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tcp_connections

tcp_connections

OS: Linux

This alert presents the percentage of used IPv4 TCP connections. If you receive it, it is an indication of high IPv4 TCP connections utilization.

If this value is 100% then the system is no longer able to establish new TCP connections.

  • This alert is raised to a state of warning when the percentage of used IPv4 TCP connections is
    greater than 80% and less than 90%.
  • If the percentage of used IPv4 TCP connections exceeds 90%, then the alert gets raised to critical.
TCP Connections Alarm Settings

Inside the tcp_conn.conf, on the calc: line, there is this block of code:
(${tcp_max_connections} > 0) ? ( ${connections} * 100 / ${tcp_max_connections} ) : 0

  • That line of code will calculate the value of $this in the following lines.
  • Essentially, if the max connections are not dynamic, and there is a limit, then we calculate the
    percentage of used IPv4 TCP connections. Otherwise, we have a dynamic threshold
    (so ${tcp_max_connections} may be nan or -1), which in this case the alert and $this will
    always be zero.