Using the Split Operator

The Split operator splits its incoming stream into two or more outgoing streams that execute in a guaranteed specific order. Each incoming tuple is sent first to output port 1, then to output port 2, and so on.

By contrast, you can also split the path of execution by drawing multiple arcs from an operator's output ports, as shown in the following illustration.

However, in this case, the order in which tuples proceed out the multiple arcs is not known and is not guaranteed. By using a Split operator, you can obtain guaranteed processing order.

In the example above, an inbound tuple is first sent to the downstream components connected to the Split operator's Output port #1, the top port. After the processing of that tuple completes on the top path, an exact copy of the inbound tuple is sent out the Split operator's Output port #2 to the bottom path.

How does the Split operator know that a tuple has completed processing along the top path before sending the same tuple out the bottom path? The Split operator does not track the processing undergone by a tuple after it leaves its output ports, and it does not wait for a return value in any way. The processing sequence is guaranteed because, when StreamBase Server compiles the EventFlow application into executable code, it does so in the order in which components are organized in the canvas, and in the order of output port numbers of the Split operator.

The diagram above has red numbers to indicate the processing order of each component. When the server runs this compiled application, it encounters steps 2 and 6 in the Split operator. The server executes in the order 2, 3, 4, and 5 before returning to step 6 and beyond.

Name: Every application component must have a unique name. Use this field to specify or change the component's name. The name must contain only alphabetic characters, numbers, and underscores, and no hyphens or other special characters. The first character must be alphabetic or an underscore.

Enable Error Output Port: Check this box to add an Error Port to this component. In the EventFlow canvas, the Error Port shows as a red output port, always the last port for the component. See Using Error Ports and Error Streams to learn about Error Ports.

Description: Optionally, enter a description to briefly describe the component's purpose and function. In the EventFlow canvas, you can see the description by pressing Ctrl while the component's tooltip is displayed.

Use the Split Settings tab to specify the number of output ports, which correspond to the number of downstream paths that will receive a copy of the tuple in sequence, as in output port number order. Once the output ports are set up, you can then draw an arc from the Split operator's Output port #1 (top port) to the intended downstream path that should receive the tuple first. Then connect the Split operator's Output port #2 to the downstream path that should receive the same tuple second, after the first copy of the tuple was processed to completion. As needed, continue making the connections (in sequence) for each output port and the intended downstream path.

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