Part of the Mozilla Bouncer project, Sentry 2 is a program that monitors the mirrors from which people can download Mozilla products. It can perform several types of integrity tests from cursory to thorough. It can be configured through environment variables, a configuration file or command line options. It can run in a one time ad hoc mode or scheduled using cron.

The program is written as a multithreaded Python 2.3 application using a few external open-source modules.

Sentry 2 can perform five different types of test on the mirrors:

• full test - every file on every mirror is downloaded. It checks the MIME type of the download to make sure it is the expected type. It also calculates an MD5 or SHA1 checksum to test file integrity.
• new mirror/file test - this tests all files on new mirrors and/or all new files on all mirrors. It performs the same tests as the full test.
• file test - every file on every mirror is touched. It only checks to make sure the MIME type is correct.
• mirror test - it touches one random file on each mirror just to see if the mirror is responding in reasonable time
• random full test - pick one random file from each mirror and do a full download and hash test