Add serde style encoding for Summary

Signed-off-by: Palash Nigam <npalash25@gmail.com>

src/encoding.rs

@@ -131,6 +131,21 @@ impl<'a, 'b> MetricEncoder<'a, 'b> {
         )
     }
 
+    /// Encode a summary.
+    pub fn encode_summary<S: EncodeLabelSet>(
+        &mut self,
+        sum: f64,
+        count: u64,
+        quantiles: &[(f64, f64)],
+    ) -> Result<(), std::fmt::Error> {
+        for_both_mut!(
+            self,
+            MetricEncoderInner,
+            e,
+            e.encode_summary(sum, count, quantiles)
+        )
+    }
+
     /// Encode a metric family.
     pub fn encode_family<'c, 'd, S: EncodeLabelSet>(
         &'c mut self,

src/encoding/protobuf.rs

@@ -99,6 +99,7 @@ impl From<MetricType> for openmetrics_data_model::MetricType {
             MetricType::Counter => openmetrics_data_model::MetricType::Counter,
             MetricType::Gauge => openmetrics_data_model::MetricType::Gauge,
             MetricType::Histogram => openmetrics_data_model::MetricType::Histogram,
+            MetricType::Summary => openmetrics_data_model::MetricType::Summary,
             MetricType::Info => openmetrics_data_model::MetricType::Info,
             MetricType::Unknown => openmetrics_data_model::MetricType::Unknown,
         }
@@ -247,6 +248,44 @@ impl<'a> MetricEncoder<'a> {
 
         Ok(())
     }
+
+    pub fn encode_summary<S: EncodeLabelSet>(
+        &mut self,
+        sum: f64,
+        count: u64,
+        quantile: &[(f64, f64)],
+    ) -> Result<(), std::fmt::Error> {
+        let quantiles = quantiles
+            .iter()
+            .enumerate()
+            .map(|(_, (quantile, value))| {
+                Ok(openmetrics_data_model::summary_value::Quantile {
+                    quantile: *quantile,
+                    value: *value,
+                })
+            })
+            .collect::<Result<Vec<_>, std::fmt::Error>>()?;
+
+        self.family.push(openmetrics_data_model::Metric {
+            labels: self.labels.clone(),
+            metric_points: vec![openmetrics_data_model::MetricPoint {
+                value: Some(openmetrics_data_model::metric_point::Value::SummaryValue(
+                    openmetrics_data_model::SummaryValue {
+                        count,
+                        created: None,
+                        quantiles,
+                        sum: Some(openmetrics_data_model::summary_value::Sum::DoubleValue(
+                            sum,
+                        )),
+                    },
+                )),
+                ..Default::default()
+            }],
+        });
+
+        Ok(())
+    }
+
 }
 
 impl<S: EncodeLabelSet, V: EncodeExemplarValue> TryFrom<&Exemplar<S, V>>
@@ -403,6 +442,7 @@ mod tests {
     use crate::metrics::family::Family;
     use crate::metrics::gauge::Gauge;
     use crate::metrics::histogram::{exponential_buckets, Histogram};
+    use crate::metrics::summary::Summary;
     use crate::metrics::info::Info;
     use crate::registry::Unit;
     use std::borrow::Cow;
@@ -643,6 +683,39 @@ mod tests {
         }
     }
 
+    #[test]
+    fn encode_summary() {
+        let mut registry = Registry::default();
+        let summary = Summary::new(5, 10, vec![0.5, 0.9, 0.99], 0.01);
+        registry.register("my_summary", "My summary", summary.clone());
+        summary.observe(1.0);
+
+        let metric_set = encode(&registry).unwrap();
+
+        let family = metric_set.metric_families.first().unwrap();
+        assert_eq!("my_summary", family.name);
+        assert_eq!("My summary.", family.help);
+
+        assert_eq!(
+            openmetrics_data_model::MetricType::Summary as i32,
+            extract_metric_type(&metric_set)
+        );
+
+        match extract_metric_point_value(metric_set) {
+            openmetrics_data_model::metric_point::Value::SummaryValue(value) => {
+                assert_eq!(
+                    Some(openmetrics_data_model::summary_value::Sum::DoubleValue(
+                        1.0
+                    )),
+                    value.sum
+                );
+                assert_eq!(1, value.count);
+                assert_eq!(11, value.quantile.len());
+            }
+            _ => panic!("wrong value type"),
+        }
+    }
+
     #[test]
     fn encode_histogram() {
         let mut registry = Registry::default();

src/encoding/text.rs

@@ -211,6 +211,40 @@ impl<'a, 'b> MetricEncoder<'a, 'b> {
         })
     }
 
+    pub fn encode_summary<S: EncodeLabelSet>(
+        &mut self,
+        sum: f64,
+        count: u64,
+        quantiles: &[(f64, f64)],
+    ) -> Result<(), std::fmt::Error> {
+        self.write_name_and_unit()?;
+        self.write_suffix("sum")?;
+        self.encode_labels::<()>(None)?;
+        self.writer.write_str(" ")?;
+        self.writer.write_str(dtoa::Buffer::new().format(sum))?;
+        self.newline()?;
+
+        self.write_name_and_unit()?;
+        self.write_suffix("count")?;
+        self.encode_labels::<()>(None)?;
+        self.writer.write_str(" ")?;
+        self.writer.write_str(itoa::Buffer::new().format(count))?;
+        self.newline()?;
+
+        for (_, (quantile, result)) in quantiles.iter().enumerate() {
+            self.write_name_and_unit()?;
+            self.encode_labels(Some(&[("quantile", *quantile)]))?;
+
+            self.writer.write_str(" ")?;
+            self.writer
+                .write_str(result.to_string().as_str())?;
+
+            self.newline()?;
+        }
+
+        Ok(())
+    }
+
     pub fn encode_histogram<S: EncodeLabelSet>(
         &mut self,
         sum: f64,
@@ -511,6 +545,7 @@ mod tests {
     use crate::metrics::family::Family;
     use crate::metrics::gauge::Gauge;
     use crate::metrics::histogram::{exponential_buckets, Histogram};
+    use crate::metrics::summary::Summary;
     use crate::metrics::info::Info;
     use crate::metrics::{counter::Counter, exemplar::CounterWithExemplar};
     use pyo3::{prelude::*, types::PyModule};
@@ -732,8 +767,7 @@ mod tests {
         summary.observe(0.20);
         summary.observe(0.30);
 
-        let mut encoded = Vec::new();
-
+        let mut encoded = String::new();
         encode(&mut encoded, &registry).unwrap();
 
         let expected = "# HELP my_summary My summary.\n".to_owned()
@@ -744,9 +778,9 @@ mod tests {
             + "my_summary{quantile=\"0.9\"} 0.3\n"
             + "my_summary{quantile=\"0.99\"} 0.3\n"
             + "# EOF\n";
-        assert_eq!(expected, String::from_utf8(encoded.clone()).unwrap());
+        assert_eq!(expected, encoded);
 
-        parse_with_python_client(String::from_utf8(encoded).unwrap());
+        parse_with_python_client(encoded);
     }
 
     fn parse_with_python_client(input: String) {

src/metrics.rs

@@ -38,6 +38,7 @@ impl MetricType {
             MetricType::Counter => "counter",
             MetricType::Gauge => "gauge",
             MetricType::Histogram => "histogram",
+            MetricType::Summary => "summary",
             MetricType::Info => "info",
             MetricType::Unknown => "unknown",
         }

src/metrics/summary.rs

@@ -2,6 +2,8 @@
 //!
 //! See [`Summary`] for details.
 
+use crate::encoding::{EncodeMetric, MetricEncoder};
+
 use super::{MetricType, TypedMetric};
 //use owning_ref::OwningRef;
 //use std::iter::{self, once};
@@ -126,6 +128,18 @@ impl TypedMetric for Summary {
     const TYPE: MetricType = MetricType::Summary;
 }
 
+impl EncodeMetric for Summary {
+    fn encode(&self, mut encoder: MetricEncoder) -> Result<(), std::fmt::Error> {
+        let (sum, count, quantiles) = self.get();
+        encoder.encode_summary::<()>(sum, count, &quantiles)
+    }
+
+    fn metric_type(&self) -> MetricType {
+        Self::TYPE
+    }
+}
+
+
 #[cfg(test)]
 mod tests {
     use super::*;