feat(config): Opt-out of DNS cache

CHANGELOG.md

@@ -16,6 +16,7 @@
 - Populate gen_ai.response.model from gen_ai.request.model if not already set. ([#5654](https://github.com/getsentry/relay/pull/5654))
 - Add support for Unix domain sockets for statsd metrics. ([#5668](https://github.com/getsentry/relay/pull/5668))
 - Support `deployment.environment` OTLP resource attribute for setting the Sentry environment. ([#5691](https://github.com/getsentry/relay/pull/5691))
+- Allow users to opt-out of DNS caching. ([#5700](https://github.com/getsentry/relay/pull/5700))
 
 **Internal**:
 

relay-config/src/config.rs

@@ -883,6 +883,10 @@ pub struct Http {
     ///
     /// The forward endpoint forwards unknown API requests to the upstream.
     pub forward: bool,
+    /// Enables an async DNS resolver through the `hickory-dns` crate, which uses an LRU cache for
+    /// the resolved entries. This helps to limit the amount of requests made to the upstream DNS
+    /// server (important for K8s infrastructure).
+    pub dns_cache: bool,
 }
 
 impl Default for Http {
@@ -899,6 +903,7 @@ impl Default for Http {
             encoding: HttpEncoding::Zstd,
             global_metrics: false,
             forward: true,
+            dns_cache: true,
         }
     }
 }
@@ -2226,6 +2231,11 @@ impl Config {
         Duration::from_secs(self.values.http.max_retry_interval.into())
     }
 
+    /// Returns `true` if relay should use an in-process cache for DNS lookups.
+    pub fn http_dns_cache(&self) -> bool {
+        self.values.http.dns_cache
+    }
+
     /// Returns the expiry timeout for cached projects.
     pub fn project_cache_expiry(&self) -> Duration {
         Duration::from_secs(self.values.cache.project_expiry.into())

relay-server/src/services/upstream.rs

@@ -862,10 +862,7 @@ impl SharedClient {
             // In the forward endpoint, this means that content negotiation is done twice, and the
             // response body is first decompressed by the client, then re-compressed by the server.
             .gzip(true)
-            // Enables async resolver through the `hickory-dns` crate, which uses an LRU cache for
-            // the resolved entries. This helps to limit the amount of requests made to upstream DNS
-            // server (important for K8s infrastructure).
-            .hickory_dns(true)
+            .hickory_dns(config.http_dns_cache())
             .build()
             .unwrap();