The core steps to implement load balancing using IIS ARR to build a server farm include: 1. Install and enable IIS ARR, 2. Create a server farm and add back-end nodes, 3. Set up a load balancing algorithm and health check policies, 4. Configure URL rewrite rules for traffic forwarding. First, you need to manually install the ARR module through the server manager and enable the proxy function to support reverse proxy; at the same time, make sure that the URL rewrite module is installed. Then create a server farm in the IIS management interface, add the backend server address and confirm that its status is normal. Then select the appropriate load balancing algorithm based on the needs, such as polling, weighted polling, or minimum request count, and customize the health check path, timeout, failure threshold, and check interval for improved stability. Finally, configure the URL rewrite rules to match and forward the request to the corresponding server farm, and retain the original Host header information if necessary to avoid request errors. During the entire process, you need to pay attention to the firewall settings, health check path availability and the accuracy of rewriting rules.

If you want to know how to use IIS ARR to build a server farm to achieve load balancing, there are actually a few steps: configuring ARR, setting up a server farm, choosing a suitable load balancing algorithm, and adding health checks. Although these operations are not complicated, the details are prone to errors. Let me talk about how to do it from the perspective of actual deployment.

Install and enable IIS ARR

First, you must confirm that Application Request Routing (ARR) is installed on your server. This function is not enabled by default and needs to be added manually. You can install it by ticking ARR in the optional components of IIS by "Server Manager" → "Add Roles and Features".

After the installation is complete, open the site or server node in IIS Manager, find the "Application Request Routing Cache" module, and click the "Enable Agent" button. This step is critical, and if not enabled, ARR cannot work as a reverse proxy.

In addition, ARR relies on the URL rewrite module, so make sure that the URL Rewrite extension is also installed. Otherwise, you will encounter problems when configuring forwarding rules in the subsequent configuration.

Create a farm and add a backend node

There is a "Server Farms" at the bottom of the tree structure on the left side of the IIS management interface. Click to enter to create a new server farm. Give it a name, such as app-servers.

After creation, right-click the server farm, select "Add Server", and enter the address of each backend server you want to load, such as http://ipnx.cn/link/c57330a3a53f27a63f881d14065f4c46 or host name. After each server is added, ARR will try to do a health check by default.

It should be noted here that the status of each backend server may be displayed as "online" or "offline". If the status is wrong, first check the network connectivity and whether the target server responds to the request normally.

Set up load balancing algorithms and health check strategies

ARR provides several commonly used load balancing algorithms:

• Round Robin : Most commonly used, equally allocate requests.
• Weighted Round Robin : Suitable for servers with different performance.
• Least Requests: Send new requests to the server with the lowest number of requests.

You can select the appropriate method in the "Load Balance" setting of the server farm.

Regarding health checks, it is recommended not to use the default settings. The default is to ping the backend server's root path / every few seconds, but this may affect performance or return a non-200 response. It is recommended to customize a path specifically for health checks, such as /healthcheck , and set a reasonable failure threshold and interval.

For example:

• Set the path to /healthcheck
• Response timeout is set to 5 seconds
• The number of failures reaches 3 times and then marked as offline
• Check interval is set to 30 seconds

This not only ensures stability, but does not put too much pressure on the back end.

Configure URL rewrite rules for traffic forwarding

The final step is to have ARR transfer the request to the farm correctly. You need to open "URL Rewrite" under the site and add an inbound rule.

The basic approach is:

• Match paths, such as /*
• Use the operation type of "Send request to ARR farm"
• Select the server farm you just created

Note that the matching rules here should be adjusted according to actual needs. For example, if you want to forward /api/* only to a specific server group, you can set the mode to ^api/(.*) and then add the corresponding path stitching logic to the rewrite part.

In addition, sometimes the original Host header information needs to be retained. At this time, the incoming Host field should be set to {HTTP_HOST} in the "Rewrite HTTP Request Header", otherwise the backend service may return an error due to the host mismatch.

Basically these steps. The whole process seems simple, but the common problems encountered in actual deployment include firewall interception, blocked health check paths, and URL rewriting rules not taking effect. As long as you investigate step by step, it can generally be solved.

The above is the detailed content of Setting Up Server Farms for Load Balancing with IIS ARR. For more information, please follow other related articles on the PHP Chinese website!