protobuf: move from OpenMetrics to Prometheus proto (#298)

* dependencies: update prost to 0.14

Signed-off-by: John Howard <john.howard@solo.io>

* protobuf: allow compiling without `protoc`

Our goal is to have our builds compile without external dependencies.
`protox` helps achieve this.

Signed-off-by: John Howard <john.howard@solo.io>

* protobuf: move from openmetrics to protobuf

Signed-off-by: John Howard <john.howard@solo.io>

* Update changelog

Signed-off-by: John Howard <john.howard@solo.io>

* Bring back legacy proto

Signed-off-by: John Howard <john.howard@solo.io>

* Retain old 'protobuf' feature, make explicit types

Signed-off-by: John Howard <john.howard@solo.io>

---------

Signed-off-by: John Howard <john.howard@solo.io>

Author: howardjohn

CHANGELOG.md

@@ -4,6 +4,23 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.25.0]
+
+### Added
+
+- Added an off-by-default `protobuf-protox` feature to build protobuf support
+  without requiring an external `protoc` binary.
+
+### Changed
+
+- Updated `prost`, `prost-build`, and `prost-types` dependencies to `v0.14`.
+- The `prometheus_protobuf` feature generates and encodes Prometheus
+  `io.prometheus.client` protobuf messages from `metrics.proto` rather than the
+  OpenMetrics protobuf data model.
+  See [Issue](https://github.com/prometheus/OpenMetrics/issues/296) for more context.
+  The `protobuf` and `openmetrics_protobuf` features retain the old, deprecated, OpenMetrics protobuf support which will
+  be removed in a future release.
+
 ## [0.24.1]
 
 ### Added

CONTRIBUTING.md

@@ -6,6 +6,9 @@ The `build.rs` script in this library depends upon the
 [Protocol Buffers compiler][protoc]. Be sure that `protoc` is installed and
 available within your `PATH`.
 
+If you enable the off-by-default `protobuf-protox` feature, the build uses
+`protox` instead and does not require `protoc`.
+
 [protoc]: https://docs.rs/prost-build/latest/prost_build/#sourcing-protoc
 
 ## Python Dependencies

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "prometheus-client"
-version = "0.24.1"
+version = "0.25.0"
 authors = ["Max Inden <mail@max-inden.de>"]
 edition = "2021"
 description = "Open Metrics client library allowing users to natively instrument applications."
@@ -12,7 +12,10 @@ documentation = "https://docs.rs/prometheus-client"
 
 [features]
 default = []
-protobuf = ["dep:prost", "dep:prost-types", "dep:prost-build"]
+prometheus_protobuf = ["dep:prost", "dep:prost-types", "dep:prost-build"]
+openmetrics_protobuf = ["dep:prost", "dep:prost-types", "dep:prost-build"]
+protobuf = ["openmetrics_protobuf"]
+protobuf-protox = ["dep:protox"]
 
 # This feature provides additional APIs for testing downstream code using
 # `prometheus-client`.
@@ -29,8 +32,8 @@ dtoa = "1.0"
 itoa = "1.0"
 parking_lot = "0.12"
 prometheus-client-derive-encode = { version = "0.5.0", path = "derive-encode" }
-prost = { version = "0.12.0", optional = true }
-prost-types = { version = "0.12.0", optional = true }
+prost = { version = "0.14", optional = true }
+prost-types = { version = "0.14", optional = true }
 
 [dev-dependencies]
 async-std = { version = "1", features = ["attributes"] }
@@ -49,7 +52,8 @@ hyper-util = { version = "0.1.3", features = ["tokio"] }
 http-body-util = "0.1.1"
 
 [build-dependencies]
-prost-build = { version = "0.12.0", optional = true }
+prost-build = { version = "0.14", optional = true }
+protox = { version = "0.9.1", optional = true }
 
 [[bench]]
 name = "baseline"
@@ -73,7 +77,7 @@ required-features = []
 name = "proto"
 path = "benches/encoding/proto.rs"
 harness = false
-required-features = ["protobuf"]
+required-features = ["prometheus_protobuf"]
 
 # Passing arguments to the docsrs builder in order to properly document cfg's.
 # More information: https://docs.rs/about/builds#cross-compiling

benches/encoding/proto.rs

@@ -2,7 +2,7 @@
 // https://github.com/tikv/rust-prometheus/blob/ab1ca7285d3463504381a5025ae1951e020d6796/benches/text_encoder.rs:write
 
 use criterion::{black_box, criterion_group, criterion_main, Criterion};
-use prometheus_client::encoding::protobuf;
+use prometheus_client::encoding::prometheus_protobuf;
 use prometheus_client::metrics::counter::Counter;
 use prometheus_client::metrics::family::Family;
 use prometheus_client::metrics::histogram::{exponential_buckets, Histogram};
@@ -75,7 +75,7 @@ pub fn proto(c: &mut Criterion) {
         }
 
         b.iter(|| {
-            let metric_set = protobuf::encode(&registry).unwrap();
+            let metric_set = prometheus_protobuf::encode(&registry).unwrap();
             black_box(metric_set);
         })
     });

build.rs

@@ -1,11 +1,36 @@
-use std::io::Result;
-
-fn main() -> Result<()> {
-    #[cfg(feature = "protobuf")]
-    prost_build::compile_protos(
-        &["src/encoding/proto/openmetrics_data_model.proto"],
-        &["src/encoding/proto/"],
-    )?;
+use std::error::Error;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    #[cfg(any(feature = "prometheus_protobuf", feature = "openmetrics_protobuf"))]
+    compile_protos()?;
+
+    Ok(())
+}
+
+#[allow(clippy::vec_init_then_push)] // False positive due to feature flags
+#[cfg(any(feature = "prometheus_protobuf", feature = "openmetrics_protobuf"))]
+fn compile_protos() -> Result<(), Box<dyn Error>> {
+    let mut protos = Vec::new();
+
+    #[cfg(feature = "prometheus_protobuf")]
+    protos.push("src/encoding/proto/metrics.proto");
+    #[cfg(feature = "openmetrics_protobuf")]
+    protos.push("src/encoding/proto/openmetrics_data_model.proto");
+
+    let includes = ["src/encoding/proto/"];
+
+    #[cfg(feature = "protobuf-protox")]
+    prost_build::compile_fds(protox::compile(&protos, includes)?)?;
+
+    #[cfg(not(feature = "protobuf-protox"))]
+    prost_build::compile_protos(&protos, &includes)?;
+
+    for path in &protos {
+        println!("cargo:rerun-if-changed={}", path);
+    }
+    for path in &includes {
+        println!("cargo:rerun-if-changed={}", path);
+    }
 
     Ok(())
 }

derive-encode/Cargo.toml

@@ -17,7 +17,7 @@ quote = "1"
 syn = "2"
 
 [dev-dependencies]
-prometheus-client = { path = "../", features = ["protobuf"] }
+prometheus-client = { path = "../", features = ["prometheus_protobuf"] }
 trybuild = "1"
 
 [lib]

derive-encode/tests/lib.rs

@@ -47,8 +47,8 @@ fn basic_flow() {
 
 mod protobuf {
     use crate::{Labels, Method};
-    use prometheus_client::encoding::protobuf::encode;
-    use prometheus_client::encoding::protobuf::openmetrics_data_model;
+    use prometheus_client::encoding::prometheus_protobuf::encode;
+    use prometheus_client::encoding::prometheus_protobuf::prometheus_data_model;
     use prometheus_client::metrics::counter::Counter;
     use prometheus_client::metrics::family::Family;
     use prometheus_client::registry::Registry;
@@ -67,17 +67,15 @@ mod protobuf {
             })
             .inc();
 
-        // Encode all metrics in the registry in the OpenMetrics protobuf format.
-        let mut metric_set = encode(&registry).unwrap();
-        let mut family: openmetrics_data_model::MetricFamily =
-            metric_set.metric_families.pop().unwrap();
-        let metric: openmetrics_data_model::Metric = family.metrics.pop().unwrap();
+        let mut metric_families = encode(&registry).unwrap();
+        let mut family: prometheus_data_model::MetricFamily = metric_families.pop().unwrap();
+        let metric: prometheus_data_model::Metric = family.metric.pop().unwrap();
 
-        let method = &metric.labels[0];
+        let method = &metric.label[0];
         assert_eq!("method", method.name);
         assert_eq!("Get", method.value);
 
-        let path = &metric.labels[1];
+        let path = &metric.label[1];
         assert_eq!("path", path.name);
         assert_eq!("/metrics", path.value);
     }
@@ -96,13 +94,11 @@ mod protobuf {
             })
             .inc();
 
-        // Encode all metrics in the registry in the OpenMetrics protobuf format.
-        let mut metric_set = encode(&registry).unwrap();
-        let mut family: openmetrics_data_model::MetricFamily =
-            metric_set.metric_families.pop().unwrap();
-        let metric: openmetrics_data_model::Metric = family.metrics.pop().unwrap();
+        let mut metric_families = encode(&registry).unwrap();
+        let mut family: prometheus_data_model::MetricFamily = metric_families.pop().unwrap();
+        let metric: prometheus_data_model::Metric = family.metric.pop().unwrap();
 
-        let label = &metric.labels[0];
+        let label = &metric.label[0];
         assert_eq!("method", label.name);
         assert_eq!("Get", label.value);
     }