Learn how HAProxy ACLs work with Regex. Our HAProxy Support team is here to help you with your questions and concerns.

How do HAProxy ACLs with Regex Work?

Did you know that HAProxy has a feature known as ACL that lets us define conditions or rules to control how incoming traffic is processed and routed to different backend servers?

ACL is short for Access Control List. It is often used for tasks like request routing, access control, and traffic manipulation.

Furthermore, HAProxy ACL regex refers to the use of regular expressions (regex) within ACLs to match patterns in incoming requests.

Let’s take a look at how HAProxy ACLs with regex work:

ACLs in HAProxy are usually defined in the configuration file with the ACL keyword. Additionally, these ACLs are named and assigned conditions according to different criteria.

For example:
acl is_example_host hdr(host) -i example.com

Here, we define an ACL named is_example_host that checks if the Host header matches “example.com” case-insensitively.

Additionally, regular expressions can be used in ACLs to match more complex patterns. Furthermore, we can use the ACL keyword along with the if statement to define ACLs with regex patterns.

For example:
acl is_product_page path_reg ^/products/[^/]+$

Here, the ACL is_product_page uses a regular expression (path_reg) to match URLs that start with “/products/” followed by one or more characters that are not slashes.

Then, after we define ACLs, we can use them with frontend or backend configuration to make decisions based on the ACL conditions.

For example, we can use ACLs to route traffic to different backend servers, apply request/response rules, or perform access control.

use_backend product_servers if is_product_page

Here, the use_backend directive routes traffic to product_servers if the is_product_page ACL condition is met.

By using regular expressions in HAProxy ACLs, we gain greater flexibility in matching and handling incoming traffic patterns.

This comes in handy for complex routing and load balancing where we need to direct traffic according to dynamic content or specific URL structures.

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Conclusion

In brief, our Support Techs demonstrated how HAProxy ACLs work with Regex.