Durable Details Panel
The Durable details panel presents the parameters of a static durable or a dynamic durable template. In edit mode, you can modify the parameter values.
The title of the panel indicates the location and name of the durable or template: Store / Durable.
For consequences of modifying this configuration, see Store and Durable Modifications.
For background information, see Durable Behavior.
| GUI Parameter | Description |
|---|---|
| Prefetch Count |
When a subscriber is ready, the store delivers a portion of the message stream. This value, a positive integer, limits the number of messages in a portion. Zero is a special value that disables prefetch. For more information about selecting an appropriate value, see Durable Prefetch Count. It is illegal to enable or disable prefetch after a durable configuration has been deployed to the FTL server. (Nonetheless, you may still change the prefetch value from one positive integer to another positive integer.) |
| Message Limit | Optional.
This parameter limits persistence service memory growth by limiting the number of messages in a durable. When a message arrives, the persistence service checks the number of messages in the durable. If the new message would exceed the limit, the service discards a message (see the discard parameter). (When a durable discards the newest message, the publisher does not throw an exception. ) You can set this parameter for static durables and for dynamic durable templates. If you change its value on a dynamic durable template, all of that template's individual dynamic durables reflect the new behavior. This parameter does not apply to last-value durables. For further details, see Persistence Limits. |
| Discard | Optional.
This parameter governs the message discard behavior of the message limit parameter. The durable can discard either its oldest message or the new message. You can set this parameter for static durables and for dynamic durable templates. If you change its value on a dynamic durable template, all of that template's individual dynamic durables reflect the new behavior. This parameter does not apply to last-value durables. When absent, the default value is new. |
| Message Time to Live | Optional.
This parameter limits persistence service memory growth by limiting the time (in seconds) that messages remain in the durable. When a message arrives in the durable, a timer counts this interval. The persistence service can delete that message at any time after the interval elapses. Zero is a special value, indicating no time limit on messages in this durable. When absent, the default value is zero. For further details, see Persistence Limits. |
| Durable Time to Live | Optional.
This parameter limits persistence service memory growth by limiting the time (in seconds) that a dynamic durable without any subscribers can remain in the store. When a dynamic durable no longer has any connected subscribers, a timer counts this interval. The persistence service can delete the durable at any time after the interval elapses. During the interval, the presence of any subscriber stops the timer and prevents deletion.
Zero is a special value, indicating no time limit on dynamic durables without subscribers. When absent, the default value is zero. For further details, see Persistence Limits. |
| Batch Count | In asynchronous acknowledgment mode, each client immediately sends accumulated acknowledgements when the number of waiting acknowledgements exceeds this number, even if the batch time interval has not elapsed. |
| Batch Time | In asynchronous acknowledgment mode, each client immediately sends accumulated acknowledgements when the oldest acknowledgment has waited for this interval, in seconds, even before exceeding the batch count. |
| Maximum Delivery Attempts | Applies only to
shared durables.
This parameter limits the number of times that a persistence service will attempt to deliver each message in the shared durable. Zero is a special value, indicating no limit on delivery attempts. Administrators can this set parameter to zero or any positive integer strictly greater than one. (The value 1 is invalid.) When absent, the default value is zero. Note: Robust message callback methods verify field data types before operating on field data content.
Nonetheless, sometimes a message with unexpected data content can cause a subscribing application to abruptly exit. When the persistence service repeatedly delivers such a message to the subscribers of a shared durable, it could potentially cause all the subscribing applications to exit. To limit the damage that such messages can cause, set this parameter to a non-zero value that is less than the expected number of subscribing applications. |