diff --git a/src/helpers/metrics.ts b/src/helpers/metrics.ts
index 230ed981..2ab48449 100644
--- a/src/helpers/metrics.ts
+++ b/src/helpers/metrics.ts
@@ -109,3 +109,8 @@ new client.Gauge({
     });
   }
 });
+
+export const requestDeduplicatorSize = new client.Gauge({
+  name: 'request_deduplicator_size',
+  help: 'Total number of items in the deduplicator queue'
+});
diff --git a/src/helpers/requestDeduplicator.ts b/src/helpers/requestDeduplicator.ts
index 55e21964..3fc33d93 100644
--- a/src/helpers/requestDeduplicator.ts
+++ b/src/helpers/requestDeduplicator.ts
@@ -1,3 +1,4 @@
+import { requestDeduplicatorSize } from './metrics';
 import { sha256 } from './utils';
 
 const ongoingRequests = new Map();
@@ -7,15 +8,16 @@ export default async function serve(id, action, args) {
   if (!ongoingRequests.has(key)) {
     const requestPromise = action(...args)
       .then(result => {
-        ongoingRequests.delete(key);
         return result;
       })
       .catch(e => {
-        ongoingRequests.delete(key);
         throw e;
+      }).finally(() => {
+        ongoingRequests.delete(key);
       });
     ongoingRequests.set(key, requestPromise);
   }
 
+  requestDeduplicatorSize.set(ongoingRequests.size);
   return ongoingRequests.get(key);
 }