Drop Shadow

How It Works

The system notices page is designed to display important system notices both during normal operations and during emergencies. It is designed to rely on as few systems as possible so that even as systems go down around it, system notices can be added and displayed. As long as the web server is running, the system notices should be displayed. As long as the web server is running and able to start new processes, system notices can be added.

Where do system notices appear?

  • All notices appear on the system notices page and RSS feed.
  • A notice will also appear on the ITS page and the its-faculty-log mailing list if one of its display categories is “critical” .

Wide availability

System notices may be viewed through an the system notices web page or on the RSS feed available there. Critical notices will be sent to the mailing list its-faculty-log. Individual notices will also appear on other appropriate web pages, depending on their category. For example, notices about student schedules will appear on the schedule, roster, and class search pages.

New critical notices are checked for on the hour and half hour mark, and sent to the mailing list if not already sent.

Multiple means of serving notices

The normal means of creating a notice will be to use the web interface. If the web interface is unavailble but the command line on the web server is not, either of the ITS web accounts can use /usr/local/bin/notice to add a notice. This may be useful if the web server is working but not allowing CGIs, or if web services are unavailable but the server can still send mail to the mail server for ultimate distribution to the mailing list.

Notice retention

The system is designed for important, on-the-spot notices and warnings. Submitters are allotted a short (30 minute) period during which minor mistakes may be corrected. However, major content, even if later investigation proves it wrong, should not be removed; rather a later notice should update that information.

Changing past notices is likely to cause confusion and perhaps even resentment among members of our community who might see it as “changing history” or hiding known problems. Incorrect guesses often shed light on other issues that need to be addressed.

We should only remove messages that are utterly inappropriate and confusing to our community. But we should be careful not to confuse “embarrassing to ITS” with “confusing to our community”. If we do not own our mistakes, we will repeat them.

Filesystem database

The data is stored in a sqlite3 database. SQLite differs from other database servers in that the databases are accessed as a local file. The system thus needs no network connection to an external database server. All it needs is access to the local filesystem. Even if the network around the web server goes down or becomes unreliable, as long as the web server itself is available it will have access to the system notices database.

RSS and HTML Caches

The major category feeds (all, critical) are cached to the file system. Even if network slowdowns cause the web server to build up too many processes or available memory is too low to read from the database, the server will still be able to display all notices from before the limit was reached.

Automatic ITS employee list

Twice a week, the system downloads from ldap.sandiego.edu a list of all ITS employees from the on-line phonebook in the following departments:

Academic Computing Services, Admin Information Services, Desktop Support, Information Tech Services, Network and Systems Operations, Telecommunications

Any of these employees automatically have access to add system notices. There is no need for a supervisor to contact the webmaster, and no ITS employee should discover during a critical moment that their supervisor has not yet done so.

Authentication fallback

Under normal conditions the system notices page uses the single sign-on system to allow any ITS employee to add system notices. If the single sign-on system or if the central authentication system become unavailable, the system notices add form will devolve to a backup of ITS users from the last ITS user download (see above). If the ITS employee needing to add a notice has changed their password within the last week, they may need to use their old password to upload their notice. But their access will not be cut off even if the authentication system is unavailable.