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caa(4)
NAME
caa - Cluster Application Availability (CAA) information
SYNOPSIS
Application resource profile:
TYPE=application
NAME=resource_name
[DESCRIPTION=description]
[CHECK_INTERVAL=check_interval]
[FAILURE_THRESHOLD=failure_threshold
FAILURE_INTERVAL=failure_interval]
[REQUIRED_RESOURCES=resource_list]
[OPTIONAL_RESOURCES=resource_list]
[PLACEMENT=placement_policy]
[HOSTING_MEMBERS=member_list]
[RESTART_ATTEMPTS=restart_attempts]
[FAILOVER_DELAY=failover_delay]
[AUTO_START={0|1}]
[ACTION_SCRIPT=action_script]
[SCRIPT_TIMEOUT=script_timeout]
[ACTIVE_PLACEMENT={0|1}]
Network resource profile:
TYPE=network
NAME=resource_name
[DESCRIPTION=description]
[FAILURE_THRESHOLD=failure_threshold
FAILURE_INTERVAL=failure_interval]
SUBNET=subnet_addr
OPERANDS
TYPE={application|network}
Resource type. Specify either application or network.
NAME=resource_name
Resource name. Specify a resource_name as a string containing
a combination of letters a-z, or A-Z, or digits 0-9.
[DESCRIPTION=description]
Resource description string.
[CHECK_INTERVAL=check_interval]
Time (in seconds) at which the check entry point of the application's
action script runs. The check interval is the maximum amount of time an
application can be unavailable to clients before CAA attempts to
restart it. If you do not supply a check interval, it defaults to 60
seconds.
[FAILURE_THRESHOLD=failure_threshold]
(reserved for future use)
[FAILURE_INTERVAL=failure_interval]
(reserved for future use)
[REQUIRED_RESOURCES=resource_list]
Ordered list of resources, separated by white space, on which the
application depends. These resources must be active on any member on
which the application is running, or must be application resources that
may be started on the cluster member. If you don't specify a required
resources list, CAA imposes no required dependencies upon the
application resource.
CAA uses the required resources list, in conjunction with the failover
policy and hosting members list, to determine which members are
eligible to host the application resource. It also uses the required
resources list to start required application resources when the
caa_start command is run.
A failure of a required resource on the hosting member, will cause CAA
to initiate failover of the application. This could cause CAA to fail
the application resource over to another member that provides the
resource or to stop the application. In the latter case, CAA continues
to monitor the required resources and restarts the application when the
resource is again available in the cluster.
[OPTIONAL_RESOURCES=resource_list]
(reserved for future use)
[PLACEMENT=placement_policy]
Policy according to which CAA selects the member on which to start or
restart the application resource. CAA uses the placement policy in
conjunction with the resource's required list. You can specify any one
of the following as a placement policy:
balanced The balanced application resources are distributed equally
among all active members if no optional resources are listed.
favored CAA refers to the hosting members list before starting or
restarting the application resource. First, the member on
the hosting members list is chosen based on optional
resources, see OPTIONAL RESOURCES for more information. If a
member cannot be chosen based on optional resources, the
first member on the list is most favored to run the service.
If that member is unavailable, the second member on the list
is the most favored, and so on. If all members on the hosting
members list are unavailable, CAA favors placing the
application resource on the member currently running the
fewest application resources.
You must specify a hosting members list when you select a
favored placement policy.
restricted
Similar to the favored placement policy, except that if all
members on the hosting members list are unavailable, CAA will
not start or restart the application resource. A restricted
placement policy ensures that the resource will never run on
a member that is not on the list, unless you manually
relocate it to that member.
You must specify a hosting members list when you select a
restricted placement policy.
If you do not specify a placement policy, CAA uses a balanced placement
policy for the application resource by default.
[HOSTING_MEMBERS=member_list]
Hosting members list. Specify an ordered list of members, separated by
white space, that can host the application resource. If you specify a
placement policy of favored or restricted, you must also specify a
hosting members list.
CAA uses the hosting members list in conjunction with the application
resource's placement policy. After optional resources are considered,
Applications are placed on hosts in the order in which they are listed
in the hosting members list.
[RESTART_ATTEMPTS=restart_attempts]
(reserved for future use)
[FAILOVER_DELAY=failover_delay]
(reserved for future use)
[AUTO_START={0|1}]
(reserved for future use)
[ACTION_SCRIPT=action_script]
User-written action script for the application resource. The format of
CAA action scripts is similar to that of system init files located in
the /sbin/init.d directory. The script file performs user-defined
tasks and can invoke other scripts and executable programs.
An action script has the following entry points:
start Called by CAA to start or restart the application resource.
The start entry point executes all commands necessary to
start the application and must return 0 (zero) for success
and a nonzero value for failure.
stop Called by CAA to stop a running application resource. It is
not called when stopping a suspended application resource
(see caa_stop(8) for details). The stop entry point executes
all commands necessary to stop the application and must
return 0 (zero) for success and a nonzero value for failure.
check (reserved for future use)
You can specify either a full pathname for the script file, or its
filename (in which case CAA looks for the file in the
/var/cluster/caa/script directory). If you do not specify an action
script, CAA looks for an action script named
/var/cluster/caa/script/resource_name.scr.
SUBNET=subnet_addr
Subnet address of a network resource. Specify the subnet address in
xxx.xxx.xxx.0 format (for example, 16.140.112.0).
DESCRIPTION
CAA tracks the state of the members in a cluster and resources in a cluster
(such as networks and applications). CAA monitors the needs of application
resources in a cluster and ensures that applications run on members that
meet their needs. If the cluster member on which an application is running
fails, or if a particular resource that another resource requires fails,
CAA relocates the application to another member that has the required
resources available.
CAA allows you to enhance overall application performance by balancing
application execution among a set of available cluster members.
CAA manages both application and network resources. You must have root
privileges to use most CAA commands. Only, the caa_stat command does not
require root priviliges.
CAA consists of components that work together to make application resources
highly available:
· A resource manager comprised of the run-time CAA daemons (caad) on all
cluster members. The resource manager starts, stops, relocates, and
restarts application resources when failure conditions occur.
· A user interface that allows you to manage application and network
resources in a cluster.
The commands available with the command-line interface are listed in
the SEE ALSO section of this reference page. The SysMan menu provides
a graphical user interface (GUI) for performing system management
tasks for the cluster, cluster members, and CAA applications. For
more information on using SysMan, see sysman(8) and the online help
available for the sysman application.
· Resources that are managed and monitored by CAA which may have
dependencies on each other. A resource is defined by its resource
profile.
· Action scripts associated with resources that are used by CAA to start
and stop the application resources.
A resource profile is an ASCII text file that assigns values to attributes
that define how a resource should be managed or monitored in a cluster. The
attributes described in the SYNOPSIS and OPERANDS section of this reference
page make up a profile.
Create a resource profile by using the caa_profile(8) command, the Profile
Management item under the SysMan Menu, or a text editor. The type of
resource (application or network determines which keywords and operands you
can specify in its profile. Profiles are written to the
/var/cluster/caa/profile directory by caa_profile. CAA expects all resource
profiles to be in the /var/cluster/caa/profile directory.
When you create a resource profile with a text editor, you can omit
optional keywords and operands (for example, REQUIRED_RESOURCES and RESTART
ATTEMPTS). There are default values for most keywords.
You can also update a resource profile with a text editor. Any time you
edit a profile by hand, you should validate the profile with the
caa_profile -validate command. Using the caa_register -u command, you can
then update the resource while the resource remains online. Only certain
keyword settings can be updated:
You cannot update the NAME or TYPE of any resource. You cannot update the
SUBNET address of a network resource.
You can update:
ACTION_SCRIPT
Changes to the action script location and contents take effect
the next time CAA uses the script.
DESCRIPTION
Changes to the description take place immediately.
HOSTING_MEMBERS
Changes to the hosting members list take place the next time the
placement policy is executed.
REQUIRED_RESOURCES
Changes to the required resource list take place the next time
the placement policy is executed.
OPTIONAL_RESOURCES
Changes to the optional resource list take place the next time
the placement policy is executed.
PLACEMENT Changes to the placement policy take place the next time the
placement policy is executed.
AUTO_START
Changes to auto-start take effect after the next cluster reboot.
CHECK_INTERVAL
Changes to the check interval take effect immediately and reset
the check interval timer.
FAILURE_THRESHOLD
Changes to the failure threshold take effect immediately.
FAILURE_INTERVAL
Changes to the failure interval take effect immediately.
RESTART_ATTEMPTS
Changes to the restart attempts take place the next time the
placement policy is executed.
FAILOVER_DELAY
Changes to the failover delay take effect immediately.
CAA does extensive logging of its actions to both the command line and the
EVM event management system. To monitor CAA related EVM events, see the
examples below. See the EVM(5) reference page for details on how to use the
EVM event management system.
If a CAA daemon is busy and cannot process the caa_start/caa_stop request
immediately, a message that the daemon is busy is displayed and the request
is queued for processing once the daemon is free.
EXAMPLES
The following is an example of an application resource profile:
TYPE = application
NAME = xclock
CHECK_INTERVAL = 60
FAILURE_THRESHOLD = 0
FAILURE_INTERVAL = 0
REQUIRED_RESOURCES =
OPTIONAL_RESOURCES =
HOSTING_MEMBERS =
PLACEMENT = balanced
RESTART_ATTEMPTS = 1
FAILOVER_DELAY = 0
AUTO_START = 0
ACTION_SCRIPT = xclock.scr
SCRIPT_TIMEOUT = 90
ACTIVE_PLACEMENT = 0
The following is an example of an network resource profile:
TYPE = network
NAME = net1
CHECK_INTERVAL =
FAILURE_THRESHOLD = 0
FAILURE_INTERVAL = 0
SUBNET = 16.140.112.0
The following is an example action script:
#!/usr/bin/ksh -p
#
PATH=/sbin:/usr/sbin:/usr/bin
export PATH
CAATMPDIR=/var/cluster/caa/tmp
CMDPATH=/usr/bin/X11/xclock
CMD=`basename $CMDPATH`
case $1 in
'start')
if [ -f $CMDPATH ]; then
$CMDPATH &
exit 0
else
exit 1
fi
;;
'stop')
ps -e -o pid,command | while read pid command args
do
case "${command}" in
${CMDPATH}|${CMD})
kill -TERM $pid
exit 0
;;
esac
done
exit 1
;;
'check')
PIDLIST=`ps ax | egrep $CMDPATH | egrep -v 'grep' | awk '{print
$1}'`
if [ -z "$PIDLIST" ]; then
PIDLIST=`ps ax | egrep $CMD | egrep -v 'grep' | awk '{pr
int $1}'`
fi
if [-n "$PIDLIST" ]; then
exit 0
else
exit 1
fi
;;
esac
To monitor CAA events on the console, use the following command:
# evmwatch | evmshow -f "[name *.caa.*]"
To view events related to CAA that have been sent to the EVM Event
Management System:
# evmget | evmshow -f "[name *.caa.*]"
SEE ALSO
Commands: caa_profile(8), caa_register(8), caa_relocate(8), caa_start(8),
caa_stat(1), caa_stop(8), caa_unregister(8)
Daemon: caad(8)
TruCluster Server Cluster Administration
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Index for
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