Data services utilize several types of resources: applications such as Apache Web Server or Sun ONE Web Server utilize network addresses (logical hostnames and shared addresses) upon which the applications depend. Application and network resources form a basic unit that is managed by the RGM.
Data services are resource types. For example, Sun Cluster HA for Oracle is the resource type SUNW.oracle-server and Sun Cluster HA for Apache is the resource type SUNW.apache.
A resource is an instantiation of a resource type that is defined cluster wide. There are several resource types defined.
Network resources are either SUNW.LogicalHostname or SUNW.SharedAddress resource types. These two resource types are pre-registered by the Sun Cluster software.
The SUNW.HAStorage and HAStoragePlus resource types are used to synchronize the startup of resources and disk device groups upon which the resources depend. It ensures that before a data service starts, the paths to cluster file system mount points, global devices, and device group names are available. For more information, see “Synchronizing the Startups Between Resource Groups and Disk Device Groups” in the Sun Cluster 3.1 Data Service Planning and Administration Guide. (The HAStoragePlus resource type became available in Sun Cluster 3.0 5/02 and added another feature, enabling local file systems to be highly available. For more information on this feature, see HAStoragePlus Resource Type.)
RGM-managed resources are placed into groups, called resource groups, so that they can be managed as a unit. A resource group is migrated as a unit if a failover or switchover is initiated on the resource group.
When you bring a resource group containing application resources online, the application is started. The data service start method waits until the application is up and running before exiting successfully. The determination of when the application is up and running is accomplished the same way the data service fault monitor determines that a data service is serving clients. Refer to the Sun Cluster 3.1 Data Service Planning and Administration Guide for more information on this process.
The RGM controls data services (applications) as resources, which are managed by resource type implementations. These implementations are either supplied by Sun or created by a developer with a generic data service template, the Data Service Development Library API (DSDL API), or the Resource Management API (RMAPI). The cluster administrator creates and manages resources in containers called resource groups. The RGM stops and starts resource groups on selected nodes in response to cluster membership changes.
The RGM acts on resources and resource groups. RGM actions cause resources and resource groups to move between online and offline states. A complete description of the states and settings that can be applied to resources and resource groups is in the section Resource and Resource Group States and Settings. Refer to Resources, Resource Groups, and Resource Types for information about how to launch a resource management project under RGM control.
An administrator applies static settings to resources and resource groups. These settings can only be changed through administrative actions. The RGM moves resource groups between dynamic “states.” These settings and states are described in the following list.
Managed or unmanaged. These are cluster-wide settings that apply only to resource groups. Resource groups are managed by the RGM. The scrgadm(1M) command can be used to cause the RGM to manage or to unmanage a resource group. These settings do not change with a cluster reconfiguration.
When a resource group is first created, it is unmanaged. It must be managed before any resources placed in the group can become active.
In some data services, for example a scalable web server, work must be done prior to starting up network resources and after they are stopped. This work is done by initialization (INIT) and finish (FINI) data service methods. The INIT methods only run if the resource group in which the resources reside is in the managed state.
When a resource group is moved from unmanaged to managed, any registered INIT methods for the group are run on the resources in the group.
When a resource group is moved from managed to unmanaged, any registered FINI methods are called to perform cleanup.
The most common use of INIT and FINI methods are for network resources for scalable services, but they can be used for any initialization or cleanup work that is not done by the application.
Enabled or disabled. These are cluster-wide settings that apply to resources. The scrgadm(1M) command can be used to enable or disable a resource. These settings do not change with a cluster reconfiguration.
The normal setting for a resource is that it is enabled and actively running in the system.
If for some reason, you want to make the resource unavailable on all cluster nodes, you disable the resource. A disabled resource is not available for general use.
Online or offline. These are dynamic states that apply to both resource and resource groups.
These states change as the cluster transitions through cluster reconfiguration steps during switchover or failover. They can also be changed through administrative actions. The scswitch(1M) can be used to change the online or offline state of a resource or resource group.
A failover resource or resource group can only be online on one node at any time. A scalable resource or resource group can be online on some nodes and offline on others. During a switchover or failover, resource groups and the resources within them are taken offline on one node and then brought online on another node.
If a resource group is offline then all of its resources are offline. If a resource group is online, then all of its enabled resources are online.
Resource groups can contain several resources, with dependencies between resources. These dependencies require that the resources be brought online and offline in a particular order. The methods used to bring resources online and offline might take different amounts of time for each resource. Because of resource dependencies and start and stop time differences, resources within a single resource group can have different online and offline states during a cluster reconfiguration.
You can configure property values for resources and resource groups for your SunPlex data services. Standard properties are common to all data services. Extension properties are specific to each data service. Some standard and extension properties are configured with default settings so that you do not have to modify them. Others need to be set as part of the process of creating and configuring resources. The documentation for each data service specifies which resource properties can be set and how to set them.
The standard properties are used to configure resource and resource group properties that are usually independent of any particular data service. The set of standard properties is described in an appendix to the Sun Cluster 3.1 Data Service Planning and Administration Guide.
The RGM extension properties provide information such as the location of application binaries and configuration files. You modify extension properties as you configure your data services. The set of extension properties is described in the Sun Cluster 3.1 Data Service Planning and Administration Guide.