Add experimental metrics implementation (#618)

Co-authored-by: Jan Michael Auer <[email protected]>

CHANGELOG.md

@@ -1,5 +1,13 @@
 # Changelog
 
+## Unreleased
+
+**Features**:
+
+- Add experimental implementations for Sentry metrics and a cadence sink. These
+  require to use the `UNSTABLE_metrics` and `UNSTABLE_cadence` feature flags.
+  Note that these APIs are still under development and subject to change.
+
 ## 0.32.0
 
 **Features**:

sentry-core/Cargo.toml

@@ -26,8 +26,11 @@ client = ["rand"]
 # and macros actually expand features (and extern crate) where they are used!
 debug-logs = ["dep:log"]
 test = ["client"]
+UNSTABLE_metrics = ["sentry-types/UNSTABLE_metrics"]
+UNSTABLE_cadence = ["dep:cadence", "UNSTABLE_metrics"]
 
 [dependencies]
+cadence = { version = "0.29.0", optional = true }
 log = { version = "0.4.8", optional = true, features = ["std"] }
 once_cell = "1"
 rand = { version = "0.8.1", optional = true }

sentry-core/src/cadence.rs

@@ -0,0 +1,162 @@
+//! [`cadence`] integration for Sentry.
+//!
+//! [`cadence`] is a popular Statsd client for Rust. The [`SentryMetricSink`] provides a drop-in
+//! integration to send metrics captured via `cadence` to Sentry. For direct usage of Sentry
+//! metrics, see the [`metrics`](crate::metrics) module.
+//!
+//! # Usage
+//!
+//! To use the `cadence` integration, enable the `UNSTABLE_cadence` feature in your `Cargo.toml`.
+//! Then, create a [`SentryMetricSink`] and pass it to your `cadence` client:
+//!
+//! ```
+//! use cadence::StatsdClient;
+//! use sentry::cadence::SentryMetricSink;
+//!
+//! let client = StatsdClient::from_sink("sentry.test", SentryMetricSink::new());
+//! ```
+//!
+//! # Side-by-side Usage
+//!
+//! If you want to send metrics to Sentry and another backend at the same time, you can use
+//! [`SentryMetricSink::wrap`] to wrap another [`MetricSink`]:
+//!
+//! ```
+//! use cadence::{StatsdClient, NopMetricSink};
+//! use sentry::cadence::SentryMetricSink;
+//!
+//! let sink = SentryMetricSink::wrap(NopMetricSink);
+//! let client = StatsdClient::from_sink("sentry.test", sink);
+//! ```
+
+use std::sync::Arc;
+
+use cadence::{MetricSink, NopMetricSink};
+
+use crate::metrics::Metric;
+use crate::{Client, Hub};
+
+/// A [`MetricSink`] that sends metrics to Sentry.
+///
+/// This metric sends all metrics to Sentry. The Sentry client is internally buffered, so submission
+/// will be delayed.
+///
+/// Optionally, this sink can also forward metrics to another [`MetricSink`]. This is useful if you
+/// want to send metrics to Sentry and another backend at the same time. Use
+/// [`SentryMetricSink::wrap`] to construct such a sink.
+#[derive(Debug)]
+pub struct SentryMetricSink<S = NopMetricSink> {
+    client: Option<Arc<Client>>,
+    sink: S,
+}
+
+impl<S> SentryMetricSink<S>
+where
+    S: MetricSink,
+{
+    /// Creates a new [`SentryMetricSink`], wrapping the given [`MetricSink`].
+    pub fn wrap(sink: S) -> Self {
+        Self { client: None, sink }
+    }
+
+    /// Creates a new [`SentryMetricSink`] sending data to the given [`Client`].
+    pub fn with_client(mut self, client: Arc<Client>) -> Self {
+        self.client = Some(client);
+        self
+    }
+}
+
+impl SentryMetricSink {
+    /// Creates a new [`SentryMetricSink`].
+    ///
+    /// It is not required that a client is available when this sink is created. The sink sends
+    /// metrics to the client of the Sentry hub that is registered when the metrics are emitted.
+    pub fn new() -> Self {
+        Self {
+            client: None,
+            sink: NopMetricSink,
+        }
+    }
+}
+
+impl Default for SentryMetricSink {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl MetricSink for SentryMetricSink {
+    fn emit(&self, string: &str) -> std::io::Result<usize> {
+        if let Ok(metric) = Metric::parse_statsd(string) {
+            if let Some(ref client) = self.client {
+                client.add_metric(metric);
+            } else if let Some(client) = Hub::current().client() {
+                client.add_metric(metric);
+            }
+        }
+
+        // NopMetricSink returns `0`, which is correct as Sentry is buffering the metrics.
+        self.sink.emit(string)
+    }
+
+    fn flush(&self) -> std::io::Result<()> {
+        let flushed = if let Some(ref client) = self.client {
+            client.flush(None)
+        } else if let Some(client) = Hub::current().client() {
+            client.flush(None)
+        } else {
+            true
+        };
+
+        let sink_result = self.sink.flush();
+
+        if !flushed {
+            Err(std::io::Error::new(
+                std::io::ErrorKind::Other,
+                "failed to flush metrics to Sentry",
+            ))
+        } else {
+            sink_result
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use cadence::{Counted, Distributed};
+    use sentry_types::protocol::latest::EnvelopeItem;
+
+    use crate::test::with_captured_envelopes;
+
+    use super::*;
+
+    #[test]
+    fn test_basic_metrics() {
+        let envelopes = with_captured_envelopes(|| {
+            let client = cadence::StatsdClient::from_sink("sentry.test", SentryMetricSink::new());
+            client.count("some.count", 1).unwrap();
+            client.count("some.count", 10).unwrap();
+            client
+                .count_with_tags("count.with.tags", 1)
+                .with_tag("foo", "bar")
+                .send();
+            client.distribution("some.distr", 1).unwrap();
+            client.distribution("some.distr", 2).unwrap();
+            client.distribution("some.distr", 3).unwrap();
+        });
+        assert_eq!(envelopes.len(), 1);
+
+        let mut items = envelopes[0].items();
+        let Some(EnvelopeItem::Statsd(metrics)) = items.next() else {
+            panic!("expected metrics");
+        };
+        let metrics = std::str::from_utf8(metrics).unwrap();
+
+        println!("{metrics}");
+
+        assert!(metrics.contains("sentry.test.count.with.tags:1|c|#foo:bar|T"));
+        assert!(metrics.contains("sentry.test.some.count:11|c|T"));
+        assert!(metrics.contains("sentry.test.some.distr:1:2:3|d|T"));
+        assert_eq!(items.next(), None);
+    }
+}