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You can set up health tests, or probes, that can be run for each real server associated with a virtual server. These probes help you monitor the health of servers. This chapter contains the following sections:
Probes are configurable health tests that you can tailor to a particular Web server. Each step in a Web server probe makes a specified HTTP request to the server and evaluates the response based on user-defined success criteria. You can specify that upon probe failure, the server is taken out of service, or that it generate a warning through the LocalDirector User Interface notification mechanism. Probes can be run automatically by a user-specified schedule on all of the real servers under a virtual server, or manually by the user on a particular real server. Each probe step can test the following items for a particular URL on a server:
LocalDirector User Interface helps you create the steps of a probe with an easy-to-use wizard. The first few steps establish required information, including the name of the new step and the characteristics of the URL to be probed. After you set up this initial information, clicking the Finish button completes the remainder of the probe step creation with default values.
A default probe step has the following values in addition to a name and URL:
Follow this procedure to create a probe with default values. At many points during the dialog, clicking Test will test the probe (see the section "Checking the Status of a Probe" later in this chapter).
Step 1 Right-click on the virtual server to which you are adding the probe.
Step 2 Select Add Probe from the resulting drop-down menu. A window similar to Figure 6-1 displays.
Follow these steps to identify the new probe:
(a) In the Name field, type an identifying name for the probe.
(b) In the Default Probe Port field, type a port number as necessary. If the virtual server of the probe has a port number, that port number appears in this field and is noneditable. If the virtual server of the probe does not have a port number, the default port number for the service type (such as 80 for a Web service type) appears in this field and is editable. If any of the real servers that this probe runs on are nonport bound, the probe tests them using the port number entered in this field.
(c) At the bottom of the Probe Steps field, click the Add Step button. This brings up the Create Probe Step window.
Step 3 The Create Probe Step window requires you to name the probe step and define the action of the probe if the step fails. Figure 6-2 illustrates this window.
Follow these steps to create a probe step:
(a) At the Step name field, type the name of the step.
(b) Check the box below this Step name field if you want the probe to continue in the event that the step fails. Leave this box empty if you want the probe to stop immediately if this step fails.
Step 4 Click Next.
The next window in the Create Probe step series displays as illustrated in Figure 6-3.
Step 5 This window lets you define the characteristics of the URL to be tested.
(a) At the URL field, type the URL to be tested.
This URL is normally an absolute path specification with no host or port information (for example, /index). The LocalDirector User Interface validates the URL specification as you enter it. After it accepts a correct URL syntax, the LocalDirector User Interface extracts the host and port information from the properties of the real server on which the probe runs.
(b) In the Command area, select either the GET or POST method, depending on what your Web server is expecting requests to come in as. This is the command execution that is tested by the probe step.
(c) In the SSL Support area, check the Communicate with server via SSL box if you are using HTTPS; otherwise leave the box empty.
(d) As necessary, enter the set of URL parameters that further define the URL. In standard URL syntax, the parameters are the keyword=value pairs that appear after the question mark (?), separated by ampersand (&); for example:
?query=webspective&list=10.
Step 6 At this point, you can allow LocalDirector User Interface to complete the probe with default values for the remaining step parameters. Click Finish to complete the probe step creation.
You are returned to the Create New Probe window. Repeat Steps 1 through 5 to create other steps for this probe.
Step 7 In the area on the right side of the Create New Probe window, select the schedule for the probe to run. You can select a daily, hourly, or by-the-minute schedule, or you can specify that the probe be run manually. By default, the probe is run once an hour. In general, you will want to schedule a probe to run automatically so that tests can be run in the background. If you configure a probe to run manually, see the section "Running a Probe Manually" later in this chapter for a description of how to run the probe.
Step 8 If the real server is to be taken out of service upon probe failure, leave the Out of service on failure box checked. Otherwise, uncheck the box.
Step 9 Click OK.
You now have a probe that you can use to test the health of your Web server. See the section "Checking the Status of a Probe" later in this chapter for a description of how to manually run a test.
The previous section described how to set up a probe with default settings. This section describes how to set up a probe with optional nondefault settings. At any time during the probe creation, clicking the Finish button assumes that any probe characteristics that have not been specified will have the default settings, as described in the section "Creating Minimal Probes" earlier in this chapter.
Follow this procedure to create a probe with nondefault values. At many points during the dialog, clicking Test will test the probe (see the section "Checking the Status of a Probe" later in this chapter).
Step 1 Perform Steps 1 through 5 in "Creating Minimal Probes" earlier in this chapter.
Step 2 Click Next to further define the step creation. The window in Figure 6-4 displays.
Step 3 In this window, you specify the execution time limit boundaries within which the probe must execute.
(a) At the minimum execution time limit text field, specify the minimum execution time in seconds or minutes. Select the appropriate unit of time.
(b) At the maximum execution time limit text field, specify the maximum execution time in seconds or minutes. Select the appropriate unit of time.
Step 4 Click Next to further define the step creation.
The window in Figure 6-5 displays.
Step 5 This window (see Figure 6-5) allows you to test servers when cookies are present in the request. Allowing applicable cookies to be sent enables the LocalDirector User Interface to simulate a real transaction for testing. By default, all applicable cookies returned in the responses to previous steps of this probe will be sent. No additional new cookies will be sent.
(a) Click the first checkbox to specify that all applicable cookies returned in the responses to previous steps of this probe are to be sent.
(b) Click the second checkbox to specify that an arbitrary set of new cookies (specified as cookie name/value pairs) are to be sent.
Step 6 Click Next to further define the step creation.
The window in Figure 6-6 displays.
Step 7 This window (see Figure 6-6) allows you to specify a particular user agent (such as a browser type) that the probe can simulate when making the request to the server. If you do not specify a user agent here, the request identifies the user agent as being the LocalDirector User Interface server.
(a) Select a browser type from the drop-down list of common browser types (such as Microsoft Windows Internet Explorer 4.0, or Netscape Communicator 4.0.1). (The LocalDirector User Interface automatically maps the selected browser type to the corresponding user agent string.) Select Other to enter your own user agent string. See Figure 6-7.
(b) As necessary, type an arbitrary user agent string to be sent verbatim in the request. You can use this option to simulate arbitrary browsers that are not one of the common browser types offered in the drop-down list or to tailor a user agent string for your particular browser.
Step 8 Click Next to further define the step creation.
The window in Figure 6-8 displays.
Step 9 This window (see Figure 6-8) allows you to specify whether access to the requested URL is protected by an HTTP basic authentication scheme.
(a) If the URL is not protected by any authentication scheme, select None in the Authentication Method field. Click Next.
(b) If the URL is protected by HTTP basic authentication, select HTTP Basic Authentication. Choosing this list item enables the lower portion of this dialog so you can provide:
Step 10 Click Next to further define the step creation.
The window in Figure 6-9 displays.
Step 11 This window (see Figure 6-9) allows you to specify the behavior of the probe step when it encounters certain status codes.
(a) In the Redirection Status Code Handling area, specify how a 301 (permanent redirection) status is to be treated. By default, the LocalDirector User Interface treats this status as unacceptable.
(b) In the Redirection Status Code Handling area, specify how a 302 (temporary redirection) status is to be treated. By default, the LocalDirector User Interface treats this status as unacceptable.
(c) In the OK Status Code Handling area, specify that a 200 (success) status is to be treated as acceptable (checkbox is checked) or unacceptable (checkbox is unchecked). By default, the LocalDirector User Interface treats this status as acceptable.
(d) In the Other Successful Status Codes area, type any other arbitrary status codes (as integers) that are to be treated as acceptable. An example of an arbitrary status code is one that might be returned by custom code running on your Web server. If you do not specify additional status codes here, the LocalDirector User Interface will treat any status codes other than 301, 302, and 200 as unacceptable.
Step 12 Click Next to further define the step creation.
The window in Figure 6-10 displays.
Step 13 This window (see Figure 6-10) allows you to define an acceptable length for the content returned by the probe. By default, the content length is ignored. You can specify one of the following behaviors:
Step 14 Click Next to further define the step creation. The window in Figure 6-11 displays.
Step 15 This window (see Figure 6-11) allows you to specify the acceptable content (MIME) type that can be returned by the request. By default, the content type is ignored. Click one of the following buttons.
Step 16 Click Next to further define the step creation.
The window in Figure 6-12 displays.
Step 17 This window (see Figure 6-12) allows you to specify any particular character strings the content returned by the request either should contain or must not contain. By default, no constraints are placed on the character strings that can be present in the returned content.
For each character string you enter, click either the Must Contain or Must Not Contain checkbox, as desired.
Step 18 Click Next to further define the step creation.
The window in Figure 6-13 displays.
Step 19 This window (see Figure 6-13) allows you specify that particular cookies must be returned in the request response. By default, no constraints are placed on the cookies contained in the request response.
For each cookie entry, click to check or uncheck the Ignore Value checkbox according to the following:
Step 20 Click Finish to complete the probe step creation. You are returned to the Create New Probe window. Repeat Steps 1 through 20 to create other steps for this probe.
Step 21 At the right side of the Create New Probe window, select the schedule for the probe to run on. You can select a daily, hourly, or by-the-minute schedule, or you can specify that the probe be run manually. By default, the probe is run once an hour. In general, you will want to schedule a probe to run automatically so that tests can be run in the background. If you configure a probe to run manually, see the section "Running a Probe Manually" later in this chapter for a description of how to run the probe.
Step 22 If the real server is to be taken out of service upon probe failure, leave the Out of service on failure box checked. Otherwise, click to uncheck the box.
Step 23 Click OK.
You now have a probe that you can use to test the health of your Web server.
Follow this procedure to add or delete steps from any probe:
Step 1 Select the probe to be edited from the Tree view in the LocalDirector User Interface main window.
Step 2 Select the Edit menu Properties of probe name option from the toolbar (or right-click Properties). The Edit Probe window displays (it is the same window as the Create Probe window).
Step 3 To add another step to this probe, click the Add Step button. The dialog for this is identical to that described in the "Creating Minimal Probes" and "Creating Advanced Probes" sections earlier in this chapter.
Otherwise, if you want to remove a probe step, select that step and click the Delete Step button. At the main Create Probe window, you can also move the order of a step up and down to change the sequence of the probe step execution by using the arrow icons to the right of the probe step list.
You can change the properties of any probe step using the Edit Web Probe Step window (see Figure 6-14). This window consists of a series of tabs; each tab logically organizes the probe step parameters into a number of categories. For a further description of these parameters, refer to the step creation dialog described in the section "Creating Advanced Probes" earlier in this chapter. lists the properties for Web steps.
| Tab | Properties |
|---|---|
General |
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Basic Request Parameters |
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Other Request Parameters |
|
Response Content Requirements |
|
Response Status Code Requirements | Status code handling |
Other Response Requirements |
|
Follow this procedure to change the properties of any probe step:
Step 1 From the Tree view on the main LocalDirector User Interface window, select the probe whose steps are to be edited.
Step 2 Select the Edit menu Properties option (or right-click on the probe). The Edit Probe window displays.
Step 3 In the Probe Steps area, select the step to be edited.
Step 4 Click the Edit button (or double-click on the step).
The Edit Web Probe Step window displays (see Figure 6-14).
Step 5 Select the appropriately named tab to edit the desired step property.
Step 6 Click OK.
Step 7 Click OK at the Edit Web Probe window (or optionally, edit another step).
The method described in the first bullet runs the probe on one or more real servers. The results are reported for the real servers that the probes were run on. The method described in the second bullet runs the probe on one real server. The methods described in the third and fourth bullets are actually tests of the probe itself. In these instances, the probes are run against particular real servers, and the main focus of the results is reports about the steps in the probe run. See the section "Testing the Probe" later in this chapter for further details.
The status of a probe run is displayed in the Probe Status area, which is described in the section "Checking the Status of a Probe" later in this chapter. The Probe Status area displays the current state of the probe if it is running, or the state of the last run. Details of a probe run are displayed in the Probe Details popup window.
The LocalDirector User Interface displays any error messages resulting from the probe run in the Message area. This area has a table with entries for each probe error message. See the chapter "Working with Messages" later in this guide for a description of how to look at and acknowledge probe run messages.
Once a probe is set up to run automatically, it begins running on its assigned schedule. The probe runs on every real server that is in service under the virtual server of the probe. If you find that you need to run the probe manually in between scheduled runs, see the section "Running a Probe Manually" later in this chapter.
To manually run a probe, right-click on a probe instance in the Probe Status area. This action selects that table cell and brings up the following probe popup menu (see Figure 6-15):
The popup menu allows you to run a probe from the main LocalDirector User Interface window. The following options are available from the popup menu:
Step 1 In the Probe Status area, right-click on the cell corresponding to the real server and probe to be run. A probe popup menu displays (see Figure 6-16).
Step 2 From the resulting popup menu, select Run Now. The probe is run on the real server listed in the real server column for that probe entry.
Look for any errors for the probe run of that real server. The status of the probe run is indicated in the Probe Status area, and any error messages that the system returns appear in the Message area.
Once you take a real server out-of-service (OOS), its associated probes will not run on automatic schedules. (If the LocalDirector User Interface takes a real server OOS, probes do continue to run.) A probe can run automatically only on an In service real server. See the section "Running a Probe Manually" earlier in this chapter for a description of how to manually run a probe.
Testing a probe runs that probe on a particular real server that you specify. A probe can be tested at several stages:
When you click the Test button for a probe, a dialog similar to that shown in Figure 6-17 displays. If there are multiple real servers, follow this procedure to choose which real server to run the test on:
Step 1 By default, the LocalDirector User Interface expects you to define the name of the real server where the probe is to be tested.
Step 2 Click OK.
Probe tests do not result in any information in the Probe Status area. Instead, a dialog displays immediately showing the results of the test.
The LocalDirector User Interface server maintains the current status of a probe in the Probe Status area, located below the Server Details area. This area displays status information about probes for the selected virtual server, presented as a table with real servers as columns and probes as rows. The intersection of a probe and a real server is a cell. Each cell has the following status indicators (see Figure 6-18):
Double-clicking on any cell to the right of the first column in the Probe Status area displays the detailed status of all the steps in a probe. For example, Figure 6-18 illustrates the cell for the probe pr2 for the real server real3. Double-clicking on that cell displays the associated Probe Details popup window, as illustrated in Figure 6-19. The left column of this table lists all the steps in the probe, and the right column displays the status of each probe step. If the probe step failed, this failure is also detailed.
The Probe Details popup window also provides detailed descriptions of any probe step failures. Select a step on the left to see the details in the right side of the window. If a probe completes with a warning or failure, the LocalDirector User Interface Message area also displays a simple notification of the probe failure. See the chapter "Working with Messages" later in this document for more information.
 | Caution If you delete a real server that you have run probes against and undo the deletion, the LocalDirector User Interface does not reinstate the earlier probe results. All probe status information is lost until the next time the probe runs. |
From the Probe Status area, you can also manually run a probe for a particular real server. Refer to the section "Running a Probe Manually" earlier in this chapter for a description.
Posted: Wed Sep 22 20:43:18 PDT 1999
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