PersisterPool is a JMS message consumer that creates, destroys and maintains multiple pools of on-demand persisters. It listens to an XQueue for requests carried by ObjectMessages. The incoming message is supposed to contain a task map with the URI and a transmit XQueue, etc. PersisterPool evaluates the URI to figure out the details of the request. If the request is to ask for a new persister, it first looks up the classname of the implementation based on the URI and the given properties. Then PersisterPool tries to check out the pool of the classname from the cache. If there exists the persister pool for the implementation, it just checks out a new instance of the persister with the given properties. Otherwise, PersisterPool will create a new pool for the classname and checks out a new instance of the persister from it. It then starts up a new thread on the persister and returns the thread back. The requester is supposed to monitor the status of the thread in order to tell the status of the persister. The requester is also able to control the persister via the associated transmit queue. PersisterPool will frequently monitor the status of all active persisters in every heartbeat. If any one of them is stopped or closed, PersisterPool will checkin the persister and clean up the cache. If the request is to return the used thread, it will check in both the thread and the persister.

URI is used to identify the destination and the implementation. PersisterPool parses the URI string and creates a map with all XML properties from the key-value pairs specified in the query-string. Therefore, requesters can add multiple properties to the query-string for a new persister. In case the URI contains its own query-string, the URI separator, &URI=&, must be used to separate the original query-string and add-on properties. So please carefully define the add-on properties in the query-string of the URI. PersisterPool also allows the default properties defined for each implementation. If any of the default properties is missing in the URI, PersisterPool will copy it to the XML property map before the instantiation of the MessagePersister.

Apart from the common properties, there are many implementation specific properties for PersisterPool.

Property Name	Data Type	Requirement	Description	Examples
Heartbeat	integer	optional	interval in sec to check outstanding requests	30 (default: 60)
MaxNumberPersister	integer	optional	max number of persisters	32 (default: 256)
DefaultPoolSize	integer	optional	pool size for new persisters	8 (default: Capacity of the node)
Template	string	optional	template to build the URI
URIField	string	optional	field name for URI	(default: URI)
RCField	string	optional	field name to store return code (0 for success)	(default: ReturnCode)
DefaultProperty	list	optional	list of default property map for new persisters	see example

where DefaultProperty defines the default properties for all the supported persisters.

Here is an example of PersisterPool:

{
  "Name": "pstr_pool",
  "ClassName": "org.qbroker.persister.PersisterPool",
  "Operation": "accept",
  "LinkName": "pool",
  "Capacity": "256",
  "XAMode": "1",
  "MaxNumberPersister": "512",
  "DefaultPoolSize": "64",
  "Heartbeat": "60",
  "DisplayMask": "0",
  "StringProperty": {
    "URI": "pool"
  },
  "DefaultProperty": [{
    "ClassName": "org.qbroker.persister.StreamPersister",
    "URI": "tcp://localhost:7227",
    "Operation": "request",
    "EOTBytes": "0x0a",
    "KeepAlive": "true",
    "SOTimeout": "60000",
    "ReceiveTime": "1000",
    "PauseTime": "1000",
    "StandbyTime": "5000",
    "RetryTimeout": "300",
    "MaxIdleTime": "900",
    "Template": "##body## ~ ReturnCode ~ ##ReturnCode##\n",
    "Parser": {
      "ClassName": "org.qbroker.event.EventParser"
    },
    "PoolSize": "256",
    "DisplayMask": "0"
  },{
    "ClassName": "org.qbroker.persister.JMSPersister",
    "URI": "wmq://localhost",
    "QueueName": "YLU",
    "Operation": "put",
    "MaxIdleTime": "900",
    "PoolSize": "256",
    "DisplayMask": "0"
  },{
    "ClassName": "org.qbroker.persister.JMSPublisher",
    "URI": "wmq://localhost",
    "TopicName": "YLU",
    "Operation": "pub",
    "MaxIdleTime": "900",
    "PoolSize": "128",
    "DisplayMask": "0"
  },{
    "ClassName": "org.qbroker.persister.FilePersister",
    "URI": "http://localhost:8080/",
    "Operation": "download",
    "MaxIdleTime": "900",
    "PoolSize": "256",
    "DisplayMask": "0"
  }]
}