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mon(8) Parallel Service Monitoring Daemon mon(8)
NAME
mon - monitor services for availability, sending alarms upon failures.
SYNOPSIS
mon [-dfhlMSv] [-a dir] [-A authfile] [-b dir] [-B dir] [-c config] [-D
dir] [-i secs] [-k num] [-l [statetype]] [-L dir] [-m num] [-p num] [-P
pidfile] [-r delay] [-s dir]
DESCRIPTION
mon is a general-purpose scheduler for monitoring service availability
and triggering alerts upon detecting failures. mon was designed to be
open in the sense that it supports arbitrary monitoring facilities and
alert methods via a common interface, which are easily implemented
through programs (in C, Perl, shell, etc.), SNMP traps, and special Mon
(UDP packet) traps.
OPTIONS
-a dir Path to alert scripts. Default is
/usr/local/lib/mon/alert.d:alert.d. Multiple alert paths may be
specified by separating them with a colon. Non-absolute paths
are taken to be relative to the base directory (/usr/lib/mon by
default).
-b dir Base directory for mon. scriptdir, alertdir, and statedir are
all relative to this directory unless specified from /. Default
is /usr/lib/mon.
-B dir Configuration file base directory. All config files are located
here, including mon.cf, monusers.cf, and auth.cf.
-A authfile
Authentication configuration file. By default this is
/etc/mon/auth.cf if the /etc/mon directory exists, or
/usr/lib/mon/auth.cf otherwise.
-c file
Read configuration from file. This defaults to IR
/etc/mon/mon.cf " if the " /etc/mon directory exists, otherwise
to /etc/mon.cf.
-d Enable debugging mode.
-D dir Path to state directory. Default is the first of
/var/state/mon, /var/lib/mon, and /usr/lib/mon/state.d which
exists.
-f Fork and run as a daemon process. This is the preferred way to
run mon.
-h Print help information.
-i secs
Sleep interval, in seconds. Defaults to 1. This shouldnât need
to be adjusted for any reason.
-k num Set log history to a maximum of num entries. Defaults to 100.
-l statetype
Load state from the last saved state file. The supported saved
state types are disabled for disabled watches, services, and
hosts, opstatus for failure/alert/ack status of all services,
and all for both. If no statetype is provided, disabled is
assumed.
-L dir Sets the log dir. See also logdir in the configuration file.
The default is /var/log/mon if that directory exists, otherwise
log.d in the base directory.
-M Pre-process the configuration file with the macro expansion
package m4.
-m num Set the throttle for the maximum number of processes to num.
-p num Make server listen on port num. This defaults to 2583.
-S Start with the scheduler stopped.
-P pidfile
Store the serverâs pid in pidfile, the default is the first of
/var/run/mon/mon.pid, /var/run/mon.pid, and /etc/mon.pid whose
directory exists. An empty value tells mon not to use a pid
file.
-r delay
Sets the number of seconds used to randomize the startup delay
before each service is scheduled. Refer to the global randstart
variable in the configuration file.
-s dir Path to monitor scripts. Default is
/usr/local/lib/mon/mon.d:mon.d. Multiple alert paths may be
specified by separating them with a colon. Non-absolute paths
are taken to be relative to the base directory (/usr/lib/mon by
default).
-v Print version information.
DEFINITIONS
monitor
A program which tests for a certain condition, returns either
true or false, and optionally produces output to be passed back
to the scheduler. Common monitors detect host reachability via
ICMP echo messages, or connection to TCP services.
period A period in time as interpreted by the Time::Period module.
alert A program which sends a message when invoked by the scheduler.
The scheduler calls upon an alert when it detects a failure from
a monitor. An alert program accepts a set of command-line argu-
ments from the scheduler, in addition to data via standard
input.
hostgroup
A single host or list of hosts, specified as names or IP
addresses.
service
A collection of parameters used to deal with monitoring a par-
ticular resource which is provided by a group. Services are usu-
ally modeled after things such as an SMTP server, ICMP echo
capability, server disk space availability, or SNMP events.
view A collection of hostgroups, used to filter mon output for client
display. i.e. a ânetwork-servicesâ view might be defined so
your network staff can see just the hostgroups which matter to
them, without having to see all hostgroups defined in Mon.
watch A collection of services which apply to a particular group.
OPERATION
When the mon scheduler starts, it reads a configuration file to deter-
mine the services it needs to monitor. The configuration file defaults
to /etc/mon.cf, and can be specified using the -c parameter. If the -M
option is specified, then the configuration file is pre-processed with
m4. If the configuration file ends with .m4, the file is also pro-
cessed by m4 automatically.
The scheduler enters a loop which handles client connections, monitor
invocations, and failure alerts. Each service has a timer, specified in
the configuration file as the interval variable, which tells the sched-
uler how frequently to invoke a monitor process. The scheduler may be
temporarily stopped. While it is stopped, client access still func-
tions, but it just doesnât schedule things. This is useful in conjunc-
tion while resetting the server, because you can do this: save the
hosts and services which are disabled, reset the server with the sched-
uler stopped, re-disabled those hosts and services, then start the
scheduler. It also allows making atomic changes across several client
connections. See the moncmd man page for more information.
MONITOR PROGRAMS
Monitor processes are invoked with the arguments specified in the con-
figuration file, appended by the hosts from the applicable host group.
For example, if the watch group is "servers", which contain the host-
names "smtp", "nntp", and "ns", and the monitor line reads as follows,
monitor fping.monitor -t 4000 -r 2
then the exectuable "fping.monitor" will be executed with these parame-
ters:
MONITOR_DIR/fping.monitor -t 4000 -r 2 smtp nntp ns
MONITOR_DIR is actually a search path, by default
/usr/local/lib/mon/mon.d then /usr/lib/mon/mon.d, but it can be over-
ridden by the -s option or in the configuration file. If all hosts in
the hostgroup have been disabled, then a warning is sent to syslog and
the monitor is not run. This behavior may be overridden with the
"allow_empty_group" option in the service definition. If the final
argument to the "monitor" line is ";;" (it must be preceded by whites-
pace), then the host list will not be appended to the parameter list.
In addition to environment variables defined by the user in the service
definition, mon passes certain variables to monitor process.
MON_LAST_SUMMARY
The first line of the output from the last time the monitor
exited. This is not the summary of the current monitor run, but
the previous one. This may be used by an alert script to pro-
vide historical context in an alert.
MON_LAST_OUTPUT
The entire output of the monitor from the last time it exited.
This is not the output of the current monitor run, but the pre-
vious one. This may be used by an alert script to provide his-
torical context in an alert.
MON_LAST_FAILURE
The time(2) of the last failure for this service.
MON_FIRST_FAILURE
The time(2) of the first time this service failed.
MON_LAST_SUCCESS
The time(2) of the last time this service passed.
MON_DESCRIPTION
The description of this service, as defined in the configuration
file using the description tag.
MON_DEPEND_STATUS
The depend status, "o" if dependency failure, "1" otherwise.
MON_LOGDIR
The directory log files should be placed, as indicated by the
logdir global configuration variable.
MON_STATEDIR
The directory where state files should be kept, as indicated by
the statedir global configuration variable.
MON_CFBASEDIR
The directory where configuration files should be kept, as indi-
cated by the cfbasedir global configuration variable.
"fping.monitor" should return an exit status of 0 if it completed suc-
cessfully (found no problems), or nonzero if a problem was detected.
The first line of output from the monitor script has a special meaning:
it is used as a brief summary of the exact failure which was detected,
and is passed to the alert program. All remaining output is also passed
to the alert program, but it has no required interpretation.
If a monitor for a particular service is still running, and the time
comes for mon to run another monitor for that service, it will not
start another monitor. For example, if the interval is 10s, and the
monitor does not finish running within 10 seconds, then mon will wait
until the first monitor exits before running another one.
ALERT DECISION LOGIC
Upon a non-zero or zero exit status, the associated alert or upalert
program (respectively) is started, pending the following conditions: If
an alert for a specific service is disabled, do not send an alert. If
dep_behavior is set to âaâ, or alertdepend is set, and a parent depen-
dency is failing, then suppress the alert. If the alert has previously
been acknowledged, do not send the alert, unless it is an upalert. If
an alert is not within the specified period, record the failure via
syslog(3) and do not send an alert. If the failure does not fall
within a defined period, do not send an alert. No upalerts are sent
without corresponding down alerts, unless no_comp_alerts is defined in
the period section. An upalert will only be sent if the previous state
is a failure. If an alert was already sent within the last alertevery
interval, do not send another alert, unless the summary output from the
current monitor program differs from the last monitor process. Other-
wise, send an alert using each alert program listed for that period.
The observe_detail argument to alertevery affects this behavior by
observing the changes in the detail part of the output in addition to
the summary line. If a monitor has successive failures and the summary
output changes in each of them, alertevery will not suppress multiple
consecutive alerts. The reasoning is that if the summary output
changes, then a significant event occurred and the user should be
alerted. The "strict" argument to alertevery will suppress both com-
paring the output from the previous monitor run to the current and pre-
vent a successful return value of the monitor from resetting the
alertevery timer. For example, "alertevery 24h strict" will only send
out an alert once every 24 hours, regardless of whether the monitor
output changes, or if the service stops and then starts failing.
ALERT PROGRAMS
Alert programs are found in the path supplied with the -a parameter, or
in the /usr/local/lib/mon/alert.d and directories if not specified.
They are invoked with the following command-line parameters:
-s service
Service tag from the configuration file.
-g group
Host group name from the configuration file.
-h hosts
The expanded version of the host group, space delimited, but
contained in one shell "word".
-l alertevery
The number of seconds until the next alarm will be sent.
-O This option is supplied to an alert only if the alert is
being generated as a result of an expected traap timing out
-t time
The time (in time(2) format) of when this failure condition was
detected.
-T This option is supplied to an alert only if the alert was trig-
gered by a trap
-u This option is supplied to an alert only if it is being called
as an upalert.
The remaining arguments are supplied from the trailing parameters in
the configuration file, after the "alert" service parameter.
As with monitor programs, alert programs are invoked with environment
variables defined by the user in the service definition, in addition to
the following which are explicitly set by the server:
MON_LAST_SUMMARY
The first line of the output from the last time the monitor
exited.
MON_LAST_OUTPUT
The entire output of the monitor from the last time it exited.
MON_LAST_FAILURE
The time(2) of the last failure for this service.
MON_FIRST_FAILURE
The time(2) of the first time this service failed.
MON_LAST_SUCCESS
The time(2) of the last time this service passed.
MON_DESCRIPTION
The description of this service, as defined in the configuration
file using the description tag.
MON_GROUP
The watch group which triggered this alarm
MON_SERVICE
The service heading which generated this alert
MON_RETVAL
The exit value of the failed monitor program, or return value as
accepted from a trap.
MON_OPSTATUS
The operational status of the service.
MON_ALERTTYPE
Has one of the following values: "failure", "up", "startup",
"trap", or "traptimeout", and signifies the type of alert which
was triggered.
MON_TRAP_INTENDED
This is only set when an unknown mon trap is received and caught
by the default/defaut watch/service. This contains colon sepa-
rated entries of the trapâs intended watch group and service
name.
MON_LOGDIR
The directory log files should be placed, as indicated by the
logdir global configuration variable.
MON_STATEDIR
The directory where state files should be kept, as indicated by
the statedir global configuration variable.
MON_CFBASEDIR
The directory where configuration files should be kept, as indi-
cated by the cfbasedir global configuration variable.
The first line from standard input must be used as a brief summary of
the problem, normally supplied as the subject line of an email, or text
sent to an alphanumeric pager. Interpretation of all subsequent lines
read from stdin is left up to the alerting program. The usual parame-
ters are a list of recipients to deliver the notification to. The
interpretation of the recipients is not specified, and is up to the
alert program.
CONFIGURATION FILE
The configuration file consists of zero or more hostgroup definitions,
and one or more watch definitions. Each watch definition may have one
or more service definitions. A line beginning with optional leading
whitespace and a pound ("#") is regarded as a comment, and is ignored.
Lines are parsed as they are read. Long lines may be continued by end-
ing them with a backslash ("\"). If a line is continued, then the
backslash, the trailing whitespace after the backslash, and the leading
whitespace of the following line are removed. The end result is assem-
bled into a single line.
Global Variables
The following variables may be set to override compiled-in defaults.
Command-line options will have a higher precedence than these defini-
tions.
alertdir = dir
dir is the full path to the alert scripts. This is the value set
by the -a command-line parameter.
Multiple alert paths may be specified by separating them with a
colon. Non-absolute paths are taken to be relative to the base
directory (/usr/lib/mon by default).
When the configuration file is read, all alerts referenced from
the configuration will be looked up in each of these paths, and
the full path to the first instance of the alert found is stored
in a hash. This hash is only generated upon startup or after a
"reset" command, so newly added alert scripts will not be recog-
nized until a "reset" is performed.
mondir = dir
dir is the full path to the monitor scripts. This value may also
be set by the -s command-line parameter. If this path does not
begin with a "/", it will be relative to basedir.
Multiple alert paths may be specified by separating them with a
colon. All paths must be absolute.
When the configuration file is read, all monitors referenced
from the configuration will be looked up in each of these paths,
and the full path to the first instance of the monitor found is
stored in a hash. This hash is only generated upon startup or
after a "reset" command, so newly added monitor scripts will not
be recognized until a "reset" is performed.
statedir = dir
dir is the full path to the state directory. mon uses this
directory to save various state information. If this path does
not begin with a "/", it will be relative to basedir.
logdir = dir
dir is the full path to the log directory. mon uses this direc-
tory to save various logs, including the downtime log. If this
path does not begin with a "/", it will be relative to basedir.
basedir = dir
dir is the full path for the state, log, monitor, and alert
directories.
cfbasedir = dir
dir is the full path where all the config files can be found
(monusers.cf, auth.cf, etc.).
authfile = file
file is the path to the authentication file. If the path does
not begin with a "/", it will be relative to cfbasedir.
authtype = type [type...]
type is the type of authentication to use. A space-separated
list of types may be specified, and they will be checked the
order they are listed. As soon as a successful authentication is
performed, the user is considered authenticated by mon for the
duration of the session and no more authentication checks are
performed.
If type is getpwnam, then the standard Unix passwd file authen-
tication method will be used (calls getpwnam(3) on the user and
compares the crypt(3)ed version of the password with what it
gets from getpwnam). This will not work if shadow passwords are
enabled on the system.
If type is userfile, then usernames and hashed passwords are
read from userfile, which is defined via the userfile configura-
tion variable.
If type is pam, then PAM (pluggable authentication modules) will
be used for authentication. The service specified by the pam-
service global will be used. If no global is given, the PAM
passwd service will be used.
If type is trustlocal, then if the client connection comes from
locahost, the username passed from the client will be trusted,
and the password will be ignored. This can be used when you
want the client to handle the authentication for you. I.e. a
CGI script using one of the many apache authentication methods.
userfile = file
This file is used when authtype is set to userfile. It consists
of a sequence of lines of the format âusername : passwordâ.
password is stored as the hash returned by the standard Unix
crypt(3) function. NOTE: the format of this file is compatible
with the Apache file based username/password file format. It is
possible to use the htpasswd program supplied with Apache to
manage the mon userfile.
Blank lines and lines beginning with # are ignored.
pamservice = service
The PAM service used for authentication. This is applicable only
if "pam" is specified as a parameter to the authtype setting. If
this global is not defined, it defaults to passwd.
serverbind = addr
trapbind = addr
serverbind and trapbind specify which address to bind the server
and trap ports to, respectively. If these are not defined, the
default address is INADDR_ANY, which allows connections on all
interfaces. For security reasons, it could be a good idea to
bind only to the loopback interface.
dtlogfile = file
file is a file which will be used to record the downtime log.
Whenever a service fails for some amount of time and then stop
failing, this event is written to the log. If this parameter is
not set, no logging is done. The format of the file is as fol-
lows (# is a comment and may be ignored):
timenoticed group service firstfail downtime interval summary.
timenoticed is the time(2) the service came back up.
group service is the group and service which failed.
firstfail is the time(2) when the service began to fail.
downtime is the number of seconds the service failed.
interval is the frequency (in seconds) that the service is
polled.
summary is the summary line from when the service was failing.
monerrfile = filename
By default, when mon daemonizes itself, it connects stdout and
stderr to /dev/null. If monerrfile is set to a file, then stdout
and stderr will be appended to that file. In all cases stdin is
connected to /dev/null. If mon is told to run in the foreground
and to not daemonize, then none of this applies, since
stdin/stdout/stderr stay connected to whatever they were at the
time of invocation.
dtlogging = yes/no
Turns downtime logging on or off. The default is off.
histlength = num
num is the the maximum number of events to be retained in his-
tory list. The default is 100. This value may also be set by
the -k command-line parameter.
historicfile = file
If this variable is set, then alerts are logged to file, and
upon startup, some (or all) of the past history is read into
memory.
historictime = timeval
num is the amount of the history file to read upon startup.
"Now" - timeval is read. See the explanation of interval in the
"Service Definitions" section for a description of timeval.
serverport = port
port is the TCP port number that the server should bind to. This
value may also be set by the -p command-line parameter. Normally
this port is looked up via getservbyname(3), and it defaults to
2583.
trapport = port
port is the UDP port number that the trap server should bind to.
Normally this port is looked up via getservbyname(3), and it
defaults to 2583.
pidfile = path
path is the file the sever will store its pid in. This value
may also be set by the -P command-line parameter.
maxprocs = num
Throttles the number of concurrently forked processes to num.
The intent is to provide a safety net for the unlikely situation
when the server tries to take on too many tasks at once. Note
that this situation has only been reported to happen when trying
to use a garbled configuration file! You donât want to use a
garbled configuration file now, do you?
cltimeout = secs
Sets the client inactivity timeout to secs. This is meant to
help thwart denial of service attacks or recover from crashed
clients. secs is interpreted as a "1h/1m/1s" string, where "1m"
= 60 seconds.
randstart = interval
When the server starts, normally all services will not be sched-
uled until the interval defined in the respective service sec-
tion. This can cause long delays before the first check of a
service, and possibly a high load on the server if multiple
things are scheduled at the same intervals. This option is used
to randomize the scheduling of the first test for all services
during the startup period, and immediately after the reset com-
mand. If randstart is defined, the scheduled run time of all
services of all watch groups will be a random number between
zero and randstart seconds.
dep_recur_limit = depth
Limit dependency recursion level to depth. If dependency recur-
sion (dependencies which depend on other dependencies) tries to
go beyond depth, then the recursion is aborted and a messages is
logged to syslog. The default limit is 10.
dep_behavior = {a|m|hm}
dep_behavior controls whether the dependency expression sup-
presses one of: the running of alerts, the running of monitors,
or the passing of individual hosts to the monitors. Read more
about the behavior in the "Service Definitions" section below.
This is a global setting which controls the default settings for
the service-specified variable.
dep_memory = timeval
If set, dep_memory will cause dependencies to continue to pre-
vent alerts/monitoring for a period of time after the service
returns to a normal state. This can be used to prevent over-
eager alerting when a machine is rebooting, for example. See
the explanation of interval in the "Service Definitions" section
for a description of timeval.
This is a global setting which controls the default settings for
the service-specified variable.
syslog_facility = facility
Specifies the syslog facility used for logging. daemon is the
default.
startupalerts_on_reset = {yes|no}
If set to "yes", startupalerts will be invoked when the reset
client command is executed. The default is "no".
monremote = program
If set, this external program will be called by Mon when various
client requests are processed. This can be used to propagate
those changes from one Mon server to another, if you have multi-
ple monitoring machines. An example script, monremote.pl is
available in the clients directory.
Hostgroup Entries
Hostgroup entries begin with the keyword hostgroup, and are followed by
a hostgroup tag and one or more hostnames or IP addresses, separated by
whitespace. The hostgroup tag must be composed of alphanumeric charac-
ters, a dash ("-"), a period ("."), or an underscore ("_"). Non-blank
lines following the first hostgroup line are interpreted as more host-
names. The hostgroup definition ends with a blank line. For example:
hostgroup servers nameserver smtpserver nntpserver
nfsserver httpserver smbserver
hostgroup router_group cisco7000 agsplus
View Entries
View entries begin with the keyword view, and are followed by a view
tag and the names of one or more hostgroups. The view tag must be com-
posed of alphanumeric characters, a dash ("-"), a period ("."), or an
underscore ("_"). Non-blank lines following the first view line are
interpreted as more hostgroup names. The view definition ends with a
blank line. For example:
view servers dns-servers web-servers file-servers
mail-servers
view network-services routers switches vpn-servers
Watch Group Entries
Watch entries begin with a line that starts with the keyword watch,
followed by whitespace and a single word which normally refers to a
pre-defined hostgroup. If the second word is not recognized as a host-
group tag, a new hostgroup is created whose tag is that word, and that
word is its only member.
Watch entries consist of one or more service definitions.
There is a special watch group entry called "default". If a default
watch group is defined with a "default" service entry, then this defi-
nition will be used in handling unknown mon traps.
Service Definitions
service servicename
A service definition begins with they keyword service followed
by a word which is the tag for this service. This word must be
unique among all services defined for the same watch group.
The components of a service are an interval, monitor, and one or
more time period definitions, as defined below.
If a service name of "default" is defined within a watch group
called "dafault" (see above), then the default/default defini-
tion will be used for handling unknown mon traps.
The following configuration parameters are valid only following
a service definition:
VARIABLE=value
Environment variables may be defined for each service, which
will be included in the environment of monitors and alerts.
Variables must be specified in all capital letters, must begin
with an alphabetical character or an underscore, and there must
be no spaces to the left of the equal sign.
interval timeval
The keyword interval followed by a time value specifies the fre-
quency that a monitor script will be triggered. Time values are
defined as "30s", "5m", "1h", or "1d", meaning 30 seconds, 5
minutes, 1 hour, or 1 day. The numeric portion may be a frac-
tion, such as "1.5h" or an hour and a half. This format of a
time specification will be referred to as timeval.
failure_interval timeval
Adjusts the polling interval to timeval when the service check
is failing. Resets the interval to the original when the service
succeeds.
traptimeout timeval
This keyword takes the same time specification argument as
interval, and makes the service expect a trap from an external
source at least that often, else a failure will be registered.
This is used for a heartbeat-style service.
trapduration timeval
If a trap is received, the status of the service the trap was
delivered to will normally remain constant. If trapduration is
specified, the status of the service will remain in a failure
state for the duration specified by timeval, and then it will be
reset to "success".
randskew timeval
Rather than schedule the monitor script to run at the start of
each interval, randomly adjust the interval specified by the
interval parameter by plus-or-minus randskew . The skew value
is specified as the interval parameter: "30s", "5m", etc... For
example if interval is 1m, and randskew is "5s", then mon will
schedule the monitor script some time between every 55 seconds
and 65 seconds. The intent is to help distribute the load on
the server when many services are scheduled at the same inter-
vals.
monitor monitor-name [arg...]
The keyword monitor followed by a script name and arguments
specifies the monitor to run when the timer expires. Shell-like
quoting conventions are followed when specifying the arguments
to send to the monitor script. The script is invoked from the
directory given with the -s argument, and all following words
are supplied as arguments to the monitor program, followed by
the list of hosts in the group referred to by the current watch
group. If the monitor line ends with ";;" as a separate word,
the host groups are not appended to the argument list when the
program is invoked.
allow_empty_group
The allow_empty_group option will allow a monitor to be invoked
even when the hostgroup for that watch is empty because of dis-
abled hosts. The default behavior is not to invoke the monitor
when all hosts in a hostgroup have been disabled.
description descriptiontext
The text following description is queried by client programs,
passed to alerts and monitors via an environment variable. It
should contain a brief description of the service, suitable for
inclusion in an email or on a web page.
exclude_hosts host [host...]
Any hosts listed after exclude_hosts will be excluded from the
service check.
exclude_period periodspec
Do not run a scheduled monitor during the time identified by
periodspec.
depend dependexpression
The depend keyword is used to specify a dependency expression,
which evaluates to either true of false, in the boolean sense.
Dependencies are actual Perl expressions, and must obey all syn-
tactical rules. The expressions are evaluated in their own pack-
age space so as to not accidentally have some unwanted side-
effect. If a syntax error is found when evaluating the expres-
sion, it is logged via syslog.
Before evaluation, the following substitutions on the expression
occur: phrases which look like "group:service" are substituted
with the value of the current operational status of that speci-
fied service. These opstatus substitutions are computed recur-
sively, so if service A depends upon service B, and service B
depends upon service C, then service A depends upon service C.
Successful operational statuses (which evaluate to "1") are
"STAT_OK", "STAT_COLDSTART", "STAT_WARMSTART", and
"STAT_UNKNOWN". The word "SELF" (in all caps) can be used for
the group (e.g. "SELF:service"), and is an abbreviation for the
current watch group.
This feature can be used to control alerts for services which
are dependent on other services, e.g. an SMTP test which is
dependent upon the machine being ping-reachable.
dep_behavior {a|m|hm}
The evaluation of the dependency graphs specified via the depend
keyword can control the suppression of alert or monitor invoca-
tions, or the suppression of individual hosts passed to the mon-
itor.
Alert suppression. If this option is set to "a", then the
dependency expression will be evaluated after the monitor for
the service exits or after a trap is received. An alert will
only be sent if the evaluation succeeds, meaning that none of
the nodes in the dependency graph indicate failure.
Monitor suppression. If it is set to "m", then the dependency
expression will be evaulated before the monitor for the service
is about to run. If the evaulation succeeds, then the monitor
will be run. Otherwise, the monitor will not be run and the sta-
tus of the service will remain the same.
Host suppression. If it is set to "hm" then Mon will extract
the list of "parent" services from the dependency expression.
(In fact the expression can be just a list of services.) Then
when the monitor for the service is about to be run, for each
host in the current hostgroup Mon will search all the parent
services which are currently failing and look for the hostname
in the current summary output. If the hostname is found, this
host will be excluded from this run of the monitor. This can be
used to e.g. allow an SMTP test on a group of hosts to still be
run even when a single host is not ping-reachable. If all the
rest of the hosts are working fine, the service will be in an OK
state, but if another host fails the SMTP test Mon can still
alert about that host even though the parent dependency was
failing. The dependency expression will not be used recursively
in this case.
alertdepend dependexpression
monitordepend dependexpression
hostdepend dependexpression
These keywords allow you to specify multiple dependency expres-
sions of different types. Each one corresponds to the different
dep_behavior settings listed above. They will be evaluated
independently in the different contexts as listed above. If
depend is present, it takes precedence over the matching key-
word, depending on the dep_behavior setting.
dep_memory timeval
If set, dep_memory will cause dependencies to continue to pre-
vent alerts/monitoring for a period of time after the service
returns to a normal state. This can be used to prevent over-
eager alerting when a machine is rebooting, for example. See
the explanation of interval in the "Service Definitions" section
for a description of timeval.
redistribute alert [arg...]
A service may have one redistribute option, which is a special
form of an an alert definition. This alert will be called on
every service status update, even sequential success status
updates. This can be used to integrate Mon with another moni-
toring system, or to link together multiple Mon servers via an
alert script that generates Mon traps. See the "ALERT PROGRAMS"
section above for a list of the parameters mon will pass auto-
matically to alert programs.
unack_summary
Remove the "acknowledged" state from a service if the summary
component of the failure message changes. In most common usage
the summary is the list of hosts that are failing, so additional
hosts failing would remove an ack.
Period Definitions
Periods are used to define the conditions which should allow alerts to
be delivered.
period [label:] periodspec
A period groups one or more alarms and variables which control
how often an alert happens when there is a failure. The period
definition has two forms. The first takes an argument which is a
period specification from Patrick Ryanâs Time::Period Perl 5
module. Refer to "perldoc Time::Period" for more information.
The second form requires a label followed by a period specifica-
tion, as defined above. The label is a tag consisting of an
alphabetic character or underscore followed by zero or more
alphanumerics or underscores and ending with a colon. This form
allows multiple periods with the same period definition. One use
is to have a period definition which has no alertafter or
alertevery parameters for a particular time period, and another
for the same time period with a different set of alerts that
does contain those parameters.
Period definitions, in either the first or second form, must be
unique within each service definition. For example, if you need
to define two periods both for "wd {Sun-Sat}", then one or both
of the period definitions must specify a label such as "period
t1: wd {Sun-Sat}" and "period t2: wd {Sun-Sat}".
alertevery timeval [observe_detail | strict]
The alertevery keyword (within a period definition) takes the
same type of argument as the interval variable, and limits the
number of times an alert is sent when the service continues to
fail. For example, if the interval is "1h", then only the
alerts in the period section will only be triggered once every
hour. If the alertevery keyword is omitted in a period entry, an
alert will be sent out every time a failure is detected. By
default, if the summary output of two successive failures
changes, then the alertevery interval is overridden, and an
alert will be sent. If the string "observe_detail" is the last
argument, then both the summary and detail output lines will be
considered when comparing the output of successive failures. If
the string "strict" is the last argument, then the output of the
monitor or the state change of the service will have no effect
on when alerts are sent. That is, "alertevery 24h strict" will
send only one alert every 24 hours, no matter what. Please
refer to the ALERT DECISION LOGIC section for a detailed expla-
nation of how alerts are suppressed.
alertafter num
alertafter num timeval
alertafter timeval
The alertafter keyword (within a period section) has three
forms: only with the "num" argument, or with the "num timeval"
arguments, or only with the "timeval" argument. In the first
form, an alert will only be invoked after "num" consecutive
failures.
In the second form, the arguments are a positive integer fol-
lowed by an interval, as described by the interval variable
above. If these parameters are specified, then the alerts for
that period will only be called after that many failures happen
within that interval. For example, if alertafter is given the
arguments "3 30m", then the alert will be called if 3 failures
happen within 30 minutes.
In the third form, the argument is an interval, as described by
the interval variable above. Alerts for that period will only
be called if the service has been in a failure state for more
than the length of time desribed by the interval, regardless of
the number of failures noticed within that interval.
numalerts num
This variable tells the server to call no more than num alerts
during a failure. The alert counter is kept on a per-period
basis, and is reset upon each success.
no_comp_alerts
If this option is specified, then upalerts will be called when-
ever the service state changes from failure to success, rather
than only after a corresponding "down" alert.
alert alert [arg...]
A period may contain multiple alerts, which are triggered upon
failure of the service. An alert is specified with the alert
keyword, followed by an optional exit parameter, and arguments
which are interpreted the same as the monitor definition, but
without the ";;" exception. The exit parameter takes the form of
exit=x or exit=x-y and has the effect that the alert is only
called if the exit status of the monitor script falls within the
range of the exit parameter. If, for example, the alert line is
alert exit=10-20 mail.alert mis then mail-alert will only be
invoked with mis as its arguments if the monitor programâs exit
value is between 10 and 20. This feature allows you to trigger
different alerts at different severity levels (like when free
disk space goes from 8% to 3%).
See the ALERT PROGRAMS section above for a list of the pra-
maeters mon will pass automatically to alert programs.
upalert alert [arg...]
An upalert is the compliment of an alert. An upalert is called
when a services makes the state transition from failure to suc-
cess, if a corresponding "down" alert was previously sent. The
upalert script is called supplying the same parameters as the
alert script, with the addition of the -u parameter which is
simply used to let an alert script know that it is being called
as an upalert. Multiple upalerts may be specified for each
period definition. Set the per-period no_comp_alerts option to
send an upalert regardless if whether or not a "down" alert was
sent.
startupalert alert [arg...]
A startupalert is only called when the mon server starts execu-
tion, or when a "reset" command was issued to the server,
depending on the setting of the startupalerts_on_reset global.
Unlike other alerts, startupalerts are not called following the
exit of a monitor, i.e. they are called in their own right,
therefore the "exit=" argument is not applicable to startu-
palert.
upalertafter timeval
The upalertafter parameter is specified as a string that follows
the syntax of the interval parameter ("30s", "1m", etc.), and
controls the triggering of an upalert. If a service comes back
up after being down for a time greater than or equal to the
value of this option, an upalert will be called. Use this option
to prevent upalerts to be called because of "blips" (brief out-
ages).
AUTHENTICATION CONFIGURATION FILE
The file specified by the authfile variable in the configuration file
(or passed via the -A parameter) will be loaded upon startup. This
file defines restrictions upon which client commands may be executed by
which users. It is a text file which consists of comments, command def-
initions, and trap authentication parameters. A comment line begins
with optional whitespace followed by pound sign. Blank lines are
ignored.
The file is separated into a command section and a trap section. Sec-
tions are specified by a single line containing one of the following
statements:
command section
or
trap section
Lines following one of the above statements apply to that section until
either the end of the file or another section begins.
A command definition consists of a command, followed by a colon, fol-
lowed by a comma-separated list of users who may execute the command.
The default is that no users may execute any commands unless they are
explicitly allowed in this configuration file. For clarity, a user can
be denied by prefixing the user name with "!". If the word "AUTH_ANY"
is used for a username, then any authenticated user will be allowed to
execute the command. If the word "all" is used for a username, then
that command may be executed by any user, authenticated or not.
The trap section allows configuration of which users may send traps
from which hosts. The syntax is a source host (name or ip address),
whitespace, a username, whitespace, and a plaintext password for that
user. If the source host is "*", then allow traps from any host. If the
username is "*", then accept traps without regard for the username or
password. If no hosts or users are specified, then no traps will be
accepted.
An example configuration file:
command section
list: all
reset: root,admin
loadstate: root
savestate: root
trap section
127.0.0.1 root r@@tp4sswrd
This means that all clients are able to perform the list command,
"root" is able to perform "reset", "loadstate", "savestate", and
"admin" is able to execute the "reset" command.
CLIENT-SERVER INTERFACE
The server listens on TCP port 2583, which may be overridden using the
-p port option. Commands are a single line each, terminated by a new-
line. The server can handle any number of simultaneous client connec-
tions.
CLIENT INTERFACE COMMANDS
See manual page for moncmd.
MON TRAPPING
Mon has the facility to receive special "mon traps" from any local or
remote machine. Currently, the only available method for sending mon
traps are through the Mon::Client perl interface, though the UDP packet
format is defined well enough to permit the writing of traps in other
languages.
Traps are handled similarly to monitors: a trap sends an operational
status, summary line, and description text, and mon generates an alert
or upalert as necessary.
Traps can be caught by any watch/service group set up in the mon con-
figuration file, however it is suggested that you configure watch/ser-
vice groups specifically for the traps you expect to receive. When
defining a special watch/service group for traps, do not include a
"monitor" directive (as no monitor need be invoked). Since a monitor is
not being invoked, it is not necessary for the watch definition to have
a hostgroup which contains real host names. Just make up a useful
name, and mon will automatically create the watch group for you.
Here is a simple config file example:
watch trap-service
service host1-disks
description TRAP: for host1 disk status
period wd {Sun-Sat}
alert mail.alert someone@your.org
upalert mail.alert -u someone@your.org
Since mon listens on a UDP port for any trap, a default facility is
available for handling traps to unknown groups or services. To enable
this facility, you must include a "default" watch group with a
"default" service entry containing the specifics of alarms. If a
default/default watch group and service are not configured, then
unknown traps get logged via syslog, and no alarm is sent. NOTE: The
default/default facility is a single entity as far as accounting and
alarming go. Alarm programs which are not aware of this fact may send
confusing information when a failure trap comes from one machine, fol-
lowed by a success (ok) trap from a different machine. See the alarm
environment variable MON_TRAP_INTENDED above for a possible way around
this. It is intended that default/default be used as a facility to
catch unknown traps, and should not be relied upon to catch all traps
in a production environment. If you are lazy and only want to use
default/default for catching all traps, it would be best to disable
upalerts, and use the MON_TRAP_INTENDED environment variable in alert
scripts to make the alerts more meaningful to you.
Here is an example default facility:
watch default
service default
description Default trap service
period wd {Sun-Sat}
alert mail.alert someone@your.org
upalert mail.alert -u someone@your.org
EXAMPLES
The mon distribution comes with an example configuration called exam-
ple.cf. Refer to that file for more information.
SEE ALSO
moncmd(1), Time::Period(3pm), Mon::Client(3pm)
HISTORY
mon was written because I couldnât find anything out there that did
just what I needed, and nothing was worth modifying to add the features
I wanted. It doesnât have a cool name, and that bothers me because I
couldnât think of one.
BUGS
Report bugs to the email address below.
AUTHOR
Jim Trocki <trockij@arctic.org>
Linux $Date: 2007/06/03 13:08:59 $ mon(8)
