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Sequencer component is used to retain the sequence of messages when a certain section of the flow has to be processed in multiple flows for performance concerns. When messages are split into parallel flows, the messages are not guaranteed to reach the end of the flow in the order of their arrival. A pair of sequencer components launched in Generate and Resequence modes respectively ensures the order is maintained.
Configuration
Custom configurations can be made in the Sequencer Configuration Property Sheet (CPS).
Figure 1: Sequencer Component Configuration properties
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Duration for which the message is retained in the component when the sequencer mode is 'Resequence'.
Figure 2: Resequence properties
Resequence Interval
Interval after which resequencing is attempted when the sequencer mode is 'Resequence'.
Initial Sequence Number
Number from which sequence starts. By default, it is set to 1.
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For the solution to work even when components are restarted, the following changes have to be made.
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Data
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Base Configuration
Click the ellipsis button to configure the required database.
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Refer the Database Configuration section in the DB page for descriptions of database configuration properties. |
Figure 23: Database Configuration
Expert Properties
Enable the Expert Properties view to configure these properties.
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Expert properties are meant for advanced users; use with caution. |
Figure 4: Expert properties for Generate sequencer mode
Pre Processing XSL Configuration
Pre Processing XSL configuration can be used to transform request message before processing it. Click the ellipses button against the property to configure the properties.
Refer to the Pre/Post Processing XSL Configuration section under the Common Configurations page for details regarding Pre Processing XSL configuration and Post Processing XSL configuration (below).
Post Processing XSL Configuration
Post Processing XSL configuration can be used to transform the response message before sending it to the output port.
Process Message Based on Property
The property helps components to skip certain messages from processing.
Refer to the Process Message Based On a Property section under the Common Configurations page.
Table Name
Name of the table to store the messages during execution.
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Default value is a combination of the event process name and the microservice name. |
Threadpool Configuration
This property is used when there is a need to process messages in parallel within the component, still maintaining the sequence from the external perspective.
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Click the Threadpool Configuration ellipsis button to configure the Threadpool Configuration properties.
Figure 35: Threadpool Configuration
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Time in milliseconds after which the threads are evicted in case of inactivity. New threads are created in place of evicted threads when new requests are received. Default value is '1000'.
Sequence Type
Figure 6: Expert properties for Resequence sequencer mode
The two sequence types for Resequence Sequencer Mode are:
- Continuous: Select this to have two consecutive sequence numbers differ by 1.
- Non-Continuous: Sequence numbers are not generated continuously.
Functional Demonstration
Scenario 1
The following figure demonstrates a skeleton use case of sequencing. The parallel flows are wrapped between the sequencer and resequencer components with the number of flows set in the configuration of both sequencer and resequencer.
Filters are appropriately set on routes so that each parallel flow receives the corresponding message.
Figure 47: Sample flow
Sample Output
Figure 58: Output in the Display window
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