Remove opentelemetry as the default metrics library (#97)

* [WIP]

* Update prometheus-client version

* Finish support for prometheus-client

* Fix doc links

* Ensure that prometheus-client is actually being used

* Work on fixing tests, remove const_format dep

* Don't use regexes in tests (because different libraries order labels differently)

* Make once_cell a required dependency

* Rename concurrency tracker to gauge

* Move PROMETHEUS_CLIENT_REGISTRY to integrations module

* Run all the other tests first

* Run the tests in the same order

* The prometheus-exporter feature needs to depend on the prometheus feature (for now)

* Rename export to just REGISTRY

* Mention prometheus-client in readme and changelog

* Remove opentelemetry as the default metrics library

* Disable opentelemetry tests

* continue-on-error

* previously...

* Remove opentelemetry memory api call

* Fix error type

* Remove duplicate code

* Make metrics library features mutually exclusive

Author: emschwartz

.github/workflows/ci.yml

@@ -24,15 +24,18 @@ jobs:
       - run: cargo clippy --features=prometheus-client
       - run: cargo clippy --features=opentelemetry
 
-      # Build the packages
-      - run: cargo build
-      - run: cargo build --features=custom-objective-percentile,custom-objective-latency
-
       # Run the tests with each of the different metrics libraries
-      - run: cargo test --features=prometheus-exporter
-      - run: cargo test --no-default-features --features=prometheus-exporter,metrics --tests
-      - run: cargo test --no-default-features --features=prometheus-exporter,prometheus --tests
-      - run: cargo test --no-default-features --features=prometheus-exporter,prometheus-client --tests
+      - run: cargo test --features=prometheus-exporter,metrics
+      - run: cargo test --features=prometheus-exporter,prometheus --tests
+      - run: cargo test --features=prometheus-exporter,prometheus-client --tests
+      # The tests using opentelemetry are currently failing because of this issue:
+      # https://github.com/open-telemetry/opentelemetry-rust/issues/1070
+      # We should remove the continue-on-error once that is fixed
+      - run: cargo test --features=prometheus-exporter,opentelemetry
+        continue-on-error: true
+
+      # Build the crate using the other optional features
+      - run: cargo build --features=metrics,custom-objective-percentile,custom-objective-latency
 
       # Compile the examples
       - run: cargo build --package example-axum

CHANGELOG.md

@@ -17,9 +17,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- Users must configure the metrics library they want to use autometrics with
+- Metrics library feature flags are now mutually exclusive (previously, `autometrics` would only
+  produce metrics using a single metrics library if multiple feature flags were enabled, using
+  a prioritization order defined internally)
 - `GetLabels` trait (publicly exported but meant for internal use) changed the signature
   of its function to accomodate the new `ResultLabels` macro. This change is not significant
   if you never imported `autometrics::__private` manually (#61)
+- When using the `opentelemetry` together with the `prometheus-exporter`, it will no longer
+  use the default registry provided by the `prometheus` crate. It will instead use a new registry
+- The `prometheus-exporter`'s `encode_global_metrics` feature now returns an error enum
+  defined by `autometrics` as opposed to directly returning the `prometheus::Error` type
 - Updated `opentelemetry` dependencies to v0.19. This means that users using autometrics
   with `opentelemetry` but not using the `prometheus-exporter` must update the `opentelemetry`
   to use v0.19.
@@ -29,6 +37,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Removed
 
+- `opentelemetry` is no longer used by default
 - `GetLabelsForResult` trait (publicly exported but meant for internal use) was removed
   to accomodate the new `ResultLabels` macro. This change is not significant
   if you never imported `autometrics::__private` manually (#61)

README.md

@@ -63,7 +63,7 @@ See [Why Autometrics?](https://github.com/autometrics-dev#4-why-autometrics) for
 
 1. Add `autometrics` to your project:
     ```sh
-    cargo add autometrics --features=prometheus-exporter
+    cargo add autometrics --features=prometheus,prometheus-exporter
     ```
 2. Instrument your functions with the [`#[autometrics]`](https://docs.rs/autometrics/latest/autometrics/attr.autometrics.html) macro
 

autometrics/Cargo.toml

@@ -13,7 +13,6 @@ categories = { workspace = true }
 readme = "README.md"
 
 [features]
-default = ["opentelemetry"]
 metrics = ["dep:metrics"]
 opentelemetry = ["opentelemetry_api"]
 prometheus = ["dep:prometheus"]
@@ -22,7 +21,8 @@ prometheus-exporter = [
   "metrics-exporter-prometheus",
   "opentelemetry-prometheus",
   "opentelemetry_sdk",
-  "prometheus"
+  "dep:prometheus",
+  "thiserror"
 ]
 custom-objective-percentile = []
 custom-objective-latency = []
@@ -43,6 +43,7 @@ metrics-exporter-prometheus = { version = "0.12", default-features = false, opti
 opentelemetry-prometheus = { version = "0.12.0", optional = true }
 opentelemetry_sdk = { version = "0.19", default-features = false, features = ["metrics"], optional = true }
 prometheus = { version = "0.13", default-features = false, optional = true }
+thiserror = { version = "1", optional = true }
 
 # Used for prometheus-client feature
 prometheus-client = { version = "0.21.1", optional = true }

autometrics/README.md

@@ -115,12 +115,13 @@ fn main() {
 
 #### Metrics Libraries
 
-Configure the crate that autometrics will use to produce metrics by using one of the following feature flags:
+**Required:** Configure the crate that autometrics will use to produce metrics by using one of the following feature flags:
 
 > **Note**
 >
 > If you are **not** using the `prometheus-exporter`, you must ensure that you are using the exact same version of the metrics library as `autometrics` (and it must come from `crates.io` rather than git or another source). If not, the autometrics metrics will not appear in your exported metrics.
 
-- `opentelemetry` (enabled by default) - use the [opentelemetry](https://crates.io/crates/opentelemetry) crate for producing metrics.
+- `opentelemetry`  - use the [opentelemetry](https://crates.io/crates/opentelemetry) crate for producing metrics.
 - `metrics` - use the [metrics](https://crates.io/crates/metrics) crate for producing metrics
 - `prometheus` - use the [prometheus](https://crates.io/crates/prometheus) crate for producing metrics
+- `prometheus-client` - use the official [prometheus-client](https://crates.io/crates/prometheus-client) crate for producing metrics

autometrics/src/prometheus_exporter.rs

@@ -1,48 +1,94 @@
-use crate::HISTOGRAM_BUCKETS;
 #[cfg(feature = "metrics")]
 use metrics_exporter_prometheus::{PrometheusBuilder, PrometheusHandle};
 use once_cell::sync::Lazy;
+#[cfg(feature = "opentelemetry")]
 use opentelemetry_prometheus::{exporter, PrometheusExporter};
+#[cfg(feature = "opentelemetry")]
 use opentelemetry_sdk::export::metrics::aggregation;
+#[cfg(feature = "opentelemetry")]
 use opentelemetry_sdk::metrics::{controllers, processors, selectors};
-use prometheus::{default_registry, Error, TextEncoder};
+#[cfg(any(feature = "opentelemetry", feature = "prometheus"))]
+use prometheus::TextEncoder;
+use thiserror::Error;
 
-static GLOBAL_EXPORTER: Lazy<GlobalPrometheus> = Lazy::new(initialize_metrics_exporter);
+#[cfg(not(any(
+    feature = "metrics",
+    feature = "opentelemetry",
+    feature = "prometheus",
+    feature = "prometheus-client"
+)))]
+compile_error!("At least one of the metrics, opentelemetry, prometheus, or prometheus-client features must be enabled in order to use the prometheus-exporter");
+
+#[derive(Debug, Error)]
+pub enum EncodingError {
+    #[cfg(any(feature = "prometheus", feature = "opentelemetry"))]
+    #[error(transparent)]
+    Prometheus(#[from] prometheus::Error),
+    #[cfg(feature = "prometheus-client")]
+    #[error(transparent)]
+    Format(#[from] std::fmt::Error),
+}
+
+static GLOBAL_EXPORTER: Lazy<GlobalPrometheus> = Lazy::new(|| GlobalPrometheus {
+    #[cfg(feature = "metrics")]
+    metrics_exporter: PrometheusBuilder::new()
+        .set_buckets(&crate::HISTOGRAM_BUCKETS)
+        .expect("Failed to set histogram buckets")
+        .install_recorder()
+        .expect("Failed to install recorder"),
+
+    #[cfg(feature = "opentelemetry")]
+    opentelemetry_exporter: exporter(
+        controllers::basic(processors::factory(
+            selectors::simple::histogram(crate::HISTOGRAM_BUCKETS),
+            aggregation::cumulative_temporality_selector(),
+        ))
+        .build(),
+    )
+    .init(),
+});
 
 #[derive(Clone)]
 #[doc(hidden)]
 pub struct GlobalPrometheus {
-    exporter: PrometheusExporter,
+    #[cfg(feature = "opentelemetry")]
+    opentelemetry_exporter: PrometheusExporter,
     #[cfg(feature = "metrics")]
-    handle: PrometheusHandle,
+    metrics_exporter: PrometheusHandle,
 }
 
 impl GlobalPrometheus {
-    fn encode_metrics(&self) -> Result<String, Error> {
-        let metric_families = self.exporter.registry().gather();
-        let encoder = TextEncoder::new();
-        #[allow(unused_mut)]
-        let mut output = encoder.encode_to_string(&metric_families)?;
+    fn encode_metrics(&self) -> Result<String, EncodingError> {
+        let mut output = String::new();
 
         #[cfg(feature = "metrics")]
         {
+            output.push_str(&self.metrics_exporter.render());
             output.push('\n');
-            output.push_str(&self.handle.render());
         }
 
-        #[cfg(feature = "prometheus-client")]
+        #[cfg(feature = "opentelemetry")]
         {
+            let metric_families = self.opentelemetry_exporter.registry().gather();
+            let encoder = TextEncoder::new();
+            encoder.encode_utf8(&metric_families, &mut output)?;
             output.push('\n');
+        }
+
+        #[cfg(feature = "prometheus")]
+        {
+            let metric_families = prometheus::default_registry().gather();
+            let encoder = TextEncoder::new();
+            encoder.encode_utf8(&metric_families, &mut output)?;
+            output.push('\n');
+        }
+
+        #[cfg(feature = "prometheus-client")]
+        {
             prometheus_client::encoding::text::encode(
                 &mut output,
                 &crate::tracker::prometheus_client::REGISTRY,
-            )
-            .map_err(|err| {
-                Error::Msg(format!(
-                    "Failed to encode prometheus-client metrics: {}",
-                    err
-                ))
-            })?;
+            )?;
         }
 
         Ok(output)
@@ -84,30 +130,6 @@ pub fn global_metrics_exporter() -> GlobalPrometheus {
 ///   }
 /// }
 /// ```
-pub fn encode_global_metrics() -> Result<String, Error> {
+pub fn encode_global_metrics() -> Result<String, EncodingError> {
     GLOBAL_EXPORTER.encode_metrics()
 }
-
-fn initialize_metrics_exporter() -> GlobalPrometheus {
-    let controller = controllers::basic(processors::factory(
-        selectors::simple::histogram(HISTOGRAM_BUCKETS),
-        aggregation::cumulative_temporality_selector(),
-    ))
-    .build();
-
-    // Use the prometheus crate's default registry so it still works with custom
-    // metrics defined through the prometheus crate
-    let registry = default_registry().clone();
-    let prometheus_exporter = exporter(controller).with_registry(registry).init();
-
-    GlobalPrometheus {
-        exporter: prometheus_exporter,
-
-        #[cfg(feature = "metrics")]
-        handle: PrometheusBuilder::new()
-            .set_buckets(&HISTOGRAM_BUCKETS)
-            .expect("Failed to set histogram buckets")
-            .install_recorder()
-            .expect("Failed to install recorder"),
-    }
-}

autometrics/src/tracker/mod.rs

@@ -9,36 +9,89 @@ mod prometheus;
 #[cfg(feature = "prometheus-client")]
 pub(crate) mod prometheus_client;
 
-// Priority if multiple features are enabled:
-// 1. prometheus
-// 2. prometheus-client
-// 3. metrics
-// 4. opentelemetry (default)
-
-// By default, use the opentelemetry crate
-#[cfg(all(
-    feature = "opentelemetry",
-    not(any(
-        feature = "metrics",
-        feature = "prometheus",
-        feature = "prometheus-client"
-    ))
-))]
-pub use self::opentelemetry::OpenTelemetryTracker as AutometricsTracker;
+#[cfg(feature = "metrics")]
+pub use self::metrics::MetricsTracker;
+#[cfg(feature = "opentelemetry")]
+pub use self::opentelemetry::OpenTelemetryTracker;
+#[cfg(feature = "prometheus")]
+pub use self::prometheus::PrometheusTracker;
+#[cfg(feature = "prometheus-client")]
+pub use self::prometheus_client::PrometheusClientTracker;
 
-// But use one of the other crates if any of those features are enabled
-#[cfg(all(
-    feature = "metrics",
-    not(any(feature = "prometheus", feature = "prometheus-client"))
+#[cfg(any(
+    all(
+        feature = "metrics",
+        any(
+            feature = "opentelemetry",
+            feature = "prometheus",
+            feature = "prometheus-client"
+        )
+    ),
+    all(
+        feature = "opentelemetry",
+        any(feature = "prometheus", feature = "prometheus-client")
+    ),
+    all(feature = "prometheus", feature = "prometheus-client")
 ))]
-pub use self::metrics::MetricsTracker as AutometricsTracker;
-#[cfg(feature = "prometheus")]
-pub use self::prometheus::PrometheusTracker as AutometricsTracker;
-#[cfg(all(feature = "prometheus-client", not(feature = "prometheus")))]
-pub use self::prometheus_client::PrometheusClientTracker as AutometricsTracker;
+compile_error!("Only one of the metrics, opentelemetry, prometheus, or prometheus-client features can be enabled at a time");
 
 pub trait TrackMetrics {
     fn set_build_info(build_info_labels: &BuildInfoLabels);
     fn start(gauge_labels: Option<&GaugeLabels>) -> Self;
     fn finish(self, counter_labels: &CounterLabels, histogram_labels: &HistogramLabels);
 }
+
+pub struct AutometricsTracker {
+    #[cfg(feature = "metrics")]
+    metrics_tracker: MetricsTracker,
+    #[cfg(feature = "opentelemetry")]
+    opentelemetry_tracker: OpenTelemetryTracker,
+    #[cfg(feature = "prometheus")]
+    prometheus_tracker: PrometheusTracker,
+    #[cfg(feature = "prometheus-client")]
+    prometheus_client_tracker: PrometheusClientTracker,
+}
+
+impl TrackMetrics for AutometricsTracker {
+    #[allow(unused_variables)]
+    fn set_build_info(build_info_labels: &BuildInfoLabels) {
+        #[cfg(feature = "metrics")]
+        MetricsTracker::set_build_info(build_info_labels);
+        #[cfg(feature = "opentelemetry")]
+        OpenTelemetryTracker::set_build_info(build_info_labels);
+        #[cfg(feature = "prometheus")]
+        PrometheusTracker::set_build_info(build_info_labels);
+        #[cfg(feature = "prometheus-client")]
+        PrometheusClientTracker::set_build_info(build_info_labels);
+    }
+
+    #[allow(unused_variables)]
+    fn start(gauge_labels: Option<&GaugeLabels>) -> Self {
+        Self {
+            #[cfg(feature = "metrics")]
+            metrics_tracker: MetricsTracker::start(gauge_labels),
+            #[cfg(feature = "opentelemetry")]
+            opentelemetry_tracker: OpenTelemetryTracker::start(gauge_labels),
+            #[cfg(feature = "prometheus")]
+            prometheus_tracker: PrometheusTracker::start(gauge_labels),
+            #[cfg(feature = "prometheus-client")]
+            prometheus_client_tracker: PrometheusClientTracker::start(gauge_labels),
+        }
+    }
+
+    #[allow(unused_variables)]
+    fn finish(self, counter_labels: &CounterLabels, histogram_labels: &HistogramLabels) {
+        #[cfg(feature = "metrics")]
+        self.metrics_tracker
+            .finish(counter_labels, histogram_labels);
+        #[cfg(feature = "opentelemetry")]
+        self.opentelemetry_tracker
+            .finish(counter_labels, histogram_labels);
+        #[cfg(feature = "prometheus")]
+        self.prometheus_tracker
+            .finish(counter_labels, histogram_labels);
+        #[cfg(feature = "prometheus-client")]
+        self.prometheus_client_tracker
+            .finish(counter_labels, histogram_labels);
+    }
+}

examples/axum/Cargo.toml

@@ -5,7 +5,7 @@ publish = false
 edition = "2021"
 
 [dependencies]
-autometrics = { path = "../../autometrics", features = ["prometheus-exporter"] }
+autometrics = { path = "../../autometrics", features = ["prometheus", "prometheus-exporter"] }
 autometrics-example-util = { path = "../util" }
 axum = { version = "0.6", features = ["json"] }
 rand = "0.8"

examples/full-api/Cargo.toml

@@ -5,7 +5,7 @@ publish = false
 edition = "2021"
 
 [dependencies]
-autometrics = { path = "../../autometrics", features = ["prometheus-exporter"] }
+autometrics = { path = "../../autometrics", features = ["prometheus", "prometheus-exporter"] }
 autometrics-example-util = { path = "../util" }
 axum = { version = "0.6", features = ["json"] }
 rand = "0.8"