What is a Sanity Check Plugin?
AlwaysUp and
Service Protector are
both designed to keep your applications functioning 24/7. While they can monitor and take action when a wide range of events occur (for example, your program uses too much RAM or CPU), not all
failure detection capabilities are built in. For example, if your program doesn't operate correctly when another program has stopped, there is no way for AlwaysUp or Service Protector to find about the special relationship and
stop/restart your application.
Fortunately both AlwaysUp and Service Protector can be extended to "plug in" your own arbitrary, failure detection logic. All you have to do is supply an executable (or batch file) that can detect the failure and communicate that
situation to AlwaysUp or Service Protector via a return/exit code. We call these small, targeted failure detection programs "Sanity Check Plugins".
A Sanity Check Plugin can be an executable written in any language (C++, C#, VB, Delphi, etc.) or can be a DOS batch file. The only requirement is that it exits with a special code.
Feel free to construct your own plugins, specific to your situations, or simply use one that we have already written (below).
Available Sanity Check Plugins
We have developed a few Sanity Check Plugins that can be used freely. Each will signal AlwaysUp or Service Protector to:
 Stop/restart your application if a specified program is not running
Command Line Usage
CheckProgramIsRunning.exe <program-name>
where
<program-name> is the name of an executable, as seen in Task Manager
Example
To check if Microsoft Word is running, use:
CheckProgramIsRunning.exe winword.exe
Downloads
CheckProgramIsRunning.exe (490 KB)
Stop/restart your application if a particular file has not changed for a while
Command Line Usage
CheckFileChanged.exe <file-name> <num-minutes> [-v]
where
<file-name> is the full path to the file to be checked (be sure to enclose in quotes if the path contains spaces)
<num-minutes> is the number of minutes
-v signals to produce verbose output (optional)
Example
To check if a log file located at C:\myserver\log.txt has not been modified for the past 10 minutes:
CheckFileChanged.exe "C:\myserver\log.txt" 10
Downloads
CheckFileChanged.exe (529 KB)
Stop/restart your application if a specific web site/URL is not responding
Command Line Usage
check-web-server.bat
Configuration
- Download our free http-ping executable and place it in a new directory
- Download the Sanity Check batch file and place it in the same directory
- Open the batch file in a text editor and modify it to:
- specify the URL to your web server (instead of http://localhost:80)
- set the path to http-ping.exe to point to the location where you saved it
Downloads
http-ping.exe (406 KB)
check-web-server.bat (1 KB)
Special Command Line Parameters
AlwaysUp and Service Protector are able to pass your Sanity Check Plugins one or more "special" values. Compose your command line with the appropriate string and AlwaysUp/Service Protector will make the substitution before invoking your program.
| Replacement String |
Replaced With |
| $ALWAYSUP_PID |
The program identifier (PID) of your running application/service. This can be seen in the Task Manager. |
| $ALWAYSUP_EXENAME |
The name of the executable run to invoke your application. (Just the name, not the full path.) |
| $SERVICEPROTECTOR_PID |
The program identifier (PID) of your running service. This can be seen in the Task Manager. |
| $SERVICEPROTECTOR_SERVICENAME |
The name of the service being protected (the short name). |
For example, to have AlwaysUp pass your Sanity Check program the application's program identifier (PID), then your command line might resemble this:
C:\myserver\my_check.exe $ALWAYSUP_PID
If your main application is running with PID 563, then your plugin program will be invoked like this:
C:\myserver\my_check.exe 563
A Sanity Check Plugin can be an application written in any language (C++, C#, VB, Delphi, etc.) or can be DOS batch file. The only requirement is that it exits with a return code of:
- 0 when the check succeeds;
- 1 when the check fails and the application should be stopped and restarted as you have configured;
- 10 when the check fails and the computer should be rebooted;
- 100 when the check fails and your application should be stopped and not restarted;
- any other value when the check fails due to an error independent of the application being monitored (such as an error internal to the utility), or to simply indicate failure without causing a restart.
In the last case, the application is not restarted but a message is written to the event log (and an email is sent if so configured).
Note that if the Sanity Check plugin fails to complete in 120 seconds, the application will be restarted.
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Sanity Check Plugins