Gather Operator Sample

The Gather.sbapp sample application has two EventFlow modules. The SimpleGather example uses a Gather operator to generate an alarm (a true value) for trades of 10,000 shares or more for a stock whose price is $200 or greater. The input stream contains the fields Symbol, Volume, and Price.

Note

This is a very simple example which might be better done using a single Map operator, but it is instructive. For an example that truly requires a Gather operator, see the Compliance sample application.

The TimeoutGather example demonstrates the effect of the Optional Timeouts settings. In this case, when no input is received for ten seconds, Gather is forced to emit whatever tuple values it has accumulated, setting any fields not received to null. The input stream has two string fields: Type (which must be enqueued as either Buy or Sell) and Symbol (which can be any string).

Running Gather.sbapp in StreamBase Studio

To run the SimpleGather example:

  1. In the Package Explorer, double-click to open the Gather.sbapp application. Make sure the application is the currently active tab in the EventFlow Editor.

  2. Click the Run button. This opens the SB Test/Debug perspective and starts the application.

  3. In the Application Output view, select the BigTradeAlarm output stream. No output is displayed at this point, but the dequeuer is prepared to receive output. This view will eventually show the output of the application.

  4. In the Manual Input view, select the TradesIn input stream.

  5. Enter intc, 10000, and 201 in the Symbol, Volume, and Price fields, respectively

  6. Click Send Data, and observe this data appears in the BigTradeAlarm stream:

    BigTradeAlarm=true
  7. Enter intc, 10000, and 199 in the Symbol, Volume, and Price fields, respectively

  8. Click Send Data, and observe this data appears in the BigTradeAlarm stream:

    BigTradeAlarm=false
  9. Enter intc, 1000, and 201 in the Symbol, Volume, and Price fields, respectively

  10. Click Send Data, and observe this data appears in the BigTradeAlarm stream:

    BigTradeAlarm=false
  11. Enter intc, 1000, and 187 in the Symbol, Volume, and Price fields, respectively

  12. Click Send Data, and observe this data appears in the BigTradeAlarm stream:

    BigTradeAlarm=false

To run the TimeoutGather example:

  1. In the Package Explorer, double-click to open the Gather.sbapp application. Make sure the application is the currently active tab in the EventFlow Editor.

  2. Click the Run button. This opens the SB Test/Debug perspective and starts the application.

  3. In the Application Output view, select the Matches output stream. No output is displayed at this point, but the dequeuer is prepared to receive output. This view will eventually show the output of the application.

  4. In the Manual Input view, select the SimpleBuySellMatch input stream.

  5. Enter Buy and intc in the Type and Symbol fields, respectively, and press Send Data.

  6. Quickly change Type from Buy to Sell and press Send Data again.

  7. Observe this data appear in the Matches stream:

    MatchedSymbol=intc
  8. Now change Type from Sell back to Buy again, and press Send Data.

  9. Do not send a Sell message. After 10 seconds, observe that the Gather operator times out, and writes the following to the Matches output stream:

    MatchedSymbol=<No Match: intc,null>

When done, press F9 or click the Stop Running Application button.

Running Gather.sbapp in Terminal Windows

This section describes how to run the sample in UNIX terminal windows or Windows command prompt windows. On Windows, be sure to use the StreamBase Command Prompt from the Start menu as described in the Test/Debug Guide, not the default command prompt.

To run the SimpleGather example:

  1. Open three terminal windows on UNIX, or three StreamBase Command Prompts on Windows. In each window, navigate to the directory where the sample is installed, or to your workspace copy of the sample, as described above.

  2. In window 1, type:

    sbd Gather.sbapp

    The window shows notice[StreamBaseServer] listening on port 10000.

  3. In window 2: type:

    sbc dequeue BigTradeAlarm

    No output is displayed at this point, but the dequeuer is prepared to receive output. This window will eventually show the output of the application.

  4. In window 3, type:

    sbc enqueue TradesIn

    The sbc command is now awaiting keyboard input. Then type: intc, 10000, 201

    Observe this line in the dequeue window: true

  5. Type:

    intc, 10000, 199.

    Observe this line in the dequeue window: false

  6. Type:

    intc, 1000, 201.

    Observe this line in the dequeue window: false

  7. Type:

    intc, 1000, 187.

    Observe this line in the dequeue window: false

  8. In window 3, type: Ctrl+Z (Windows) or Ctrl+D (UNIX) to exit the sbc session.

  9. In window 3, type the following command to terminate the server and dequeuer:

    sbadmin shutdown

To run the TimeoutGather example:

  1. Open three terminal windows on UNIX, or three StreamBase Command Prompts on Windows. In each window, navigate to the directory where the sample is installed, or to your workspace copy of the sample, as described above.

  2. In window 1, type:

    sbd Gather.sbapp

    The window shows notice[StreamBaseServer] listening on port 10000.

  3. In window 2: type:

    sbc dequeue Matches

    No output is displayed at this point, but the dequeuer is prepared to receive output. This window will eventually show the output of the application.

  4. In window 3, type:

    sbc enqueue SimpleBuySellMatch

    The sbc command is now awaiting keyboard input. Then type: Buy, intc

  5. Still in window 3, quickly type:

    Sell, intc

    Observe this line in the dequeue window: intc

  6. In window 3, now type:

    Buy, intc

    Stop typing now and wait until the dequeue window displays: <No Match: intc,null>

    The application's Gather operator reports any unmatched tuples due to its timeout setting, which in this example is set to 10 seconds.

  7. In window 3, type: Ctrl+Z (Windows) or Ctrl+D (UNIX) to exit the sbc session.

  8. In window 3, type the following command to terminate the server and dequeuer:

    sbadmin shutdown

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Importing This Sample into StreamBase Studio

In StreamBase Studio, import this sample with the following steps:

  • From the top menu, click FileLoad StreamBase Sample.

  • Select operator from the Data Constructs and Operators category.

  • Click OK.

StreamBase Studio creates a single project for all the operator samples.

Sample Location

When you load the sample into StreamBase Studio, Studio copies the sample project's files to your Studio workspace, which is normally part of your home directory, with full access rights.

Important

Load this sample in StreamBase Studio, and thereafter use the Studio workspace copy of the sample to run and test it, even when running from the command prompt.

Using the workspace copy of the sample avoids permission problems. The default workspace location for this sample is:

studio-workspace/sample_operator

See Default Installation Directories for the location of studio-workspace on your system.

In the default TIBCO StreamBase installation, this sample's files are initially installed in:

streambase-install-dir/sample/operator

See Default Installation Directories for the default location of studio-workspace on your system.