Creating a health policy: Define health policy general properties
Use this page to create health policies, which are used
to perform a variety of health-based assessments on clusters, dynamic
clusters, and application server instances running on nodes.
To view this administrative console page, click .
Privileges for health policies differ, depending on the user’s
administrative role. Roles include monitor, operator, configurator,
and administrator. If you are a user with either a monitor or an
operator role, you can only view health policy information. If you
are a user with either a configurator or an administrator role, you
have all configuration privileges for health policies.
When you complete all of the required fields, click Next to
proceed.
- Name
Specifies the name of a health policy. The health policy
name is required and must be unique among all the health policies
in the cell.
The name cannot begin with a period (.)
or a space. A space does not generate an error, but leading and trailing
spaces are automatically deleted. Use meaningful and consistent health
policy names. For example, age-based health policies can be indicated
by naming the policies AGE_20DAYS, AGE_15DAYS,
and so on.
- Description
Specifies an additional description of the health policy.
The description is optional. You can edit the description when you
are creating or editing a health policy. Consider using the optional
description when you are using many health policies or when multiple
administrators manage the same set of health policies.
- Predefined health condition
The health condition defines the specific policy that is
implemented. Predefined health conditions are those that ship with
WebSphere Virtual Enterprise.
Some policies are prevention-based and some are detection-based.
Prevention-based policies are used to avoid conditions that might
lead to problems, while the detection-based policies are used to identify
existing conditions and to achieve resolution. These policies can
be used to perform health-based assessments on clusters, dynamic clusters,
and application server instances running on nodes. In the case of
dynamic clusters, regardless of the health policy that you are using,
the minimum number of dynamic cluster instances remains running.
- The age-based condition policy restarts the associated
members when their age reaches a certain user-defined value. This
restart cleans out all cached and memory acquired data. If you select
age-based condition policy, you must define the age criteria. The age-based condition is supported for all server
types.
- The excessive request timeout condition policy tracks the
memory that is used for request timeouts. When the percentage of timeouts
exceeds the breach of condition, the members are restarted. If you
select the excessive request timeout condition, you must set the memory
used percentage threshold. The excessive request
timeout condition is supported for all server types.
Restriction: The excessive request timeout condition does not
apply to Java Message Service (JMS) and Internet Inter-ORB Protocol
(IIOP) traffic.
- The excessive response time condition policy tracks the
requests and the amount of time they take to complete. Use this policy
to clean up servers that have an average number of requests that take
longer than a specified time. If an average number of requests takes
longer than a certain amount of time, the members are restarted. When
you select the excessive response time policy, you must define the
response time threshold. The excessive response
time condition is supported for all server types.
- The memory condition: excessive memory usage policy tracks
the memory usage for a member. When the memory usage exceeds a percentage
of the heap size for a specified time, actions are taken to correct
this situation. If you define the health policy against a standalone
server, static cluster, or dynamic cluster in manual mode, then the
member stops and restarts. If you define the health policy against
a dynamic cluster that is in automatic or supervised mode, then the
member that is flagged by the condition stops. The placement controller
dynamically decides which, if any, servers to start based on its evaluation
of the environment. These actions occur automatically if you are in
automatic mode. If you are in supervised mode, you can approve the
runtime tasks are generated to correct the situation. If you select
the excessive memory usage policy, you must define the memory used
and the time-over-memory threshold. The excessive
memory usage condition is supported only on application servers on
nodes that run WebSphere Application Server or
WebSphere Application Server Community Edition. You cannot define
the excessive memory usage condition for other middleware server types.
- The memory condition: memory leak policy tracks consistent
downward trends in free memory that is available to a server in the
Java heap. The detection level setting determines when these trends
are detected. If you select the memory condition: memory leak policy,
you must define a detection level. The slower detection level setting
requires the most historical data. The normal and faster detection
level settings require the same amount of historical data, but the
faster setting allows analysis before the Java heap has expanded to
its maximum configured size. This provides earlier detection capability,
but is also more prone to false positives. This condition supports
heap dumps in addition to server restarts as reactions. The memory leak condition is not supported for
other middleware server types.
- The storm drain condition policy tracks stuck requests.
The server that is associated with this policy restarts when the specified
detection level is reached. Storm drain detection relies on change
point detection on a given time series data. The metrics that are
used for detecting storm drain are the response times and deployment
workload manager weights that are observed for the server. The storm
drain condition applies only to dynamic clusters and cells. If you
select the storm drain condition policy, you must select the detection
level.
To detect change points, the health controller calculates
a left mean and a right mean for a given point. For a point, the left
mean consists of the mean value of N samples that arrive prior
to this sample, and the right mean is the mean value of N samples,
including the current point, that arrive later. The difference of
the left and the right mean values is stored and compared with other
differences in a set of values to N to determine if this difference
is a local maxima. If this difference is the maximum difference, then
the point to which this difference corresponds, is declared as a change
point. The two metrics that are used for detecting storm drain
are the response times and dynamic workload manager weights that are
observed for the server.
The storm drain
condition is supported for all server types.Restriction: The
storm drain condition does not apply to JMS and IIOP traffic.
- The workload condition policy restarts the members when
a certain user-defined number of requests are serviced. This policy
cleans out the memory and caches. If you select the workload policy,
you must define the total request criteria. The
workload condition is supported for all server types.
- Custom health condition
You can define health conditions if the existing health
conditions do not fit your needs. Custom health conditions can be
tested against metrics in your environment.
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