(fix): Prometheus path normalisation improvements

- Make case insensitive
- Ensure all regexes have anchors
- Omit query string with request.path

config/prometheus.js

@@ -19,23 +19,22 @@ const paths = [
   ],
   ["^/postcodes/[^/]+$", "/postcodes/:postcode"],
   ["^/postcodes/.+/validate$", "/postcodes/:postcode/validate"],
-  ["^/postcodes/.+/nearest", "/postcodes/:postcode/nearest"],
-  ["^/postcodes/.+/autocomplete", "/postcodes/:postcode/autocomplete"],
+  ["^/postcodes/.+/nearest$", "/postcodes/:postcode/nearest"],
+  ["^/postcodes/.+/autocomplete$", "/postcodes/:postcode/autocomplete"],
   ["^/outcodes/[^/]+$", "/outcodes/:outcode"],
   ["^/outcodes/.+/nearest$", "/outcodes/:outcode/nearest"],
   ["^/terminated_postcodes/[^/]+$", "/terminated_postcodes/:postcode"],
   ["^/places/[^/]+$", "/places/:code"],
-].map(([regex, path]) => [new RegExp(regex), path]);
+].map(([regex, path]) => [new RegExp(regex, "i"), path]);
 
 /**
  * Squash metrics with dynamic paths into one
  *
  * e.g. /postcodes/sw1a2aa -> /postcodes/:postcode
  */
 const normalizePath = request => {
-  const url = request.url;
   for (const [regex, path] of paths) {
-    if (regex.test(url)) return path;
+    if (regex.test(request.path)) return path;
   }
   return "other";
 };

tests/prometheus.integration.js

@@ -144,6 +144,12 @@ describe("Prometheus /metrics endpoint", () => {
         await testMetric(url, expectedMetric);
       });
 
+      it("normalises /PLACES/:code", async () => {
+        const url = "/PLACES/foobar";
+        const expectedMetric = "/places/:code";
+        await testMetric(url, expectedMetric);
+      });
+
       it("does not generate metrics for unexpected paths", async () => {
         const url = "/bogus";
         const expectedMetric = "other";