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 shouldn't
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 server's 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 arguments
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
particular resource which is provided by a group. Services are usually
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 'network-services' 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 determine
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
processed 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 scheduler
how frequently to invoke a monitor process. The scheduler may be temporarily
stopped. While it is stopped, client access still functions, but it just
doesn't schedule things. This is useful in conjunction while resetting the
server, because you can do this: save the hosts and services which are
disabled, reset the server with the scheduler 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 configuration
file, appended by the hosts from the applicable host group. For example, if
the watch group is "servers", which contain the hostnames
"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
parameters:
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
overridden 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 whitespace), 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 provide 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
previous one. This may be used by an alert script to provide historical
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
indicated by the cfbasedir global configuration variable.
"fping.monitor" should return an exit status of 0 if it completed
successfully (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
'a', or
alertdepend is set, and a parent dependency 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. Otherwise, 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 comparing the output from the previous monitor run to the
current and prevent 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
triggered 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 separated
entries of the trap's 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
indicated 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 parameters 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 global variable definitions,
zero or more hostgroup definitions, and one or more watch definitions. Each
watch definition may have one or more service definitions. A watch definition
is terminated by a blank line, another definition, or the end of the file. 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 ending 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 assembled into a single line.
Typically the configuration file has the following layout:
1. Global variable definitions
2. Hostgroup definitions
3. Watch definitions
See the "etc/example.cf" file which comes for the distribution for an
example.
Global Variables¶
The following variables may be set to override compiled-in defaults.
Command-line options will have a higher precedence than these definitions.
- 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 recognized 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 directory 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
authentication 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
configuration variable.
If type is pam, then PAM (pluggable authentication modules)
will be used for authentication. The service specified by the
pamservice 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
'username : password'. 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 follows (# 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 history 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 don't 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
scheduled until the interval defined in the respective service section.
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 command. 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 recursion (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 suppresses 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
prevent 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 multiple 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 characters, a
dash ("-"), a period ("."), or an underscore
("_"). Non-blank lines following the first hostgroup line are
interpreted as more hostnames. 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 composed 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 hostgroup
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.
A watch group is terminated by a blank line, the end of the file, or by a
subsequent definition, "watch", "hostgroup", or otherwise.
There may be a special watch group entry called "default". If a
default watch group is defined with a service entry named "default",
then this definition will be used in handling traps received for an
unrecognized watch and service.
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
definition 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 frequency 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 fraction, 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 intervals.
- 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
disabled 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 syntactical
rules. The expressions are evaluated in their own package space so as to
not accidentally have some unwanted side-effect. If a syntax error is
found when evaluating the expression, 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 specified service. These
opstatus substitutions are computed recursively, 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
invocations, or the suppression of individual hosts passed to the monitor.
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 status 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
expressions 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 keyword, depending on
the dep_behavior setting.
- dep_memory timeval
- If set, dep_memory will cause dependencies to continue to
prevent 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 monitoring 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 automatically 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 Ryan's Time::Period Perl 5 module.
Refer to "perldoc Time::Period" for more information.
The second form requires a label followed by a period specification, 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 explanation 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 followed 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 whenever 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 program's 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 pramaeters 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 success, 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 execution, 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 startupalert.
- 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 outages).
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 definitions, 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. Sections are
specified by a single line containing one of the following statements:
or
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, followed 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 newline. The server can handle any number of simultaneous client
connections.
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 configuration
file, however it is suggested that you configure watch/service 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, followed 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
example.cf. Refer to that file for more information.
SEE ALSO¶
moncmd(1),
Time::Period(3pm),
Mon::Client(3pm)
HISTORY¶
mon was written because I couldn't find anything out there that did just
what I needed, and nothing was worth modifying to add the features I wanted.
It doesn't have a cool name, and that bothers me because I couldn't think of
one.
BUGS¶
Report bugs to the email address below.
AUTHOR¶
Jim Trocki <trockij@arctic.org>