src/registry: Use dynamic dispatch and remove type parameter M

CHANGELOG.md

@@ -11,6 +11,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- Always use dynamic dispatch on Registry, i.e. remove generic type parameter `M` from `Registry`.
+
 - Move`Encode` trait from `prometheus_client::encoding::text` to `prometheus_client::encoding`. See [PR 83].
 
 [PR 83]: https://github.com/prometheus/client_rust/pull/83

examples/actix-web.rs

@@ -7,13 +7,13 @@ use prometheus_client::metrics::counter::Counter;
 use prometheus_client::metrics::family::Family;
 use prometheus_client::registry::Registry;
 
-#[derive(Clone, Hash, PartialEq, Eq, Encode)]
+#[derive(Clone, Debug, Hash, PartialEq, Eq, Encode)]
 pub enum Method {
     Get,
     Post,
 }
 
-#[derive(Clone, Hash, PartialEq, Eq, Encode)]
+#[derive(Clone, Debug, Hash, PartialEq, Eq, Encode)]
 pub struct MethodLabels {
     pub method: Method,
 }
@@ -55,11 +55,9 @@ async fn main() -> std::io::Result<()> {
     let mut state = AppState {
         registry: Registry::default(),
     };
-    state.registry.register(
-        "requests",
-        "Count of requests",
-        Box::new(metrics.requests.clone()),
-    );
+    state
+        .registry
+        .register("requests", "Count of requests", metrics.requests.clone());
     let state = web::Data::new(Mutex::new(state));
 
     HttpServer::new(move || {

examples/custom-metric.rs

@@ -7,6 +7,7 @@ use prometheus_client::registry::Registry;
 /// Related to the concept of "Custom Collectors" in other implementations.
 ///
 /// [`MyCustomMetric`] generates and encodes a random number on each scrape.
+#[derive(Debug)]
 struct MyCustomMetric {}
 
 impl EncodeMetric for MyCustomMetric {

examples/tide.rs

@@ -44,21 +44,21 @@ async fn main() -> std::result::Result<(), std::io::Error> {
     Ok(())
 }
 
-#[derive(Clone, Hash, PartialEq, Eq, Encode)]
+#[derive(Clone, Debug, Hash, PartialEq, Eq, Encode)]
 struct Labels {
     method: Method,
     path: String,
 }
 
-#[derive(Clone, Hash, PartialEq, Eq, Encode)]
+#[derive(Clone, Debug, Hash, PartialEq, Eq, Encode)]
 enum Method {
     Get,
     Put,
 }
 
 #[derive(Clone)]
 struct State {
-    registry: Arc<Registry<Family<Labels, Counter>>>,
+    registry: Arc<Registry>,
 }
 
 #[derive(Default)]

src/encoding/proto.rs

@@ -47,7 +47,7 @@ pub use prometheus_client_derive_encode::*;
 
 /// Encode the metrics registered with the provided [`Registry`] into MetricSet
 /// using the OpenMetrics protobuf format.
-pub fn encode<M>(registry: &Registry<M>) -> openmetrics_data_model::MetricSet
+pub fn encode<M>(registry: &Registry) -> openmetrics_data_model::MetricSet
 where
     M: EncodeMetric,
 {
@@ -57,7 +57,8 @@ where
         let mut family = openmetrics_data_model::MetricFamily {
             name: desc.name().to_string(),
             r#type: {
-                let metric_type: openmetrics_data_model::MetricType = metric.metric_type().into();
+                let metric_type: openmetrics_data_model::MetricType =
+                    EncodeMetric::metric_type(metric.as_ref()).into();
                 metric_type as i32
             },
             unit: if let Some(unit) = desc.unit() {
@@ -71,7 +72,7 @@ where
 
         let mut labels = vec![];
         desc.labels().encode(&mut labels);
-        metric.encode(labels, &mut family.metrics);
+        EncodeMetric::encode(metric.as_ref(), labels, &mut family.metrics);
 
         metric_set.metric_families.push(family);
     }
@@ -118,11 +119,6 @@ impl EncodeMetric for Box<dyn EncodeMetric> {
     }
 }
 
-/// Trait combining [`EncodeMetric`] and [`Send`].
-pub trait SendEncodeMetric: EncodeMetric + Send {}
-
-impl<T: EncodeMetric + Send> SendEncodeMetric for T {}
-
 /// Trait to implement its label encoding in the OpenMetrics protobuf format.
 pub trait EncodeLabels {
     /// Encode the given instance into Labels in the OpenMetrics protobuf

src/encoding/text.rs

@@ -40,10 +40,9 @@ use std::ops::Deref;
 
 /// Encode the metrics registered with the provided [`Registry`] into the
 /// provided [`Write`]r using the OpenMetrics text format.
-pub fn encode<W, M>(writer: &mut W, registry: &Registry<M>) -> Result<(), std::io::Error>
+pub fn encode<W>(writer: &mut W, registry: &Registry) -> Result<(), std::io::Error>
 where
     W: Write,
-    M: EncodeMetric,
 {
     for (desc, metric) in registry.iter() {
         writer.write_all(b"# HELP ")?;
@@ -63,7 +62,7 @@ where
             unit.encode(writer)?;
         }
         writer.write_all(b" ")?;
-        metric.metric_type().encode(writer)?;
+        EncodeMetric::metric_type(metric.as_ref()).encode(writer)?;
         writer.write_all(b"\n")?;
 
         if let Some(unit) = desc.unit() {
@@ -84,7 +83,7 @@ where
             labels: None,
         };
 
-        metric.encode(encoder)?;
+        EncodeMetric::encode(metric.as_ref(), encoder)?;
     }
 
     writer.write_all(b"# EOF\n")?;
@@ -402,21 +401,6 @@ impl EncodeMetric for Box<dyn EncodeMetric> {
     }
 }
 
-/// Trait combining [`EncodeMetric`], [`Send`] and [`Sync`].
-pub trait SendSyncEncodeMetric: EncodeMetric + Send + Sync {}
-
-impl<T: EncodeMetric + Send + Sync> SendSyncEncodeMetric for T {}
-
-impl EncodeMetric for Box<dyn SendSyncEncodeMetric> {
-    fn encode(&self, encoder: Encoder) -> Result<(), std::io::Error> {
-        self.deref().encode(encoder)
-    }
-
-    fn metric_type(&self) -> MetricType {
-        self.deref().metric_type()
-    }
-}
-
 /////////////////////////////////////////////////////////////////////////////////
 // Counter
 

src/lib.rs

@@ -30,15 +30,15 @@
 //! //
 //! // You could as well use `(String, String)` to represent a label set,
 //! // instead of the custom type below.
-//! #[derive(Clone, Hash, PartialEq, Eq, Encode)]
+//! #[derive(Clone, Debug, Hash, PartialEq, Eq, Encode)]
 //! struct Labels {
 //!   // Use your own enum types to represent label values.
 //!   method: Method,
 //!   // Or just a plain string.
 //!   path: String,
 //! };
 //!
-//! #[derive(Clone, Hash, PartialEq, Eq, Encode)]
+//! #[derive(Clone, Debug, Hash, PartialEq, Eq, Encode)]
 //! enum Method {
 //!   GET,
 //!   PUT,
@@ -54,7 +54,7 @@
 //!   "http_requests",
 //!   // And the metric help text.
 //!   "Number of HTTP requests received",
-//!   Box::new(http_requests.clone()),
+//!   http_requests.clone(),
 //! );
 //!
 //! // Somewhere in your business logic record a single HTTP GET request.

src/metrics/family.rs

@@ -65,12 +65,12 @@ use std::sync::Arc;
 /// # use std::io::Write;
 /// #
 /// # let mut registry = Registry::default();
-/// #[derive(Clone, Hash, PartialEq, Eq, Encode)]
+/// #[derive(Clone, Debug, Hash, PartialEq, Eq, Encode)]
 /// struct Labels {
 ///   method: Method,
 /// };
 ///
-/// #[derive(Clone, Hash, PartialEq, Eq, Encode)]
+/// #[derive(Clone, Debug, Hash, PartialEq, Eq, Encode)]
 /// enum Method {
 ///   GET,
 ///   PUT,
@@ -97,7 +97,6 @@ use std::sync::Arc;
 /// # assert_eq!(expected, String::from_utf8(buffer).unwrap());
 /// ```
 // TODO: Consider exposing hash algorithm.
-#[derive(Debug)]
 pub struct Family<S, M, C = fn() -> M> {
     metrics: Arc<RwLock<HashMap<S, M>>>,
     /// Function that when called constructs a new metric.
@@ -111,6 +110,14 @@ pub struct Family<S, M, C = fn() -> M> {
     constructor: C,
 }
 
+impl<S: std::fmt::Debug, M: std::fmt::Debug, C> std::fmt::Debug for Family<S, M, C> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Family")
+            .field("metrics", &self.metrics)
+            .finish()
+    }
+}
+
 /// A constructor for creating new metrics in a [`Family`] when calling
 /// [`Family::get_or_create`]. Such constructor is provided via
 /// [`Family::new_with_constructor`].