Server Load Thresholds

ClusterCATS makes certain that your Web applications remain available and running at optimum performance by intelligently managing the amount of HTTP traffic hitting your clustered servers. By setting load thresholds on each server in your cluster, you can control and manage your site's availability and performance. Many of your threshold configuration decisions hinge on your site's architecture and where the bulk of your processing resources need to be allocated.

During an HTTP redirection, ClusterCATS evaluates the cluster's state according to HTTP server state first, and then ColdFusion server load. This policy is the same in both centralized and distributed ClusterCATS configurations. In a centralized ClusterCATS cluster with all Web servers at one site, ClusterCATS only redirects if the server is busy or restricted.

For each cluster member, you configure two load thresholds:

By default, the Peak load threshold is 90% and the gradual redirection threshold is 10%. These default settings adequately handle HTTP traffic going across most Web sites. However, if your Web site is particularly processing intensive, you should lower both threshold settings to better accommodate the increased load.

If you want the server to be able to handle as much load as possible, set both threshold values close to one another. However, if you want redirection to occur well in advance of the server nearing its peak threshold, set the values farther apart so that there is a differential of at least 10% between the two threshold values.

This section shows you how to set the peak and gradual redirection load thresholds for ClusterCATS servers in the following sections:

Configuring load thresholds in Windows

To adjust load thresholds for a cluster member:

  1. Open the ClusterCATS Explorer and select a server.
  2. Select Server > Properties. Alternatively, you can right-click the server and select Properties.

    The server's Properties dialog box appears:

  3. Select the Load tab.

  4. Enter a new numeric value (less than 100%) in the first Load Management field. This is referred to as the Peak load threshold. In the example above, the Peak load threshold is set to 90.
  5. Enable the Gradual Redirection check box.
  6. Enter a new value in the Gradual Redirection field. This value must be lower than the Peak load threshold.
  7. Click OK to apply your new threshold settings.

Viewing a cluster's load status

ColdFusion reports its load data directly to ClusterCATS. Consequently, you can view the load on the ColdFusion servers at any time using the Server Load Monitor.

To view your cluster's current load levels:

  1. Open the ClusterCATS Explorer and select a cluster.
  2. Select Monitor > Load. Alternatively, you can right-click the cluster you have selected and select Monitor > Load.

    The Server Load dialog box appears and displays the current load status for each cluster member in the cluster you selected.

    The load monitor shows three lines:

Adjusting load threshold settings graphically

You can view and set threshold settings of an individual cluster member using the Server Load Monitor's visual display. To set or change threshold settings using this method, use your mouse to drag the Peak (red) and Gradual Redirection (yellow) threshold lines to their desired settings instead of entering numeric values in fields, as you do in the server Properties dialog box.

To configure load threshold settings using the Server Load dialog box:

  1. Open the ClusterCATS Explorer and select a server.
  2. Select Monitor > Load. Alternatively, you can right-click the server and select Monitor > Load.

    The Server Load dialog box appears:

  3. Use your mouse to drag the Peak load threshold (red) up or down.

    As you move the line, the Peak load threshold percentage changes.

  4. Enable gradual redirection by selecting the Gradual Redirection check box.
  5. Drag the Gradual Redirection load threshold (yellow) to adjust it accordingly.
  6. Close the dialog box to apply the load threshold settings you configured.

Configuring load thresholds on UNIX

To configure load thresholds for a cluster member:

  1. Open the ClusterCATS Web Explorer if it is not already open.
  2. Click the Show Cluster link.

    The Show Cluster page appears:

  3. Enter the fully qualified host name of a server in the Web Server Name field.
  4. Click OK.

    The Cluster Member List page appears, as the following figure shows. If you get an "Error: Server <cluster_member_name> could not be found" message, make sure you used the correct, fully-qualified server name and that the server is running.

  5. Click the Server Attributes link.

    The Connect To Server page appears:

  6. Select the server you want to connect to from the Web Server Name listbox.
  7. Click OK.

    The selected server's Server Properties page appears:

  8. Click the Administration link under Server Attributes.

    The Server Administration page appears for the selected server.

  9. To change the Peak load threshold, enter a new numeric value (less than 100%) in the Standard Load Threshold field.
  10. Enable the Gradual Redirection check box if it is not already enabled.
  11. To change the Gradual Redirection load threshold, enter a new numeric value in the Gradual Load Threshold field. This value must be lower than the Standard Load Threshold.
  12. Click OK to apply your new load threshold settings.