• Mike Hibler's avatar
    Introduce sitevars to control the sensitivity of alerts. · 2962b32f
    Mike Hibler authored
    The sitevars are a bit obscure:
    
      # cnetwatch/check_interval
      #   Interval at which to collect info.
      #   Zero means don't run cnetwatch (exit immediately).
      #
      # cnetwatch/alert_interval
      #   Interval over which to calculate packet/bit rates and to log alerts.
      #   Should be an integer multiple of the check_interval.
      #
      # cnetwatch/pps_threshold
      #   Packet rate (packets/sec) in excess of which to log an alert.
      #   Zero means don't generate packet rate alerts.
      #
      # cnetwatch/bps_threshold
      #   Data rate (bits/sec) in excess of which to log an alert.
      #   Zero means don't generate data rate alerts.
      #
      # cnetwatch/mail_interval
      #   Interval at which to send email for all alerts logged during the interval.
      #   Zero means don't ever send email.
      #
      # cnetwatch/mail_max
      #   Maximum number of alert emails to send; after this alerts are only logged.
      #   Zero means no limit to the emails.
    
    Basically you can tweak pps_threshold and bps_threshold to define what you
    think an unusual "burst" of cnet traffic is and then alert_interval to
    determine how long a burst has to last before you will send an alert.
    
    Why would you have check_interval less than alert_interval? You probably
    wouldn't unless you want to record finer-grained port stats using the -l
    option to write stats to a logfile. We do it on the mothership as a data
    source for some student machine learning projects. Note that in an environment
    with lots of control net switches, a single instance of gathering port
    counters from the switches could take 30 seconds or longer (on the mothership
    it can take minutes). So don't set check_interval too low.
    
    The mail_* variables are paranoia about sending too much email due to runaway
    nodes. The mail_interval just coalesces alerts to reduce messages, and
    mail_max is the maximum number of emails that one instance of cnetwatch will
    send. The latter is a pretty silly mechanism as a long running cnetwatch will
    probably hit the limit legitiamtely after 6 months or so and you will have to
    restart it.
    2962b32f
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