monit

About monit

From Debian's package description

monit is a utility for monitoring and managing daemons or similar programs running on a Unix system. It will start specified programs if they are not running and restart programs not responding.

monit supports:

• Daemon mode - poll programs at a specified interval
• Monitoring modes - active, passive or manual
• Start, stop and restart of programs
• Group and manage groups of programs
• Process dependency definition
• Logging to syslog or own logfile
• Configuration - comprehensive controlfile
• Runtime and TCP/IP port checking (tcp and udp)
• SSL support for port checking
• Unix domain socket checking
• Process status and process timeout
• Process cpu usage
• Process memory usage
• Process zombie check
• Check the systems load average
• Check a file or directory timestamp
• Alert, stop or restart a process based on its characteristics
• MD5 checksum for programs started and stopped by monit
• Alert notification for program timeout, restart, checksum, stop resource and timestamp error
• Flexible and customizable email alert messages
• Protocol verification. HTTP, FTP, SMTP, POP, IMAP, NNTP, SSH, DWP, LDAPv2 and LDAPv3
• An http interface with optional SSL support to make monit accessible from a webbrowser

From Debian's description of the monit package, under that package's license.