Set up header and query parameter-based routing for the classic Application Load Balancer

This page includes two examples for classic Application Load Balancer:

Set up query parameter-based routing
Set up HTTP header-based routing

To configure traffic management for the global external Application Load Balancer and the regional external Application Load Balancer, see the following pages:

Before you begin

Read the Traffic management overview for external Application Load Balancers .
Be familiar with the URL map API .

Set up query parameter-based routing

This example demonstrates using query parameters to do A/B testing by matching on the query string.

Add two backend instance groups

For routing to be useful, you must have multiple backends.

To set up two backends, your VMs need to be in two instance groups. This guide describes how to create managed instance groups with Linux VMs that have Apache running and then set up load balancing.

The managed instance groups provide VMs running the backend servers of an external HTTP load balancer. For demonstration purposes, backends serve their own hostnames.

For simplicity, the backends reside in the same region. If you want a multi-region setup, you must have an instance template setup for the second region.

Console

Create an instance template. In the Google Cloud console, go to the Instance templatespage.

Go to Instance templates
1. Click Create instance template.
2. For Name, enter lb-backend-template .
3. Ensure that the Boot diskis set to a Debian image, such as Debian GNU/Linux 12 (bookworm). These instructions use commands that are only available on Debian, such as apt-get .
4. Click Advanced options.
5. Click Networkingand configure the following field:
  1. For Network tags, enter allow-health-check .
6. Click Management. Enter the following script into the Startup scriptfield.
```
#! /bin/bash
apt-get update
apt-get install apache2 -y
a2ensite default-ssl
a2enmod ssl
vm_hostname="$(curl -H "Metadata-Flavor:Google" \
http://metadata.google.internal/computeMetadata/v1/instance/name)"
echo "Page served from: $vm_hostname" | \
tee /var/www/html/index.html
systemctl restart apache2
```
7. Click Create.
Create a managed instance group. Go to the Instance groupspage in the Google Cloud console.

Go to Instance groups
1. Click Create instance group.
2. Select New managed instance group (stateless). For more information, see Stateless or stateful MIGs .
3. For Name, enter first-example-ig .
4. Under Location, select Single zone.
5. For Region, select your preferred region. This example uses us-east1 .
6. For Zone, select us-east1-b .
7. Under Instance template, select the instance template lb-backend-template .
8. Under Maximum number of instances, enter 2 .
9. Under Autoscaling mode, select Off:do not autoscale .
10. Click Create.

Create another managed instance group like this one. Name the second one second-example-ig , and base it on the lb-backend-template template.

gcloud

Create an instance template.

gcloud compute instance-templates create lb-backend-template \
   --region=us-east1 \
   --network=default \
   --subnet=default \
   --tags=allow-health-check \
   --image-family=debian-12 \
   --image-project=debian-cloud \
   --metadata=startup-script='#! /bin/bash
     apt-get update
     apt-get install apache2 -y
     a2ensite default-ssl
     a2enmod ssl
     vm_hostname="$(curl -H "Metadata-Flavor:Google" \
     http://metadata.google.internal/computeMetadata/v1/instance/name)"
     echo "Page served from: $vm_hostname" | \
     tee /var/www/html/index.html
     systemctl restart apache2'

Create the first managed instance group based on the template.

gcloud compute instance-groups managed create first-example-ig \
   --template=lb-backend-template --size=2 --zone=us-east1-b

Create the second managed instance group based on the template.

gcloud compute instance-groups managed create second-example-ig \
   --template=lb-backend-template --size=2 --zone=us-east1-c

Configuring a firewall rule

In this example, you create the fw-allow-health-check firewall rule. This is an ingress rule that allows traffic from the Google Cloud health checking systems ( 130.211.0.0/22 and 35.191.0.0/16 ). This example uses the target tag allow-health-check to identify the VMs.

Console

In the Google Cloud console, go to the Firewall policiespage.
Go to Firewall policies
Click Create firewall ruleto create the second firewall rule:
Enter a Nameof fw-allow-health-check .
Under Network, select Default .
Under Targets, select Specified target tags.
Populate the Target tagsfield with allow-health-check .
Set Source filterto IPv4 ranges.
Set Source IPv4 rangesto 130.211.0.0/22 and 35.191.0.0/16 .
Under Protocols and ports, select Specified protocols and ports.
Select the TCPcheckbox and enter 80 for the port numbers.
Click Create.

gcloud

gcloud compute firewall-rules create fw-allow-health-check \
    --network=default \
    --action=allow \
    --direction=ingress \
    --source-ranges=130.211.0.0/22,35.191.0.0/16 \
    --target-tags=allow-health-check \
    --rules=tcp

Reserving an external IP address

Now that your instances are up and running, set up a global static external IP address that your customers use to reach your load balancer.

Console

Go to the External IP addresses page in the Google Cloud console.
Go to the External IP addresses page
Click Reserve static addressto reserve an IPv4 address.
Assign a Nameof lb-ipv4-1 .
Set the Network tier to Standard.
Set the IP versionto IPv4.
Set the Typeto Global.
Click Reserve.
Ensure that the Typeis set to Global.
Click Reserve.

gcloud

gcloud compute addresses create lb-ipv4-1 \
    --ip-version=IPV4 \
    --network-tier=PREMIUM \
    --global

Note the IPv4 address that was reserved:

gcloud compute addresses describe lb-ipv4-1 \
    --format="get(address)" \
    --global

Setting up the load balancer backends

Console

The Google Cloud console is currently unsupported for setting up header-based and parameter-based routing. Use gcloud or the API instead.

gcloud

Create a health check .

gcloud compute health-checks create http http-basic-check \
        --port 80

Create the first backend service .
- For a global external Application Load Balancer, use the gcloud CLI command with load-balancing-scheme=EXTERNAL_MANAGED . This setting offers advanced traffic management capability .
- For an classic Application Load Balancer, use load-balancing-scheme=EXTERNAL .
```
gcloud compute backend-services create service-a \
        --load-balancing-scheme= LOAD_BALANCING_SCHEME 
\
        --global-health-checks \
        --protocol HTTP \
        --health-checks http-basic-check \
        --global
```

Create the second backend service .

gcloud compute backend-services create service-b \
        --load-balancing-scheme= LOAD_BALANCING_SCHEME 
\
        --global-health-checks \
        --protocol HTTP \
        --health-checks http-basic-check \
        --global

Add your first instance group as the backend to the first backend service.

gcloud compute backend-services add-backend service-a \
        --balancing-mode=UTILIZATION \
        --max-utilization=0.8 \
        --capacity-scaler=1 \
        --instance-group=first-example-ig \
        --instance-group-zone=us-east1-b \
        --global

Add your second instance group as the backend to the second backend service.

gcloud compute backend-services add-backend service-b \
        --balancing-mode=UTILIZATION \
        --max-utilization=0.8 \
        --capacity-scaler=1 \
        --instance-group=second-example-ig \
        --instance-group-zone=us-east1-c \
        --global

Creating the URL map

Console

The Google Cloud console is currently unsupported for setting up header-based and parameter-based routing. Use gcloud or the API instead.

gcloud

Create a YAML file /tmp/web-map-http.yaml . Replace PROJECT_ID with your project ID.

  defaultService 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-a 
 hostRules 
 : 
 - 
  
 hosts 
 : 
  
 - 
  
 '*' 
  
 pathMatcher 
 : 
  
 path-matcher-1 
 name 
 : 
  
 web-map-http 
 pathMatchers 
 : 
 - 
  
 defaultService 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-a 
  
 name 
 : 
  
 path-matcher-1 
  
 routeRules 
 : 
  
 - 
  
 matchRules 
 : 
  
 - 
  
 prefixMatch 
 : 
  
 / 
  
 queryParameterMatches 
 : 
  
 - 
  
 name 
 : 
  
 ABTest 
  
 exactMatch 
 : 
  
 A 
  
 priority 
 : 
  
 0 
  
 service 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-a 
  
 - 
  
 matchRules 
 : 
  
 - 
  
 prefixMatch 
 : 
  
 / 
  
 queryParameterMatches 
 : 
  
 - 
  
 name 
 : 
  
 ABTest 
  
 exactMatch 
 : 
  
 B 
  
 priority 
 : 
  
 1 
  
 service 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-b 
 selfLink 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/urlMaps/web-map-http 
 tests 
 : 
 - 
  
 description 
 : 
  
 Test routing for query ABTest with A 
  
 host 
 : 
  
 example.com 
  
 path 
 : 
  
 /?ABTest=A 
  
 service 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-a 
  
 expectedOutputUrl 
 : 
  
 http://example.com/?ABTest=A 
 - 
  
 description 
 : 
  
 Test routing for query ABTest with B 
  
 host 
 : 
  
 example.com 
  
 path 
 : 
  
 /?ABTest=B 
  
 service 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-b 
  
 expectedOutputUrl 
 : 
  
 http://example.com/?ABTest=B

Validate the URL map.
```
gcloud compute url-maps validate --source /tmp/web-map-http.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 web-map-http \
   --source /tmp/web-map-http.yaml \
   --global

Creating the target proxy and forwarding rule

Console

The Google Cloud console is currently unsupported for setting up header-based and parameter-based routing. Use gcloud or the API instead.

gcloud

Create a target HTTP proxy to route requests to your URL map.

gcloud compute target-http-proxies create http-lb-proxy \
        --url-map web-map-http

Create a global forwarding rule to route incoming requests to the proxy.
- For a global external Application Load Balancer, use the gcloud CLI command with load-balancing-scheme=EXTERNAL_MANAGED . This setting offers advanced traffic management capability .
- For an classic Application Load Balancer, use load-balancing-scheme=EXTERNAL .
```
gcloud compute forwarding-rules create http-content-rule \
        --load-balancing-scheme= LOAD_BALANCING_SCHEME 
\
        --network-tier=PREMIUM \
        --address=lb-ipv4-1 \
        --global \
        --target-http-proxy=http-lb-proxy \
        --ports=80
```

Testing

Note the IPv4 address that was reserved:

gcloud compute addresses describe lb-ipv4-1 \
    --format="get(address)" \
    --global

Test this setup by running:

curl http:// IP_ADDRESS 
?ABTest=A

curl http:// IP_ADDRESS 
?ABTest=B

In a browser, open http:// IP_ADDRESS ?ABTest=A and http:// IP_ADDRESS ?ABTest=B .

Set up HTTP header-based routing

This example demonstrates adding and removing HTTP headers to do intelligent routing.

Before you begin

You can use an existing external Application Load Balancer or create a new one.

You can use this feature with any of the supported backend types . This example assumes that you're using VMs in an instance group.

To set up a simple load balancer, see the query parameter-based example above.

Updating the URL map

Console

The Google Cloud console is currently unsupported for setting up header-based and parameter-based routing. Use gcloud or the API instead.

gcloud

This example demonstrates using HTTP request headers to do A/B testing by matching on values in the request's HTTP headers.

Create a YAML file /tmp/web-map-http.yaml . Replace PROJECT_ID with your project ID.

  defaultService 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-a 
 kind 
 : 
  
 compute#urlMap 
 name 
 : 
  
 web-map-http 
 hostRules 
 : 
 - 
  
 hosts 
 : 
  
 - 
  
 '*' 
  
 pathMatcher 
 : 
  
 path-matcher-1 
 pathMatchers 
 : 
 - 
  
 defaultService 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-a 
  
 name 
 : 
  
 path-matcher-1 
  
 routeRules 
 : 
  
 - 
  
 matchRules 
 : 
  
 - 
  
 prefixMatch 
 : 
  
 / 
  
 headerMatches 
 : 
  
 - 
  
 headerName 
 : 
  
 ABTest 
  
 exactMatch 
 : 
  
 A 
  
 priority 
 : 
  
 0 
  
 service 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-a 
  
 - 
  
 matchRules 
 : 
  
 - 
  
 prefixMatch 
 : 
  
 / 
  
 headerMatches 
 : 
  
 - 
  
 headerName 
 : 
  
 ABTest 
  
 exactMatch 
 : 
  
 B 
  
 priority 
 : 
  
 1 
  
 service 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-b 
 tests 
 : 
 - 
  
 description 
 : 
  
 Test routing for query ABTest with A 
  
 host 
 : 
  
 example.com 
  
 path 
 : 
  
 / 
  
 headers 
 : 
  
 - 
  
 name 
 : 
  
 ABTest 
  
 value 
 : 
  
 A 
  
 service 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-a 
 - 
  
 description 
 : 
  
 Test routing for query ABTest with B 
  
 host 
 : 
  
 example.com 
  
 path 
 : 
  
 / 
  
 headers 
 : 
  
 - 
  
 name 
 : 
  
 ABTest 
  
 value 
 : 
  
 B 
  
 service 
 : 
  
 https://www.googleapis.com/compute/v1/projects/ PROJECT_ID 
/global/backendServices/service-b

Validate the URL map.
```
gcloud compute url-maps validate --source /tmp/web-map-http.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 web-map-http \
   --source /tmp/web-map-http.yaml \
   --global

Testing

Using the IPv4 address of the associated load balancer, test this setup by running:

curl http:// IP_ADDRESS 
-H "ABTest: A"

curl http:// IP_ADDRESS 
-H "ABTest: B"

What's next

Clean up the load balancer setup .

Set up header and query parameter-based routing for the classic Application Load Balancer Stay organized with collections Save and categorize content based on your preferences.

Before you begin

Set up query parameter-based routing

Add two backend instance groups

Console

gcloud

Configuring a firewall rule

Console

gcloud

Reserving an external IP address

Console

gcloud

Setting up the load balancer backends

Console

gcloud

Creating the URL map

Console

gcloud

Creating the target proxy and forwarding rule

Console

gcloud

Testing

Set up HTTP header-based routing

Before you begin

Updating the URL map

Console

gcloud

Testing

What's next

Set up header and query parameter-based routing for the classic Application Load Balancer