram(&self, key: KeyName, unit: Option<Unit>, description: SharedString) {
let ckey = CompositeKeyName::new(MetricKind::Histogram, key);
self.describe_metric(ckey, unit, description);
}
fn register_counter(&self, key: &Key) -> Counter {
let ckey = CompositeKey::new(MetricKind::Counter, key.clone());
self.track_metric(ckey);
if self.is_per_thread {
PER_THREAD_INNER.with(move |cell| {
// Create the inner state if it doesn't yet exist.
//
// SAFETY: It's safe to use `borrow_mut` here, even though the parent method is `&self`, as this is a
// per-thread invocation, so no other caller could possibly be holding a referenced, immutable or
// mutable, at the same time.
let mut maybe_inner = cell.borrow_mut();
let inner = maybe_inner.get_or_insert_with(Inner::new);
inner.registry.get_or_create_counter(key, |c| Counter::from_arc(c.clone()))
})
} else {
self.inner.registry.get_or_create_counter(key, |c| Counter::from_arc(c.clone()))
}
}
fn register_gauge(&self, key: &Key) -> Gauge {
let ckey = CompositeKey::new(MetricKind::Gauge, key.clone());
self.track_metric(ckey);
if self.is_per_thread {
PER_THREAD_INNER.with(move |cell| {
// Create the inner state if it doesn't yet exist.
//
// SAFETY: It's safe to use `borrow_mut` here, even though the parent method is `&self`, as this is a
// per-thread invocation, so no other caller could possibly be holding a referenced, immutable or
// mutable, at the same time.
let mut maybe_inner = cell.borrow_mut();
let inner = maybe_inner.get_or_insert_with(Inner::new);
inner.registry.get_or_create_gauge(key, |g| Gauge::from_arc(g.clone()))
})
} else {
self.inner.registry.get_or_create_gauge(key, |g| Gauge::from_arc(g.clone()))
}
}
fn register_histogram(&self, key: &Key) -> Histogram {
let ckey = CompositeKey::new(MetricKind::Histogram, key.clone());
self.track_metric(ckey);
if self.is_per_thread {
PER_THREAD_INNER.with(move |cell| {
// Create the inner state if it doesn't yet exist.
//
// SAFETY: It's safe to use `borrow_mut` here, even though the parent method is `&self`, as this is a
// per-thread invocation, so no other caller could possibly be holding a referenced, immutable or
// mutable, at the same time.
let mut maybe_inner = cell.borrow_mut();
let inner = maybe_inner.get_or_insert_with(Inner::new);
inner.registry.get_or_create_histogram(key, |h| Histogram::from_arc(h.clone()))
})
} else {
self.inner.registry.get_or_create_histogram(key, |h| Histogram::from_arc(h.clone()))
}
}
}
impl Default for DebuggingRecorder {
fn default() -> Self {
DebuggingRecorder::new()
}
}
#[cfg(test)]
mod tests {
use metrics::counter;
use crate::{CompositeKey, MetricKind};
use super::{DebugValue, DebuggingRecorder, Snapshotter};
#[test]
fn per_thread() {
// Create the recorder in per-thread mode, get the snapshotter, and then spawn two threads that record some
// metrics. Neither thread should see the metrics of the other, and this main thread running the test should see
// _any_ metrics.
let recorder = DebuggingRecorder::per_thread();
let snapshotter = recorder.snapshotter();
unsafe { metrics::clear_recorder() };
recorder.install().expect("installing debugging recorder should not fail");
let t1 = std::thread::spawn(|| {
counter!("test_counter", 43);
Snapshotter::current_thread_snapshot()
});
let t2 = std::thread::spawn(|| {
counter!("test_counter", 47);
Snapshotter::current_thread_snapshot()
});
let t1_result =
t1.join().expect("thread 1 should not fail").expect("thread 1 should have metrics");
let t2_result =
t2.join().expect("thread 2 should not fail").expect("thread 2 should have metrics");
let main_result = snapshotter.snapshot().into_vec();
assert!(main_result.is_empty());
assert_eq!(
t1_result.into_vec(),
vec![(
CompositeKey::new(MetricKind::Counter, "test_counter".into()),
None,
None,
DebugValue::Counter(43),
)]
);
assert_eq!(
t2_result.into_vec(),
vec![(
CompositeKey::new(MetricKind::Counter, "test_counter".into()),
None,
None,
DebugValue::Counter(47),
)]
);
}
}