This example demonstrates rewriting the path specified in a request for a classic Application Load Balancer. To configure traffic management for global external Application Load Balancers and regional external Application Load Balancers, see the following pages: - [Setting up traffic management for global external Application Load Balancer](https://docs.cloud.google.com/load-balancing/docs/https/setting-up-global-traffic-mgmt#rewrite-url) - [Setting up traffic management for regional external Application Load Balancer](https://docs.cloud.google.com/load-balancing/docs/https/setting-up-reg-traffic-mgmt#rewrite-url) ### Before you begin - Read about [URL rewrites](https://docs.cloud.google.com/load-balancing/docs/https/traffic-management.md.txt#rewrites). - Read about [URL maps in general](https://docs.cloud.google.com/load-balancing/docs/url-map-concepts.md.txt) and [path matchers](https://docs.cloud.google.com/load-balancing/docs/url-map-concepts.md.txt#pm-constraints) in particular. - The URL rewrite example assumes that you've already created your external Application Load Balancer following the steps outlined in [Setting up a load balancer with Cloud Storage buckets](https://docs.cloud.google.com/load-balancing/docs/https/ext-load-balancer-backend-buckets). That example leads you through the creation of two resources: - `http://IP_ADDRESS/never-fetch/three-cats.jpg` - `http://IP_ADDRESS/love-to-fetch/two-dogs.jpg` Where `/never-fetch/three-cats.jpg` is stored in `/cats`, which is the default service, and `/love-to-fetch/two-dogs.jpg` is stored in `/dogs`. At this point, the URL map looks like this: ``` gcloud compute url-maps describe http-lb ``` ```yaml creationTimestamp: '2020-10-13T11:18:10.561-07:00' defaultService: https://www.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets/cats fingerprint: MKfYsObzqgw= hostRules: - hosts: - '*' pathMatcher: path-matcher-1 id: '1420501688756228493' kind: compute#urlMap name: test-bucket pathMatchers: - defaultService: https://www.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets/cats name: path-matcher-1 pathRules: - paths: - /love-to-fetch/* service: https://www.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets/dogs selfLink: https://www.googleapis.com/compute/v1/projects/PROJECT_ID/global/urlMaps/http-lb ``` ### Modifying the URL map > [!IMPORTANT] > **Important:** The rewrite is prepended to the path as is. Full path rewrites are not supported. External Application Load Balancers only implement path prefix rewrites. For example, you *can* rewrite: `host.name/path1/resource1` to `host.name/path2/resource1`. You *cannot* rewrite `host.name/path1/resource1` to `host.name/path1/resource2`. In this example, you rewrite the `/love-to-fetch/` URL so that users can reach the `two-dogs.jpg` image with this simplified URL: - `http://IP_ADDRESS/two-dogs.jpg` To do this, modify the load balancer's URL map as follows: ### Console ### Edit your load balancer 1. Go to the Load balancing page in the Google Cloud console. [Go to the Load balancing page](https://console.cloud.google.com/networking/loadbalancing/add) 2. Click `http-lb`. 3. Click **Edit** . 4. Keep the window open to continue. ### Change the host and path rules 1. In the left column of the screen, click **Host and path rules**. 2. Select **Advanced host and path rule (URL redirect, URL rewrite)**. 3. Click the row that contains the non-default path rule, in this case, the row that has an asterisk (`*`) for all hosts. 4. Click the pencil icon for the `/love-to-fetch/* Route traffic to a single backend: dogs` row. 5. Under **Paths** , delete `/love-to-fetch/*` and add `/*`. 6. Under **Action** , select **Route traffic to a single backend**. 7. Click **Add-on action (URL rewrite)**. 8. Leave **Host rewrite** blank. 9. Under **Path prefix rewrite** , enter `/love-to-fetch/`. 10. Under **Backend** , select `dogs`. 11. Click **Save**. 12. Click **Done**. The new host and path rule looks as follows: | Paths | Action | Backend | |---|---|---| | Any unmatched (default) | Route traffic to a single backend | cats | | /\* | Route traffic to a single backend | dogs |
13. If everything looks correct, click **Update** to update your HTTP load balancer. ### gcloud 1. Create a YAML file `/tmp/http-lb.yaml`, making sure to substitute PROJECT_ID with your project ID. When a user requests path `/*`, the path gets rewritten in the backend to the actual location of the content, which is `/love-to-fetch/*`. ```yaml defaultService: https://www.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets/cats hostRules: - hosts: - '*' pathMatcher: path-matcher-1 name: http-lb pathMatchers: - defaultService: https://www.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets/cats name: path-matcher-1 pathRules: - paths: - /* routeAction: urlRewrite: pathPrefixRewrite: /love-to-fetch/ service: https://www.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets/dogs tests: - description: Test routing to backend bucket, dogs host: example.com path: /love-to-fetch/test service: https://www.googleapis.com/compute/v1/projects/PROJECT_ID/global/backendBuckets/dogs ``` 2. Validate the URL map. ``` gcloud compute url-maps validate --source /tmp/http-lb.yaml ``` If the tests pass and the command outputs a success message, save the changes to the URL map. 3. Update the URL map. ``` gcloud compute url-maps import http-lb \ --source /tmp/http-lb.yaml \ --global ``` ### Testing Note the IPv4 address that was reserved: ``` gcloud compute addresses describe example-ip \ --format="get(address)" \ --global ``` After waiting several minutes for the changes to propagate, you can test this setup. On the command line, run the following curl command: ``` curl http://IP_ADDRESS/two-dogs.jpg ``` In a browser, open `http://IP_ADDRESS/two-dogs.jpg`. ## What's next - [Clean up the load balancer setup](https://docs.cloud.google.com/load-balancing/docs/cleaning-up-lb-setup.md.txt).