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caa(4)
NAME
caa - Cluster Application Availability (CAA) information
SYNOPSIS
Application resource profile:
NAME=resource_name
TYPE=application
[ACTION_SCRIPT=action_script]
[ACTIVE_PLACEMENT={0|1}]
[AUTO_START={0|1}]
[CHECK_INTERVAL=check_interval]
[DESCRIPTION=description]
[FAILOVER_DELAY=failover_delay]
[FAILURE_INTERVAL=failure_interval
FAILURE_THRESHOLD=failure_threshold]
[HOSTING_MEMBERS=member_list]
[OPTIONAL_RESOURCES=resource_list]
[PLACEMENT=placement_policy]
[REQUIRED_RESOURCES=resource_list]
[RESTART_ATTEMPTS=restart_attempts]
[SCRIPT_TIMEOUT=script_timeout]
Network resource profile:
NAME=resource_name
TYPE=network
[DESCRIPTION=description]
[FAILURE_INTERVAL=failure_interval
FAILURE_THRESHOLD=failure_threshold]
SUBNET=subnet_addr
Tape resource profile:
NAME=resource_name
TYPE=tape
[DESCRIPTION=description]
DEVICE_NAME=device_name
[FAILURE_INTERVAL=failure_interval
FAILURE_THRESHOLD=failure_threshold]
Media Changer resource profile:
TYPE=changer
NAME=resource_name
[DESCRIPTION=description]
DEVICE_NAME=device_name
[FAILURE_INTERVAL=failure_interval
FAILURE_THRESHOLD=failure_threshold]
DEVICE_NAME=device_name
OPERANDS
TYPE={application|network|tape|changer}
Resource type. Specify either application, network, tape or changer.
NAME=resource_name
Resource name. Specify a resource_name as a string containing a
combination of characters [a-z, A-Z, 0-9, '.','_']. The resource name
may not start with a period (.).
[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. A check interval of 0 means never check the resource.
[FAILURE_THRESHOLD=failure_threshold]
Number of times CAA may detect a resource failure within the failure
interval before it marks the resource unavailable and stops monitoring
it. If you do not specify a failure threshold, CAA uses a default
failure threshold of 0 (zero), which turns off failure threshold
monitoring.
[FAILURE_INTERVAL=failure_interval]
Time (in seconds) during which the failure threshold is tallied and
applied. If you do not specify a failure threshold, CAA uses a default
failure interval of 0 (zero), which turns off failure threshold
monitoring. Specifying a nonzero failure interval is meaningless unless
failure threshold is also nonzero.
[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 placement
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 with the -f option.
A failure of a required resource on the hosting member, will cause CAA
to initiate relocation of the application if the failed resource is
available or can be started on another member. This could cause CAA to
fail the application resource over to another member that provides the
resource or to stop the application if there is no member that provides
the resource. 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]
Ordered list of optional resources, separated by white space.
CAA uses the optional resources list, in conjunction with the required
resources list, placement policy, and hosting members list, to
determine the optimal member to host the application resource when more
than one member is eligible to host the resource. Optional resources
must be in the state ONLINE on a cluster member to affect resource
placement. The cluster member with the most optional resources is used
to run the application. If the hosting members list is not empty, the
cluster member in the list with the most optional resources is used.
If the number of optional resources on cluster members is equal, the
member running the resource with the earliest placement in the list is
used to run the application. The number of optional resources per
resource is limited to 58.
A failure of an optional resource on the hosting member does not
initiate application relocation.
[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 CAA favors starting or restarting the application resource on
a member based on the optional resources listed, see OPTIONAL
RESOURCES for more information. If there are no optional
resources listed the member with currently running the fewest
application resources is chosen. 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, a 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, even if you attempt to
explicitly 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.
[ACTIVE_PLACEMENT={0|1}]
Reevaluates the placement of an application resource when a cluster
member joins the cluster.
[RESTART_ATTEMPTS=restart_attempts]
Number of times CAA attempts to restart the resource on the current
member before attempting to relocate it elsewhere. The default number
of restart attempts is 1.
[FAILOVER_DELAY=failover_delay]
Number of seconds CAA waits before attempting to relocate the
application resource due to a host failure. If the original cluster
member becomes available to run the application resource within the
FAILOVER_DELAY time, the application will restart on that member. The
default failover delay is 0 (zero) seconds.
[AUTO_START={0|1}]
When set to 1, start the application resource automatically after a
cluster reboot, regardless of whether it had been stopped or running
before the reboot. When set to 0, start the application resource
automatically only if it had been running before the reboot. The
default is 0.
[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 an UNKNOWN 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. The stop
entry point should consider an attempt to stop an application
that is not running a success and return 0 (zero).
check Called by CAA periodically (according to the resource's check
interval) to determine the health of the application
resource. The check entry point executes all commands
necessary to determine whether the application is still
running and must return 0 (zero) for success and a nonzero
value for failure. If the check entry point returns failure,
CAA initiates relocation for the application resource.
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.
[SCRIPT_TIMEOUT=script_timeout]
The maximum time for an action script to execute. An error message is
returned if the script does not finish executing within the time (in
seconds) specified. The timeout applies to all action script entry
points (start, stop, and check). If this value is not specified CAA
assumes a default value of 60 seconds.
SUBNET=subnet_addr
Subnet address of a network resource. Specify the subnet address in
xxx.xxx.xxx.xxx format (for example, 16.140.112.0). The network is the
bitwise AND of the IP address and the netmask. If you consider IP
address of 16.69.225.12 and a netmask of 255.255.255.0 the subnet will
be 16.69.225.0
DEVICE_NAME=device_name
Device name of a tape or media changer device. Specify either the full
path of the device (for example, /dev/tape/tape1) or just the device
name.
DESCRIPTION
CAA tracks the state of the members in a cluster and resources in a cluster
(such as networks and applications). CAA monitors the requirements of
application resources in a cluster and ensures that applications run on
members that meet their requirements. 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 can start a group of application resources with one call of the
caa_start command. CAA will start all required application resources in the
order they are listed in the resource profile if they are available to be
started.
CAA allows you to enhance overall application performance by balancing
application execution among a set of available cluster members.
CAA manages application, network, tape, and changer 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 and monitor other resources:
· 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.
· Resource monitors that are used to check on the state of a particular
type of resource. Resource monitors are located in the directory
/var/cluster/caa/monitors.
· 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. A resource is defined
by its resource profile. A resource profile defines to CAA how a
application or network resource should run in a cluster. The
caa_profile command creates new resource profiles, either with default
values or fully customized according to command-line values. It can
also validate, update, or delete profiles.
· 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 Cluster
Application Availability (CAA) Management branch under TruCluster Specific
on the SysMan Menu, or a text editor. The type of resource (application,
network, tape, or changer 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 operands and keywords. There are default values for most keywords.
Resources must be registered with CAA, using the caa_register command,
after a profile is created. CAA can only begin to monitor and manage a
resource after it has been registered.
After a resource has been registered, the information in the profile is
contained in the Registry Database located at
/var/cluster/caa/registry/caa.reg. This file should never be edited with a
text editor.
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 to check that the profile is syntactically
correct. Using the caa_register -u command, you can then update the
resource while the resource remains online. If you change the profile and
do not update the registration, the Registry Database will not contain the
new profile information.
Only certain keyword settings can be updated:
You cannot update the NAME or TYPE of any 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 at the next failure.
FAILURE_INTERVAL
Changes to the failure interval take effect at the next failure.
RESTART_ATTEMPTS
Changes to the restart attempts take place at the next failure.
FAILOVER_DELAY
Changes to the failover delay take effect at the next failure.
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.
EXAMPLES
The following is an example of an application resource profile:
TYPE = application
NAME = clock
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 = clock.scr
SCRIPT_TIMEOUT = 60
ACTIVE_PLACEMENT = 0
The following is an example of a network resource:
TYPE = network
NAME = net1
CHECK_INTERVAL = 60
FAILURE_THRESHOLD = 0
FAILURE_INTERVAL = 0
SUBNET = 16.140.112.0
For examples of action scripts see the directory /var/cluster/caa/script or
/var/cluster/caa/examples.
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)
Files: /var/cluster/caa/script, /var/cluster/caa/profile,
/var/cluster/caa/registry, /var/cluster/caa/monitors,
/var/cluster/caa/examples
TruCluster Server Cluster Administration
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