banshee/linux-collection/linux/snmp/swap

Swap of a Linux host, by SNMP

Returns the size of the swap, the swap used and free, and the share used. Two watches are offered, each adjustable on the probe.

Versions

Generic: the memory group of UCD-SNMP-MIB is served the same way by net-snmp on any Linux.

How it works

The collector reads memTotalSwap and memAvailSwap (the free swap), in KiB, from the memory group of UCD-SNMP-MIB.

A machine without swap says so by a size of zero: the collector returns zero everywhere, a measurement and not a failure, and no watch raises.

Prerequisites

snmpd (net-snmp) running on the host, listening on an address the poller reaches (UDP 161), with the firewall open to the poller only.
The view granted to the poller includes the memory group of UCD-SNMP-MIB (.1.3.6.1.4.1.2021.4).
Read-only access, SNMPv2c or SNMPv3, set on the host or one of its folders (protocol:snmp:* variables).

# /etc/snmp/snmpd.conf
agentaddress udp:161
view   banshee included .1.3.6.1.4.1.2021.4
rocommunity <community> 192.0.2.10 -V banshee
# or: rouser <user> priv -V banshee

Outputs

Name	Label	Unit	Per instance
`total`	Swap size	MiB	no
`used`	Used swap	MiB	no
`free`	Free swap	MiB	no
`used-percent`	Used swap	%	no

Watches

Name	Title	Kind	Defaults	Checked by default
`swap-high`	Swap saturated	above a threshold, on `used-percent`	warning above 80 %, critical above 95 %, for 3 runs	yes
`free`	Little free swap	below a threshold, on `free`	critical below 512 MiB; no warning	no

Limits

Swap in use is not swapping activity: a machine can hold idle pages in swap for weeks without harm. The rate of pages swapped in and out is not served by this MIB.
These values are 31 bits wide in KiB: beyond 2 TiB of swap, the agent itself miscounts them.