Sort the paths in routes to ensure matcher picks nearest regex to req…

…uest uri (#687)

* Test only

Signed-off-by: PKhivasra <[email protected]>

* Sort the paths in routes to ensure matcher picks nearest regex to request uri

When the default backend routes are registered, currently it is as per unordered map. This means that the routes can have "" or "\api\v1" before "api\v1\query_range". When the router matches the regex expression (Refs: https://gecgithub01.walmart.com/Telemetry/trickster-v2/blob/main/pkg/router/route.go#L40 https://gecgithub01.walmart.com/Telemetry/trickster-v2/blob/main/pkg/router/regexp.go#L323) with the routes map, if partial routes appears first that will be considered as a match, which causes request to be "Proxy-Only".
Thus, with sorting we will ensure that routes will be a sorted array in the descending order of path lengths, meaning: "\api\v1\query_range" would appear before "api\v1" and "" so that we have appropriate match.
Issue:#594

Signed-off-by: PKhivasra <[email protected]>

---------

Signed-off-by: PKhivasra <[email protected]>

pkg/routing/routing.go

@@ -383,7 +383,20 @@ func RegisterDefaultBackendRoutes(router router.Router, bknds backends.Backends,
 			}
 			tl.Info(logger,
 				"registering default backend handler paths", tl.Pairs{"backendName": o.Name})
-			for _, p := range o.Paths {
+
+			// Sort by key length(Path length) to ensure /api/v1/query_range appear before /api/v1 or / path in regex path matching
+			keylist := make([]string, 0, len(o.Paths))
+			for key := range o.Paths {
+				keylist = append(keylist, key)
+			}
+			sort.Sort(ByLen(keylist))
+			for i := len(keylist)/2 - 1; i >= 0; i-- {
+				opp := len(keylist) - 1 - i
+				keylist[i], keylist[opp] = keylist[opp], keylist[i]
+			}
+
+			for _, k := range keylist {
+				var p = o.Paths[k]
 				if p.Handler != nil && len(p.Methods) > 0 {
 					tl.Debug(logger, "registering default backend handler paths",
 						tl.Pairs{"backendName": o.Name, "path": p.Path, "handlerName": p.HandlerName,