feat(encoding)!: EncodeMetric does not consume MetricEncoder

see prometheus#135.

this adjusts the parameter of `encode()` so that it only mutably borrows
the encoder.

Signed-off-by: katelyn martin <[email protected]>

examples/custom-metric.rs

@@ -11,7 +11,7 @@ use prometheus_client::registry::Registry;
 struct MyCustomMetric {}
 
 impl EncodeMetric for MyCustomMetric {
-    fn encode(&self, mut encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error> {
         // This method is called on each Prometheus server scrape. Allowing you
         // to execute whatever logic is needed to generate and encode your
         // custom metric.

src/encoding.rs

@@ -43,7 +43,7 @@ macro_rules! for_both {
 pub trait EncodeMetric {
     /// Encode the given instance in the OpenMetrics text encoding.
     // TODO: Lifetimes on MetricEncoder needed?
-    fn encode(&self, encoder: MetricEncoder) -> Result<(), std::fmt::Error>;
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error>;
 
     /// The OpenMetrics metric type of the instance.
     // One can not use [`TypedMetric`] directly, as associated constants are not
@@ -52,7 +52,7 @@ pub trait EncodeMetric {
 }
 
 impl EncodeMetric for Box<dyn EncodeMetric> {
-    fn encode(&self, encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error> {
         self.deref().encode(encoder)
     }
 

src/encoding/text.rs

@@ -1080,13 +1080,13 @@ mod tests {
                 mut encoder: crate::encoding::DescriptorEncoder,
             ) -> Result<(), std::fmt::Error> {
                 let counter = crate::metrics::counter::ConstCounter::new(42u64);
-                let metric_encoder = encoder.encode_descriptor(
+                let mut metric_encoder = encoder.encode_descriptor(
                     &self.name,
                     "some help",
                     None,
                     counter.metric_type(),
                 )?;
-                counter.encode(metric_encoder)?;
+                counter.encode(&mut metric_encoder)?;
                 Ok(())
             }
         }

src/metrics/counter.rs

@@ -203,7 +203,7 @@ where
     N: crate::encoding::EncodeCounterValue,
     A: Atomic<N>,
 {
-    fn encode(&self, mut encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error> {
         encoder.encode_counter::<NoLabelSet, _, u64>(&self.get(), None)
     }
 
@@ -235,7 +235,7 @@ impl<N> EncodeMetric for ConstCounter<N>
 where
     N: crate::encoding::EncodeCounterValue,
 {
-    fn encode(&self, mut encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error> {
         encoder.encode_counter::<NoLabelSet, _, u64>(&self.value, None)
     }
 

src/metrics/exemplar.rs

@@ -155,7 +155,7 @@ where
     N: EncodeCounterValue + EncodeExemplarValue + Clone,
     A: counter::Atomic<N>,
 {
-    fn encode(&self, mut encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error> {
         let (value, exemplar) = self.get();
         encoder.encode_counter(&value, exemplar.as_ref())
     }
@@ -267,7 +267,7 @@ impl<S> HistogramWithExemplars<S> {
 }
 
 impl<S: EncodeLabelSet> EncodeMetric for HistogramWithExemplars<S> {
-    fn encode(&self, mut encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error> {
         let inner = self.inner();
         let (sum, count, buckets) = inner.histogram.get();
         encoder.encode_histogram(sum, count, &buckets, Some(&inner.exemplars))

src/metrics/family.rs

@@ -312,11 +312,11 @@ where
     M: EncodeMetric + TypedMetric,
     C: MetricConstructor<M>,
 {
-    fn encode(&self, mut encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error> {
         let guard = self.read();
         for (label_set, m) in guard.iter() {
-            let encoder = encoder.encode_family(label_set)?;
-            m.encode(encoder)?;
+            let mut encoder = encoder.encode_family(label_set)?;
+            m.encode(&mut encoder)?;
         }
         Ok(())
     }

src/metrics/gauge.rs

@@ -346,7 +346,7 @@ where
     N: EncodeGaugeValue,
     A: Atomic<N>,
 {
-    fn encode(&self, mut encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error> {
         encoder.encode_gauge(&self.get())
     }
     fn metric_type(&self) -> MetricType {
@@ -377,7 +377,7 @@ impl<N> EncodeMetric for ConstGauge<N>
 where
     N: EncodeGaugeValue,
 {
-    fn encode(&self, mut encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error> {
         encoder.encode_gauge(&self.value)
     }
 

src/metrics/histogram.rs

@@ -131,7 +131,7 @@ pub fn linear_buckets(start: f64, width: f64, length: u16) -> impl Iterator<Item
 }
 
 impl EncodeMetric for Histogram {
-    fn encode(&self, mut encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error> {
         let (sum, count, buckets) = self.get();
         encoder.encode_histogram::<NoLabelSet>(sum, count, &buckets, None)
     }

src/metrics/info.rs

@@ -33,7 +33,7 @@ impl<S> EncodeMetric for Info<S>
 where
     S: Clone + std::hash::Hash + Eq + EncodeLabelSet,
 {
-    fn encode(&self, mut encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+    fn encode(&self, encoder: &mut MetricEncoder) -> Result<(), std::fmt::Error> {
         encoder.encode_info(&self.0)
     }
 

src/registry.rs

@@ -290,13 +290,13 @@ impl Registry {
         for (descriptor, metric) in self.metrics.iter() {
             let mut descriptor_encoder =
                 encoder.with_prefix_and_labels(self.prefix.as_ref(), &self.labels);
-            let metric_encoder = descriptor_encoder.encode_descriptor(
+            let mut metric_encoder = descriptor_encoder.encode_descriptor(
                 &descriptor.name,
                 &descriptor.help,
                 descriptor.unit.as_ref(),
                 EncodeMetric::metric_type(metric.as_ref()),
             )?;
-            metric.encode(metric_encoder)?;
+            metric.encode(&mut metric_encoder)?;
         }
 
         for collector in self.collectors.iter() {