[Access Tokens] Add cache for valid access tokens (#27709)

Add 60 second cache for valid tokens, so we don't have to re-validate an access token on every request.

GitOrigin-RevId: ac6ca92fc453679839f4019fa9dbf7ad28425352

Author: jordanhunt22

crates/common/src/http/fetch.rs

@@ -1,6 +1,12 @@
-use std::collections::{
-    BTreeMap,
-    HashMap,
+use std::{
+    collections::{
+        BTreeMap,
+        HashMap,
+    },
+    sync::atomic::{
+        AtomicU64,
+        Ordering,
+    },
 };
 
 use async_trait::async_trait;
@@ -135,12 +141,14 @@ type HandlerFn = Box<
 
 pub struct StaticFetchClient {
     router: BTreeMap<url::Url, HashMap<http::Method, HandlerFn>>,
+    num_calls: AtomicU64,
 }
 
 impl StaticFetchClient {
     pub fn new() -> Self {
         Self {
             router: BTreeMap::new(),
+            num_calls: AtomicU64::new(0),
         }
     }
 
@@ -156,11 +164,17 @@ impl StaticFetchClient {
             .or_default()
             .insert(method, Box::new(handler));
     }
+
+    /// Returns how many times a fetch client has been called
+    pub fn num_calls(&self) -> u64 {
+        self.num_calls.load(Ordering::Relaxed)
+    }
 }
 
 #[async_trait]
 impl FetchClient for StaticFetchClient {
     async fn fetch(&self, request: HttpRequestStream) -> anyhow::Result<HttpResponseStream> {
+        self.num_calls.fetch_add(1, Ordering::Relaxed);
         let handler = self
             .router
             .get(&request.url)

crates/common/src/knobs.rs

@@ -1058,3 +1058,10 @@ pub static REQUEST_TRACE_SAMPLE_CONFIG: LazyLock<SamplingConfig> =
 /// the "backend_startup" domain keyed by db cluster name.
 pub static STARTUP_RATE_LIMIT_ENABLED: LazyLock<bool> =
     LazyLock::new(|| env_config("STARTUP_RATE_LIMIT_ENABLED", false));
+
+/// Size of the cache for access token authentication
+pub static AUTH_CACHE_SIZE: LazyLock<usize> = LazyLock::new(|| env_config("AUTH_CACHE_SIZE", 1000));
+
+/// Length of time an entry to the access authentication cache is valid
+pub static AUTH_CACHE_TTL_SECONDS: LazyLock<u64> =
+    LazyLock::new(|| env_config("AUTH_CACHE_TTL_SECONDS", 60));