Allow Stale phase in cache_miss

There could be a race condition where a Stale request waiting on cache
lock retries the cache lock and lookup, but enters cache_miss after
finding the asset is no longer present.

1 files changed, 2 insertions, 1 deletions

diff --git a/pingora-cache/src/lib.rs b/pingora-cache/src/lib.rs
index 86cfbdf..a999f7e 100644
--- a/pingora-cache/src/lib.rs
+++ b/pingora-cache/src/lib.rs
@@ -493,7 +493,8 @@ impl HttpCache {
         match self.phase {
             // from CacheKey: set state to miss during cache lookup
             // from Bypass: response became cacheable, set state to miss to cache
-            CachePhase::CacheKey | CachePhase::Bypass => {
+            // from Stale: waited for cache lock, then retried and found asset was gone
+            CachePhase::CacheKey | CachePhase::Bypass | CachePhase::Stale => {
                 self.phase = CachePhase::Miss;
                 self.inner_mut().traces.start_miss_span();
             }