Learn how to use HAproxy Backend ACL. Our HAproxy Support team is here to help you with your questions and concerns.

HAproxy Backend ACL

HAProxy plays a huge role when it comes to load balancing and proxying. One of its key features is Access Control Lists (ACLs). It enables administrators to define conditions as per different attributes and make routing decisions or apply specific rules to different types of traffic.

When it comes to HAProxy backends, ACLs play a key role in determining which backend should handle a particular request based on certain conditions. Let’s take a look at how we can use HAProxy backend ACLs to streamline our traffic routing.

1. The first step in utilizing HAProxy backend ACLs is defining the ACLs. This is done with the `acl` keyword followed by a name and a condition. These conditions can be based on factors like headers, paths, source IP addresses, or any other attributes that HAProxy can inspect.

   acl acl_name condition

   For example, we can create an ACL based on a specific path:

   acl is_blog path_beg /blog


2. Then, it is time to employt he ACLs to direct traffic to specific backends using the `use_backend` directive. This directive lets us route requests as per the conditions in the ACLs.
   use_backend backend_name if acl_name
   For example, we can route requests to a backend named “blog_backend” if the path begins with “/blog”:

   use_backend blog_backend if is_blog
3. Now it is time to define the corresponding backends. Backends specify where the traffic should be sent based on the ACL conditions.

   backend backend_name
mode <mode>
server server_name server_address:server_port


   For example:

   backend blog_backend
mode http
server blog_server_1 192.168.1.10:80
server blog_server_2 192.168.1.11:80


A Complete Example

Let’s put it all together with this example:

# Define ACL based on the path
acl is_blog path_beg /blog
# Use ACL to route traffic to the appropriate backend
use_backend blog_backend if is_blog
# Define the backend for blog traffic
backend blog_backend
mode http
server blog_server_1 192.168.1.10:80
server blog_server_2 192.168.1.11:80


In this example, requests with paths starting with “/blog” will be directed to the “blog_backend,” while other requests will follow default rules or other ACLs.

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Conclusion

In brief, our Support Experts demonstrated how to use HAproxy Backend ACL.