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fix: replace Mutex<DnsState> with OnceCell in NonLocalDnsResolver #2449

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Merged
svix-jplatte merged 4 commits into from
Jul 10, 2026
+14 −27
Merged

fix: replace Mutex<DnsState> with OnceCell in NonLocalDnsResolver #2449

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284b758
fix
Rohan-Singla Jul 10, 2026
0453fac
add test
Rohan-Singla Jul 10, 2026
cf3bbd7
remove test and fix
Rohan-Singla Jul 10, 2026
41fe192
run fmt
Rohan-Singla Jul 10, 2026
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41 changes: 14 additions & 27 deletions server/svix-server/src/core/webhook_http_client.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -36,7 +36,7 @@ use ipnet::IpNet;
use openssl::ssl::{SslConnector, SslConnectorBuilder, SslMethod, SslVerifyMode};
use serde::Serialize;
use thiserror::Error;
use tokio::{net::TcpStream, sync::Mutex};
use tokio::{net::TcpStream, sync::OnceCell};
use tower::Service;

use crate::{
Expand Down Expand Up @@ -561,21 +561,15 @@ type NonLocalHttpConnector = HttpConnector<NonLocalDnsResolver>;
/// Specific private subnets or domain names may be whitelisted.
#[derive(Clone, Debug)]
struct NonLocalDnsResolver {
state: Arc<Mutex<DnsState>>,
resolver: Arc<OnceCell<TokioResolver>>,
whitelist_nets: Arc<Vec<IpNet>>,
whitelist_names: Arc<Vec<String>>,
}

#[derive(Clone, Debug)]
enum DnsState {
Init,
Ready(Arc<TokioResolver>),
}

impl NonLocalDnsResolver {
pub fn new(whitelist_nets: Arc<Vec<IpNet>>, whitelist_names: Arc<Vec<String>>) -> Self {
NonLocalDnsResolver {
state: Arc::new(Mutex::new(DnsState::Init)),
resolver: Arc::new(OnceCell::new()),
whitelist_nets,
whitelist_names,
}
Expand All @@ -592,24 +586,12 @@ impl Service<Name> for NonLocalDnsResolver {
}

fn call(&mut self, name: Name) -> Self::Future {
let resolver = self.clone();
let this = self.clone();
let whitelist_nets = self.whitelist_nets.clone();
let whitelist_names = self.whitelist_names.clone();

Box::pin(async move {
let mut lock = resolver.state.lock().await;

let resolver = match &*lock {
DnsState::Init => {
let resolver = new_resolver().await?;
*lock = DnsState::Ready(resolver.clone());
resolver
}

DnsState::Ready(resolver) => resolver.clone(),
};

drop(lock);
let resolver = this.resolver.get_or_try_init(new_resolver).await?;

let whitelisted_name = whitelist_names
.iter()
Expand Down Expand Up @@ -653,10 +635,15 @@ impl Iterator for SocketAddrs {
}
}

async fn new_resolver() -> Result<Arc<TokioResolver>, NetError> {
let mut builder = Resolver::builder_tokio()?;
builder.options_mut().ip_strategy = hickory_resolver::config::LookupIpStrategy::Ipv4thenIpv6;
Ok(Arc::new(builder.build()?))
async fn new_resolver() -> Result<TokioResolver, NetError> {
tokio::task::spawn_blocking(|| {
let mut builder = Resolver::builder_tokio()?;
builder.options_mut().ip_strategy =
hickory_resolver::config::LookupIpStrategy::Ipv4thenIpv6;
builder.build()
})
.await
.unwrap_or_else(|e| std::panic::resume_unwind(e.into_panic()))

@svix-jplatte svix-jplatte Jul 10, 2026 •
edited
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Nice! I hadn't encountered this pattern before, but it seems more sensible than a plain unwrap.

@Rohan-Singla Rohan-Singla Jul 11, 2026

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Ahan cool!

}

fn is_allowed(addr: IpAddr) -> bool {
Expand Down
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