The second type of Object in PageSentry is the Notifier. When a Sentry has something to report it hands the task off to one or more Notifiers. To open the Notifier Setup dialog box, choose Add Notifier from the Setup pull-down menu, or click the Create New button in the Object Manager. You may define up to 10 Notifiers in the standard version of PageSentry and up to 100 in PageSentry Pro, and each can be used on any or all of your Sentries. The following section describes the various input fields and configuration options for the different methods that PageSentry uses to alert you to a problem. Figure 11 shows the PageSentry Notification dialog box.

To configure the Notification just fill in the appropriate fields. The Notification has the following options:

Notification Name

The Notification Name is the name of the Notifier that appears in the Object Manager and PageSentry Status Window lists. You can name a Notifier anything you like, since it has no effect on the notification process, but like a Sentry each Notifier must have a unique name. However, you should choose a name that you will be able to easily recognize when viewing a Sentry Configuration window, the Object Manager, or the PageSentry Status Window.

Delay After Initial Failure

The Delay After Initial Failure setting allows you to have a Notifier wait a specified period of time after a Sentry encounters an error before actually sending the e-mail or AppleEvent. During the specified time, PageSentry will continue to test the server, and if it returns to service the Notifier will be disregarded with no e-mail or AppleEvent sent out. There are several potential uses for this feature:

One use is to add an additional level of fault tolerance to your Sentries. By setting the Delay After Initial Failure to a period longer than your Sentry's test period, the delay will cause PageSentry to attempt the test multiple times. The first subsequent test that succeeds, the Notifier will not send an error report. By performing several tests during the delay, servers on slow or "flaky" networks may be monitored with greater tolerance.

Another use is to schedule escalating priorities for Notifiers. For example, you may have two Notifiers, one that sends e-mail to the server's primary support person without delay and another Notifier that sends e-mail to you using a 30 minute delay. When the server fails, the primary support person will be contacted immediately, and if the server isn't quickly fixed, you will be notified shortly thereafter.

A third use is to use a PowerKey Pro to restart a Mac-based server by recycling its power. For example, you could have Notifiers send you an e-mail message and a page (using an AppleEvent-driven paging application) immediately on failure, then wait 15 minutes before restarting the server. With this strategy, you will have time to investigate the server before the power is recycled.

Send "Back Up" Notice

In this context, "Back Up" means the server being monitored is "OK now."Checking this option causes the Notifier to send a second e-mail when the Sentry that had the original failure is testing OK again. "Back Up" notifications will only be performed when a failure notification has been previously sent to report a problem

Mail Notification

PageSentry Notifiers are capable of warning you of a downed Internet server via e-mail. We are all familiar with e-mail and most of us check our e-mail many times throughout the day. However, for PageSentry to work as designed, the following conditions must be met:

1. Your e-mail server must be capable of receiving Internet e-mail.

2. Your e-mail server must deliver queued mail frequently to ensure that you get notifications in a timely manner.

3. Your e-mail client must check for new mail frequently, to ensure timely notification.

If these conditions are not met, PageSentry will not be able to contact you in a timely matter, if at all. The following are descriptions of the fields in the Mail Notification section.

Figure 12 shows an example error message in Eudora Pro sent by a Notifier reporting a failure with a Web server.

Figure 12: Notification by e-mail of an error.

User Address

The User Address field contains the e-mail address of the person receiving the Notification. This should be of the form "mailboxname@yourcom.com."If you are sending mail to an address that does not contain the "@" character between the user name and the host name, you will need to place the "<" and ">"characters around the address, as in "<bitnet!address!VMS!mainframe-2>."

Mail Server

The Mail Server field contains the domain name or IP address of the SMTP server that should be used to send the Notification e-mail. Most SMTP servers allow any client to send the server any piece of mail. The server will simply forward the mail to another (closer) mail server until it reaches its final destination. You should use a mail server designated by your network administrator or service provider. Your mail server will often reside on the machine with a name of the form "mail.yourcom.com".

You may want to enter the IP address of your e-mail server instead of the domain name so that if your DNS server fails PageSentry will still be able to send e-mail notifications.

Mail From

The Mail From field contains the e-mail address from which the Notification will be sent. This address is important in case the e-mail cannot be delivered to the "User Address." SMTP servers will try to route the piece of mail back to this "Mail From"address. It is best to set this to an e-mail address on a different e-mail server than the "User Address," if possible.

The Mail From address should contain the "@" sign or a "<" and ">" pair because some e-mail servers (such as AIMS) require a valid "From" address to accept the e-mail your Notifier will be sending.

AppleEvent Notification

If you put information into both the Mail and AppleEvent Notification fields, both will be sent when the Notification is run. Leave either field blank if you do not want that action to occur. For information about writing applications to receive and process AppleEvents sent from PageSentry, see the "Extending PageSentry Using AppleEvents" section later in this Guide.

The following are descriptions of the fields in the AppleEvent Notification section.

Application

This field contains the name of the application to which the AppleEvent is sent. It, or an alias, must be in the same folder as PageSentry. The filename should be the same as it appears in the Finder, with file and folder names separated with colons (":").

"Extra" Info

The "Extra" Info field contains room for a text message that is to be sent in the AppleEvent. Different applets will want different values in this field. Check the documentation of the applet or application to which you are sending the event.

Your PageSentry packages comes with several sample AppleScript Applet examples, including DisplayDialog. See the Read Me files that accompany each applet for information on using them with PageSentry.

Schedule Area

The last area on the notification editor window is the Schedule Area, where each grid square represents one hour. This grid allows you to define when the Notifier is "on call". Click in the boxes to toggle the state for that hour of that day, or click and drag to change multiple cells at once. When a Notifier is executed by a Sentry, the schedule is checked against the current system time and day of the week. If the hour is selected (red), then the e-mail and/or AppleEvent is sent. If the hour is not selected (gray), then no action is taken for that Notifier.

Note that each Sentry can have multiple notifications attached to it, so that other notifications may be sent, even if one Notifier's schedule does not match. You can make a staggering assortment of Notifiers for different people during lunch, weekends, Friday afternoons (whatever), and attach them all to the same Sentry. This Sentry would then send failure notification to different people or applications depending on when the failure occurred.

In Figure 11, the user "someone@somecompany.com" will be contacted via e-mail by "MyNotifier" during the hours of 9:00 AM through 5:00 PM, Monday through Friday, if a Sentry fails.