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WebSphere Extended Deployment ObjectGrid v6.1 introduces a dynamic deployment topology. The deployment policy descriptor is used to manage deployment into this environment.
The deployment policy is encoded as an XML file that is provided to an ObjectGrid container. The XML file specifies the following information:
- The maps belonging to each map set
- The number of partitions
- The number of synchronous and asynchronous replicas
The deployment policy also controls the following placement behaviors:
- The minimum number of active containers before placement commences
- Automatic replacement of lost shards
- Placement of each shard from a single partition onto a different machine
Endpoint information is not pre-configured in the dynamic environment. There are no server names or physical topology information found in the deployment policy. All shards in a dynamic grid are automatically placed into ObjectGrid containers by the catalog service. The catalog service uses the constraints defined by the deployment policy to automatically manage shard placement. This allows very large grids to be easily configured. It also allows you to add servers to your environment as needed. For more information, see introduction to catalog services.
Note that in a WebSphere Application Server environment, a core-group size of more than 50 members is not supported. For more information on this limitation, see core group scaling considerations.
A deployment policy XML file is passed to an ObjectGrid container during start-up. A deployment policy must be used in tandem with an ObjectGrid XML file. The deployment policy is not required to start a container, but is recommended. The deployment policy must be compatible with the ObjectGrid XML that is used with it. For each objectgridDeployment in the deployment policy, you must have a corresponding objectGrid in your ObjectGrid XML. The maps within the objectgridDeployment must be consistent with the backingMaps found in the ObjectGrid XML. Every backingMap must be referenced within one and only one mapSet.
Following is an example deployment policy. This deployment policy is intended to be paired with the corresponding ObjectGrid XML, companyGrid.xml
<?xml version="1.0" encoding="UTF-8"?>
<deploymentPolicy xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://ibm.com/ws/objectgrid/deploymentPolicy ../deploymentPolicy.xsd"
xmlns="http://ibm.com/ws/objectgrid/deploymentPolicy">
<objectgridDeployment objectgridName="CompanyGrid">
<mapSet name="mapSet1" numberOfPartitions="11"
minSyncReplicas="1" maxSyncReplicas="1"
maxAsyncReplicas="0" numInitialContainers="4">
<map ref="Customer" />
<map ref="Item" />
<map ref="OrderLine" />
<map ref="Order" />
</mapSet>
</objectgridDeployment>
</deploymentPolicy>
The companyGridDpReplication.xml file has 1 mapSet that is divided into 11 partitions. Each partition must have exactly 1 synchronous replica. This is dictated by the minSyncReplicas and maxSyncReplicas attributes. Since minSyncReplicas is set to 1, each partition in the mapSet must have at least 1 synchronous replica available in order to process write transactions. Since maxSyncReplicas is set to 1, each partition must not exceed 1 synchronous replica. The partitions in this mapSet have no asynchronous replicas.
The numInitialContainers instructs the catalog service to defer placement until 4 containers are available to support this ObjectGrid. The numInitialContainers is ignored once that number has been reached.
The companyGridDpReplication.xml file demonstrates a common way to configure a deployment policy, but a deployment policy can offer even more control over how and when your ObjectGrid is deployed into your environment. For a complete description of the deployment policy descriptor file, see Deployment policy configuration reference.
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