Setting HTTP Redirection Threshold Levels
ClusterCATS gives you the ability to set the threshold at which a server goes into a busy state and begins redirecting all user requests to other available servers in the cluster. There are two redirection thresholds you can configure with ClusterCATS:
- Load threshold
- Gradual redirection threshold
You configure these threshold levels so that as a server approaches a certain load level, requests are redirected to other servers in the cluster based on their availability.
You can set these two threshold levels to be very close to ensure that your server availability remains at a very consistent level. Or you can set your load redirection and gradual redirection thresholds far apart, allowing your server to handle wider acceptable levels of traffic.
Much of your redirection threshold configuration decisions hinge on the architecture of your application and where the bulk of your processing resources need to be allocated.
Load threshold
The load threshold defines when the server's state transitions from available to busy. When the load exceeds the threshold that you configure, all user requests are redirected to other servers in the cluster, based on their own availability.
Gradual redirection threshold
Gradual Redirection lets you set a secondary threshold at which user requests begin being redirected. If the Gradual Redirection threshold is set close to the Redirection threshold, then a greater portion of user requests are redirected. If it is set further away from the Redirection threshold, then fewer requests are redirected.
To configure gradual redirection using the Server Load dialog:
- Select one of the servers or select the cluster in the left pane of the Explorer.
- Right click on one of the server icons. Select Monitor > Load. The Server Load dialog box displays.
- Grab the Red Load Threshold line with the cursor. Move the red line up or down to reset the server's load threshold level. As you move the line, the load threshold percentage changes.
To configure gradual redirection using the Server Properties dialog:
You can also set this number on the Access tab of the Server Properties box.
- Right click on the Server icon.
- Select Configure > Access. The Properties dialog appears for the current server, with the Access tab selected.
- In the Load Balancing section, enter a load number at which you want the server to start redirecting user requests.
To set up gradual redirection:
- Select one of the servers or select the cluster.
- Right click on one of the server icons. Select Monitor > Load. The Server Load dialog box displays.
- Click on the Gradual Redirection threshold in the lower left-hand corner of the box. A yellow line appears below the red line. This is the Redirection threshold line. Grab the yellow Load Threshold line with the cursor. Move the yellow line up or down to reset the server's gradual redirection start point. Notice the number in the lower left-hand corner of the dialog box. It changes to a % as you move the line. The closer you move the line to the red line, the more redirects occur. The further you move the line away from the red line fewer requests are redirected.
You can also set this number on the Access tab of the Server Properties box.
- Right click on the Server icon
- Select Configure > Access.
- In the Load Balancing section, click on Gradual Redirection and plug in a load number at which you want the server to start gradually redirecting user requests.
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