Switch from protobuf to prost

Cargo.toml

@@ -19,9 +19,9 @@ features = ["nightly"]
 
 [features]
 default = ["protobuf"]
-gen = ["protobuf-codegen-pure"]
 nightly = ["libc"]
 process = ["libc", "procfs"]
+protobuf = ["prost", "prost-build"]
 push = ["reqwest", "libc", "protobuf"]
 
 [dependencies]
@@ -30,7 +30,7 @@ fnv = "^1.0"
 lazy_static = "^1.4"
 libc = { version = "^0.2", optional = true }
 parking_lot = "^0.11"
-protobuf = { version = "^2.0", optional = true }
+prost = { version = "^0.7", optional = true }
 memchr = "^2.3"
 reqwest = { version = "^0.11", features = ["blocking"], optional = true }
 thiserror = "^1.0"
@@ -45,7 +45,7 @@ hyper = { version = "^0.14", features = ["server", "http1", "tcp"] }
 tokio = { version = "^1.0", features = ["macros", "rt-multi-thread"] }
 
 [build-dependencies]
-protobuf-codegen-pure = { version = "^2.0", optional = true }
+prost-build = { version = "^0.7", optional = true }
 
 [workspace]
 members = ["static-metric"]

README.md

@@ -18,8 +18,9 @@ Find the latest documentation at <https://docs.rs/prometheus>.
 
 This crate provides several optional components which can be enabled via [Cargo `[features]`](https://doc.rust-lang.org/cargo/reference/features.html):
 
-- `gen`: To generate protobuf client with the latest protobuf version instead of
-  using the pre-generated client.
+- `protobuf`: Enable [Protocol Buffers](https://developers.google.com/protocol-buffers/) (aka Protobuf)  based exposition format. (Enabled by default)
+
+> Notice: Since version 2.0, Prometheus no longer supports the Protobuf-based format. You can read about the reasoning behind this change in [this document](https://github.com/OpenObservability/OpenMetrics/blob/master/legacy/markdown/protobuf_vs_text.md).
 
 - `nightly`: Enable nightly only features.
 

build.rs

@@ -1,17 +1,11 @@
 // Copyright 2019 TiKV Project Authors. Licensed under Apache-2.0.
 
-#[cfg(feature = "gen")]
+#[cfg(feature = "protobuf")]
 fn generate_protobuf_binding_file() {
-    protobuf_codegen_pure::run(protobuf_codegen_pure::Args {
-        out_dir: "proto",
-        input: &["proto/proto_model.proto"],
-        includes: &["proto"],
-        ..Default::default()
-    })
-    .unwrap();
+    prost_build::compile_protos(&["proto/proto_model.proto"], &["proto"]).unwrap();
 }
 
-#[cfg(not(feature = "gen"))]
+#[cfg(not(feature = "protobuf"))]
 fn generate_protobuf_binding_file() {}
 
 fn main() {