Cleanup Schema cache per request (#6126)

* remove enableSingleSchemaCache from test

* clear schema cache per request

src/PromiseRouter.js

@@ -153,6 +153,7 @@ function makeExpressHandler(appId, promiseHandler) {
       promiseHandler(req)
         .then(
           result => {
+            clearSchemaCache(req);
             if (!result.response && !result.location && !result.text) {
               log.error(
                 'the handler did not include a "response" or a "location" field'
@@ -186,13 +187,18 @@ function makeExpressHandler(appId, promiseHandler) {
             }
             res.json(result.response);
           },
-          error => next(error)
+          error => {
+            clearSchemaCache(req);
+            next(error);
+          }
         )
         .catch(e => {
+          clearSchemaCache(req);
           log.error(`Error generating response. ${inspect(e)}`, { error: e });
           next(e);
         });
     } catch (e) {
+      clearSchemaCache(req);
       log.error(`Error handling request: ${inspect(e)}`, { error: e });
       next(e);
     }
@@ -210,3 +216,9 @@ function maskSensitiveUrl(req) {
   }
   return maskUrl;
 }
+
+function clearSchemaCache(req) {
+  if (req.config && !req.config.enableSingleSchemaCache) {
+    req.config.database.schemaCache.clear();
+  }
+}