Presto Administration : Event Service Configuration and Administration : Manage Apama Event Sources : Edit Apama Event Sources
Edit Apama Event Sources
You can edit an already existing Apama Event Source.
To edite an Apama Event Source:
1. Click Admin Console in the Presto Hub main menu.
2. Click Event Service to expand this section of the Administration menu.
3. Click Event Service. The Event Service page will be displayed.
4. Open the Apama tab.
5. Click the Edit icon to configure an Apama Event Source.
6. Set the properties for this event source. See table Apama Event Source properties below.
7. Click Save.
The Apama Event Source is created and listed by alias name.
Table 9. Apama Event Source properties
Property
Required
Description
Alias
yes
Enter a unique name for this event source.
Start event source automatically on server startup
This option is set by default, which automatically starts this event source when Presto Server starts. Clear this option if you need to manually control startup for this event source.
Apama URL
yes
URL to the running Apama system ( local or remote)
Apama Scenario
yes
Click Refresh to update the list of Apama scenarios for the selected Apama Event Source. If the Apama URL is set to a valid Apama system, then it is possible to select a scenario this event source should subscribe to.
Strategy
yes
The strategy that this event source uses for saving and removing events published from the Event Bus. Valid strategies are:
*BUFFER = FIFO (first in-first out). Events are stored until event source memory reaches capacity and then the event source removes the oldest events.
*DELTA= Events are stored by ID and added, updated or removed based on a command within the event. An event with an Insert command is saved in event source memory, any existing event with the same ID is overwritten. An event with a Remove command removes an existing event with the same ID.
*PARTIAL_EVENTS = Each event has a unique identifier defined by one or more key fields (see Key attributes). Events contain additional fields, but may not contain all fields possible for the event. Simply put, each event may contain partial data.
The event source maintains a single row for each unique event key representing the current full status for that event. Events published by Apama scenarios update the fields in that event source row that are included in the event, leaving other existing data for that event source row intact.
Events that have a new unique key are saved as a new row until event source memory is full. Once the event source memory is full, new events are discarded.
Consider dimension
Available only when Strategy is set to BUFFER.
Set this option to save events in separate series (or buckets) for each unique value of the Dimension attribute.
Dimension attribute
conditional
Available only when Strategy is set to BUFFER and required when the Consider dimension option is set.
Select the event attribute whose unique values determine separate event series (buckets) for this event source.
Max. number of dimension values
conditional
Available only when Strategy is set to BUFFER and required when the Consider dimension option is set.
Enter the maximum number of unique dimension values (buckets) that can be tracked. Thus this is the maximum number of series that can store events.
Default value: 10 (Max: 100.000).
The product of Max. number of dimension values and Capacity per dimension value must not be greater than 100.000.
Dimension Squeeze-out
Available only when Strategy is set to BUFFER and required when the Consider dimension option is set.
Determines how additional events are handled if they have new unique values for the dimension that defines buckets in this event source but the maximum number of unique values (buckets) has already been reached.
This option is clear by default which discards new events with new unique dimension values once the maximum number of buckets has been reached.
Set this option to change the bucket strategy to FIFO (first-in, first-out) which discards events for older series (buckets) and stores the newer event in a new series (bucket).
Default value: false
Capacity per dimension value
conditional
Available only when Strategy is set to BUFFER and required when the Consider dimension option is set.
Enter the maximum number of events that can be stored in a specific event series (bucket) for each unique dimension value.
Default value: 10;
The product from Max number of dimension values and Capacity per dimension value must not be more than 100 000.
Event ID attribute
yes
Available only when Strategy is set to DELTA.
Select the attribute that identifies an event. The event ID and command determines which events are stored, updated or removed in this event source.
Command attribute
yes
Available only when Strategy if set to DELTA.
Select the attribute that contains the event command (Insert or Remove). The event ID and command determines which events are stored, updated or removed in this event source.
Key attributes
yes
Available only when Strategy is set to PARTIAL_EVENT.
The field(s) in events with partial data that uniquely identify an event. The event ID is used to ensure that events with partial data properly insert or update events in this event source.
Select one or more attributes that uniquely identify events for this Apama scenario. If multiple fields are required, the order in which you select attributes determines how fields are combined to determine event IDs.
Capacity
yes
Enter the maximum number of events to store in this event source. (Max: 100.000)
Default value: 10
Memory model
Determines where events are stored:
*Internal: the default which stores events in local memory for this event source.
*BigMemory: stores events in a local BigMemory cache.
Throttling
Controls the speed and volume of event data that is pushed to views that subscribe to this event source. By default, event sources push event data every 500 milliseconds. You can:
*Change the number of milliseconds to control throttling.
*Change the measurement (Default=500) to Events to have throttling wait until a specific number of events are received and change the number, if needed.
Exception
Set this option to support a hybrid throttling strategy, typically involving both time and event limitations. Then set the exception criteria (Default=1):
*A number
*Milliseconds or Events as the measurement for the exception criteria
Simple and Hybrid Throttling Strategies
Simple throttling strategies cause an event source to wait for either a specific time interval or for the receipt of a specific number of events and then push all new events to any subscribing real-time views. Throttling can slow event updates to real-time views when the volume or frequency for events causes rendering issues.
The default behavior is to push events to views based on a time interval of every 500 milliseconds. You can change the time interval or change the criteria to push events once a minimum count of events are received, such as 10 events. For example:
Simple strategies may still not even out event flow adequately. Instead, you can create hybrid strategies, such as "generally push every 50 milliseconds, but at most 10 events."
Hybrid strategies define the general throttling with the Throttling fields. You set the Exception option and define the exception that should break the general rule in the Exception criteria fields:
With the example hybrid throttling strategy shown above:
*The event source would wait 50 milliseconds after pushing events to subscribing views.
*If less than 10 events are received in that 50 milliseconds, they are pushed at the end of the interval.
*If a tenth event is received within the 50 milliseconds, these 10 events are pushed to subscribing views and both the time interval and the count of events begins again.
*If no events are received within the time interval, the event source waits until it receives an event. When an event is received, the event source pushes this event to subscribing views and restarts the time interval.
On the Apama Event Source overview page you can click on the Alias to show a preview of the specific Event Source propereties.
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