By default, Fuse Message Broker uses store-based cursors for persistent messages and file-based cursors for non-persistent messages. You can, however, configure your destinations to use a specified cursor implementation by adding the appropriate policy entries into the destination's policy map.
You configure a destination's policy set using a destinationPolicy
element. The destinationPolicy
element is a wrapper for a policyMap
element. The policyMap
element is a wrapper for a policyEntries
element. The policyEntries
element is a wrapper for one or more policyEntry
elements.
The cursor policies are entered as children to a policyEntry
element. The configuration elements used to specify the type of destination you are configuring. Topics use cursors for both durable subscribers and transient subscribers, so it uses two sets of configuration elements. Queues only a single cursor and only require a single set of configuration elements.
Topics maintain a dispatch queue and a pending cursor for every consumer subscribed to the topic regardless of whether the subscription is durable or transient. You can configure the cursor implementation used by durable subscribers separately from the cursor implementation used by transient subscribers.
You configure the cursor implementation used by durable subscribers by adding
PendingDurableSubscriberMessageStoragePolicy
child element to the topic's
policyEntry
element. Table 4.1 describes the possible
children of PendingDurableSubscriberMessageStoragePolicy
.
Table 4.1. Elements for Configuring the Type of Cursor to Use for Durable Subscribers
Element | Description |
---|---|
vmDurableCursor
| Specifies the VM cursors will be used. See VM cursors for more information. |
fileDurableSubscriberCursor
| Specifies that file-based cursors will be used. See File-based cursors for more information. |
You configure the cursor implementation used by transient subscribers by adding pendingSubscriberPolicy
child element to the topic's policyEntry
element. Table 4.2 describes the possible children of pendingSubscriberPolicy
.
Table 4.2. Elements for Configuring the Type of Cursor to Use for Transient Subscribers
Element | Description |
---|---|
vmCursor
| Specifies the VM cursors will be used. See VM cursors for more information. |
fileCursor
| Specifies that file-based cursors will be used. See File-based cursors for more information. |
Example 4.1 shows a configuration snip-it that configures a topic to use VM cursors for its transient subscribers and file-based cursors for its durable subscribers.
Example 4.1. Configuring a Topic's Cursor Usage
<beans ... > <broker ... > ... <destinationPolicy> <policyMap> <policyEntries> <policyEntry topic="com.fusesource.>"> ... <pendingSubscriberPolicy> <vmCursor /> </pendingSubscriberPolicy> <PendingDurableSubscriberMessageStoragePolicy> <fileDurableSubscriberPolicy /> </PendingDurableSubscriberMessageStoragePolicy> ... </policyEntry> ... </policyEntries> </policyMap> </destinationPolicy> ... </broker> ... </beans>
Queues use a single pending cursor and dispatch queue. You configure the type of cursor to use by adding a
pendingQueuePolicy
element to the queue's policyEntry
element.
Table 4.3 describes the possible children elements of the
pendingQueuePolicy
element.
Table 4.3. Elements for Configuring the Type of Cursor to Use for a Queue
Element | Description |
---|---|
vmQueueCursor
| Specifies the VM cursors will be used. See VM cursors for more information. |
fileQueueCursor
| Specifies that file-based cursors will be used. See File-based cursors for more information. |
Example 4.2 shows a configuration snippet that configures a queue to use VM cursors.
Example 4.2. Configuring a Queue's Cursor Usage
<beans ... > <broker ... > ... <destinationPolicy> <policyMap> <policyEntries> <policyEntry queue="com.fusesource.>"> ... <pendingQueuePolicy> <vmQueueCursor /> </pendingQueuePolicy> ... </policyEntry> ... </policyEntries> </policyMap> </destinationPolicy> ... </broker> ... </beans>