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Make tls optional and add rustls support (#418) #420

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Make tls optional and add rustls support (#418) #420

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5 changes: 4 additions & 1 deletion metrics-exporter-prometheus/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,9 @@ keywords = ["metrics", "telemetry", "prometheus"]
default = ["http-listener", "push-gateway"]
async-runtime = ["tokio", "hyper"]
http-listener = ["async-runtime", "hyper/server", "ipnet"]
push-gateway = ["async-runtime", "hyper/client", "hyper-tls", "tracing"]
push-gateway = ["async-runtime", "hyper/client", "tracing"]
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When it comes to the core crates (like metrics), I generally err on the side of making users opt-in to additional functionality, but that flips the opposite direction for exporters, where users generally want/expect to get the "full fat" support out of the box.

I'd say we should add another feature called push-gateway-https, which pulls in hyper-rustls, and have the feature be enabled by default.

native-tls = ["hyper-tls"]
rustls-tls = ["hyper-rustls"]
Comment on lines +24 to +25
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After doing some reading, it seems like we should probably just switch to using rustls entirely.

I don't think the initial implementor choose to use hyper-tls specifically for the OS-backed/dynamically-linked aspect, and I don't personally care about esoteric SSL/TLS setups or FIPS compliance or any of that... so I'd rather go with a single solution than force users to have to spend time understanding which one they ought to choose.

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I hope you won't mind a somewhat random drive-past, but its generally a good practice for mid-layer crates that sit between TLS and applications to not set TLS policy.

The way to make this work comfortably is:

  • at a dependency level consume hyper, or whatever other crates you use, with default-features-false
  • have a feature to turn on the push-gateway without specifying the TLS stack to use
  • have a different feature to turn on the push-gateway with whatever tls stack you prefer to have by default

Then higher layer crates such as axum-prometheus can depend on your crate, with default-features=false, and the application layer crate using axum-prometheus can specify hyper-tls or hyper-rustls itself.


[dependencies]
metrics = { version = "^0.21", path = "../metrics" }
Expand All @@ -36,6 +38,7 @@ ipnet = { version = "2", optional = true }
tokio = { version = "1", features = ["rt", "net", "time"], optional = true }
tracing = { version = "0.1.26", optional = true }
hyper-tls = { version = "0.5.0", optional = true }
hyper-rustls = { version = "0.24.2", optional = true }

[dev-dependencies]
tracing = "0.1"
Expand Down
26 changes: 23 additions & 3 deletions metrics-exporter-prometheus/src/builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,6 @@ use hyper::{
http::HeaderValue,
Method, Request, Uri,
};
use hyper_tls::HttpsConnector;

use indexmap::IndexMap;
#[cfg(feature = "http-listener")]
Expand Down Expand Up @@ -461,8 +460,8 @@ impl PrometheusBuilder {
#[cfg(feature = "push-gateway")]
ExporterConfig::PushGateway { endpoint, interval, username, password } => {
let exporter = async move {
let https = HttpsConnector::new();
let client = Client::builder().build::<_, hyper::Body>(https);
let client = make_http_client();

let auth = username.as_ref().map(|name| basic_auth(name, password.as_deref()));

loop {
Expand Down Expand Up @@ -568,6 +567,27 @@ fn basic_auth(username: &str, password: Option<&str>) -> HeaderValue {
header
}

#[cfg(all(feature = "rustls-tls", not(feature = "native-tls")))]
fn make_http_client(
) -> Client<hyper_rustls::HttpsConnector<hyper::client::HttpConnector>, hyper::Body> {
let tls = hyper_rustls::HttpsConnectorBuilder::new()
.with_native_roots()
.https_or_http()
.enable_http1()
.build();
Client::builder().build::<_, hyper::Body>(tls)
}

#[cfg(all(not(feature = "rustls-tls"), feature = "native-tls"))]
fn make_http_client() -> Client<hyper_tls::HttpsConnector, hyper::Body> {
Client::builder().build::<_, hyper::Body>(hyper_tls::HttpsConnector::new())
}

#[cfg(not(any(feature = "rustls-tls", feature = "native-tls")))]
fn make_http_client() -> Client<hyper::client::HttpConnector, hyper::Body> {
Client::builder().build_http()
}

#[cfg(test)]
mod tests {
use std::time::Duration;
Expand Down