opentelemetry_sdk/metrics/
reader.rs

1//! Interfaces for reading and producing metrics
2use std::{fmt, sync::Weak};
3
4use crate::{error::OTelSdkResult, metrics::MetricResult};
5
6use super::{data::ResourceMetrics, pipeline::Pipeline, InstrumentKind, Temporality};
7
8/// The interface used between the SDK and an exporter.
9///
10/// Control flow is bi-directional through the `MetricReader`, since the SDK
11/// initiates `force_flush` and `shutdown` while the reader initiates
12/// collection. The `register_pipeline` method here informs the metric reader
13/// that it can begin reading, signaling the start of bi-directional control
14/// flow.
15///
16/// Typically, push-based exporters that are periodic will implement
17/// `MetricExporter` themselves and construct a `PeriodicReader` to satisfy this
18/// interface.
19///
20/// Pull-based exporters will typically implement `MetricReader` themselves,
21/// since they read on demand.
22pub trait MetricReader: fmt::Debug + Send + Sync + 'static {
23    /// Registers a [MetricReader] with a [Pipeline].
24    ///
25    /// The pipeline argument allows the `MetricReader` to signal the sdk to collect
26    /// and send aggregated metric measurements.
27    fn register_pipeline(&self, pipeline: Weak<Pipeline>);
28
29    /// Gathers and returns all metric data related to the [MetricReader] from the
30    /// SDK and stores it in the provided [ResourceMetrics] reference.
31    ///
32    /// An error is returned if this is called after shutdown.
33    fn collect(&self, rm: &mut ResourceMetrics) -> MetricResult<()>;
34
35    /// Flushes all metric measurements held in an export pipeline.
36    ///
37    /// There is no guaranteed that all telemetry be flushed or all resources have
38    /// been released on error.
39    fn force_flush(&self) -> OTelSdkResult;
40
41    /// Flushes all metric measurements held in an export pipeline and releases any
42    /// held computational resources.
43    ///
44    /// There is no guaranteed that all telemetry be flushed or all resources have
45    /// been released on error.
46    ///
47    /// After `shutdown` is called, calls to `collect` will perform no operation and
48    /// instead will return an error indicating the shutdown state.
49    fn shutdown(&self) -> OTelSdkResult;
50
51    /// The output temporality, a function of instrument kind.
52    /// This SHOULD be obtained from the exporter.
53    ///
54    /// If not configured, the Cumulative temporality SHOULD be used.
55    fn temporality(&self, kind: InstrumentKind) -> Temporality;
56}
57
58/// Produces metrics for a [MetricReader].
59pub(crate) trait SdkProducer: fmt::Debug + Send + Sync {
60    /// Returns aggregated metrics from a single collection.
61    fn produce(&self, rm: &mut ResourceMetrics) -> MetricResult<()>;
62}
opentelemetry_sdk/metrics/reader.rs

opentelemetry_sdk/metrics/
reader.rs
