Collectors

This page contains information about all Collectors included with MOM including the data collected and configuration information. The most up to date information on Collector fields will always be in the source code itself but this page will be kept as up to date as possible.

When writing MOM policies, use the data fields described here to access host and guest statistics. The fields may only be accessed in a policy if the corresponding Collector is loaded. When two Collectors provide the same field, the Collector listed first in the mom configuration file will supersede the others.

Host statistics are accessed using the following syntax:

Host.<field>	Access the latest value for <field>
(Host.StatAvg "<field>")	Access the moving average of <field>

Guest statistics are accessed in a similar fashion using the iterator given by the with construct (see Policy for details):

(with Guests guest {
    (defvar foo guest.<field>)
    (defvar bar (guest.StatAvg "<field>"))
})

HostMemory

This collector gathers general memory statistics about the host.
Setup: To use this Collector, simply enable it in the mom configuration file

For example:

[host]
collectors: HostMemory

Data: This Collector provides the following host data

mem_available	The total amount of available memory (kB)
mem_unused	The amount of memory that is not being used for any purpose (kB)
mem_free	The amount of free memory including some caches (kB)
swap_in	The amount of memory swapped in since the last collection (pages)
swap_out	The amount of memory swapped out since the last collection (pages)
anon_pages	The amount of memory used for anonymous memory areas (kB)

HostKSM

This collector exposes host KSM statistics as reported in sysfs.

Setup: Enable in the mom config file. If your host does not support KSM this Collector will raise a Fatal Error.

[host]
collectors: HostMemory, HostKSM

Data: This Collector provides the following host data

ksm_run	Status of the KSM daemon: 0 – Stopped, 1 – Running
ksm_sleep_millisecs	The amount of idle time between scans (ms)
ksm_pages_shared	The number of pages being shared
ksm_pages_sharing	The number of sites where a shared page is in use
ksm_pages_unshared	The number of pages that are scanned but not shared
ksm_pages_to_scan	The number of pages to scan in each work interval
ksm_pages_volatile	The number of pages that are changing too fast to be shared
ksm_full_scans	The number of times all mergeable memory areas have been scanned
ksm_shareable	Estimated amount of host memory that is eligible for sharing

GuestLibvirt

A collector that uses libvirt to gather information about running guests.

Setup: Enable in the mom configuration file

[guest]
collectors: GuestLibvirt

Data: This Collector always provides the following guest data

libvirt_state	The domain state defined by libvirt as:
	VIR_DOMAIN_NOSTATE = 0 : no state
	VIR_DOMAIN_RUNNING = 1 : the domain is running
	VIR_DOMAIN_BLOCKED = 2 : the domain is blocked on resource
	VIR_DOMAIN_PAUSED = 3 : the domain is paused by user
	VIR_DOMAIN_SHUTDOWN = 4 : the domain is being shut down
	VIR_DOMAIN_SHUTOFF = 5 : the domain is shut off
	VIR_DOMAIN_CRASHED = 6 : the domain is crashed
libvirt_maxmem	The maximum amount of memory the guest may use
libvirt_curmem	The current memory limit (set by ballooning)

If libvirt memory statistics are enabled on the host and guest then the following guest statistics are provided:

mem_available	Total amount of memory available (kB)
mem_unused	Amount of free memory not including caches (kB)
major_fault	Total number of major page faults
minor_fault	Total number of minor page faults
swap_in	Total amount of memory swapped in (kB)
swap_out	Total amount of memory swapped out (kB)

GuestQemuProc

This Collector returns statistics for the qemu process representing a guest.

Setup: Enable in the mom configuration file

[guest]
collectors: GuestLibvirt, GuestQemuProc

Data: This Collector provides the following guest data

host_minor_faults	The number of host minor faults a guest’s qemu process caused since the last collection.
host_major_faults	The number of host major faults a guest’s qemu process caused since the last collection.
rss	The resident set size counts the number of resident pages associated with this qemu process.

NOTE: Host major faults generally require host disk IO to satisfy, host minor faults do not.

GuestNetworkDaemon

This collector communicates over the network with a program running on the guest to gather guest memory statistics.

Setup: Since this Collector depends on a server program in the guest and a network connection to this server, the setup for this Collector is more involved. In short, you need to set up the following to use this Collector:

• Guest name to guest IP address mapping
• The MOM guest daemon (mom-guestd) must be running in the guest

There is no standardized way to determine a guest’s IP address since network setup is site-specific. In order to connect to guests, MOM relies on a helper program to map libvirt guest names to IP addresses. You must customize a name-to-ip program (see the example in the documentation) to fit your environment and set the path to that program in the mom configuration file. Here is an example:

Sample name-to-ip script

#!/bin/bash
# name-to-ip: Map a guest name to an IP address
#
# There is no standard method of determining the IP address of a given guest.
# Therefore, MOM makes use of a helper program that can be customized according
# to the host network configuration.
#
# This script will be called with the domain name (as returned by the
# virDomainGetName() libvirt API).  The output should be an IPv4 IP address
# only.  On error, return nothing.

NAME=$1

# Example 1: The name is the IP address
# echo -n $NAME

# Example 2: The name is a valid hostname
# nslookup $NAME | grep '^Server' | awk '{print $2}'

# Example 3: The name contains a sequence number which maps directly to a range
# of local IP addresses
NUM=${NAME##*-}
IP="192.168.123.$[ $NUM + 1 ]"
echo $IP

MOM configuration file entry

[guest]
...
name-to-ip-helper: /usr/local/bin/name-to-ip

Data: This Collector provides the following guest data

mem_available	The total amount of available memory (kB)
mem_unused	The amount of memory that is not being used for any purpose (kB)
major_fault	Total number of major page faults
minor_fault	Total number of minor page faults
swap_in	The amount of memory swapped in since the last collection (pages)
swap_out	The amount of memory swapped out since the last collection (pages)