Set up URL rewrite for a classic Application Load Balancer

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:

Before you begin

Read about URL rewrites .
Read about URL maps in general and path matchers 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 .

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

  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

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

Go to the Load balancing page in the Google Cloud console.
Go to the Load balancing page
Click http-lb .
Click Edit .
Keep the window open to continue.

Change the host and path rules

In the left column of the screen, click Host and path rules.
Select Advanced host and path rule (URL redirect, URL rewrite).
Click the row that contains the non-default path rule, in this case, the row that has an asterisk ( * ) for all hosts.
Click the pencil icon for the /love-to-fetch/* Route traffic to a single backend: dogs row.
Under Paths, delete /love-to-fetch/* and add /* .
Under Action, select Route traffic to a single backend.
Click Add-on action (URL rewrite).
Leave Host rewriteblank.
Under Path prefix rewrite, enter /love-to-fetch/ .
Under Backend, select dogs .
Click Save.
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
If everything looks correct, click Updateto update your HTTP load balancer.

Paths	Action	Backend
Any unmatched (default)	Route traffic to a single backend	cats
/*	Route traffic to a single backend	dogs

gcloud

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/* .

  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

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.

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 .