Heartbeat Merge Sample

About This Guide

This sample uses two Heartbeat operators to prevent a Merge operator from starving when either of its inputs stop receiving tuples. Without the Heartbeat operators, the Merge operator would stop outputting tuples as soon as either of its two input streams is inactive, even if it continued to receive tuples on the other input stream.

This sample also demonstrates how to flag the non-heartbeat tuples on an input stream, so that the heartbeat tuples can be filtered out later on.

Importing This Sample into StreamBase Studio

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

  • From the top menu, click FileLoad StreamBase Sample.

  • Type operator to narrow the list of options.

  • Select Operator sample group from the Data Constructs and Operators category.

  • Click OK.

StreamBase Studio creates a single project for the operator samples.

Running HeartbeatMerge.sbapp in StreamBase Studio

  1. In the Project Explorer, open the sample you just loaded.

  2. Open the src/main/eventflow folder.

  3. Open the package folder (most samples contain a single package folder. Open the top-level package folder if your sample contains more than one folder).

  4. Open the HeartbeatMerge.sbapp application and click the Run button. This opens the SB Test/Debug perspective and starts the application.

    If you see red marks, wait a moment for the project in Studio to load its features.

    If red marks do not resolve themselves in a moment, select the project and right-click MavenUpdate Project from the context menu.

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

  6. In the Manual Input view, select the Feed1 input stream.

  7. Enter IBM for symbol, 83.17 for price, and 2005-11-02 12:00:00 for time.

  8. Click Send Data. You should not see any output in the Output View yet. The tuple you just sent is currently buffered in the Merge operator.

  9. Select the Feed2 input stream.

  10. Enter MSFT for symbol, 24.89 for price, and 2005-11-02 12:00:30 for time.

  11. Click Send Data. You should now see the IBM tuple in Output View.

  12. Wait a few moments. Within 30 seconds, look for the MSFT tuple to appear in the Output View. If this application had not made use of Heartbeat operators, the MSFT tuple would have remained inside the Merge operator until Feed1 received a tuple with a timestamp greater than or equal to 2005-11-02 12:00:30. Instead, the Heartbeat operators continually emit such tuples, thereby preventing the Merge operator from getting stuck. You can see this for yourself by selecting the Feed1WithHeartbeats output stream in the Output View.

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

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 default location of studio-workspace on your system.