This topic explains how we built the Lock and Unlock operators sample.
This sample uses paired Lock and Unlock operators to protect shared data against concurrent writes. The sample is intended only to demonstrate how to protect the data, and does not include other concurrent operations which might access the data. Other concurrent operations could derive from data on different streams sharing the query table, or they could be generated by tuples on the same stream, which would have to wait for the tuple being protected by the Lock clearing the Unlock (presumably there would be additional operators between the Lock and Unlock to process the data.)
This example uses the same key for both the key into the Query Table and the key on which to lock for exclusive access.
In the Package Explorer, double-click to open the
LockUnlock.sbappapplication. Make sure the application is the currently active tab in the EventFlow Editor.
Click the Run button. This opens the SB Test/Debug perspective and starts the application.
In the Application Output view, select the
ReturnProtectedDataoutput 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.
In the Manual Input view, select the
Click Send Data, and observe this data appears in the Application Output view:
When done, press F9 or click the Stop Running Application button.
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.
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.
In window 1, type:
The window shows
notice[StreamBaseServer] listening on port 10000.
In window 2, type:
There is no output immediately, but the dequeuer is primed to display subsequent output of the application.
In window 3, type:
sbc enqueue WriteProtectedData
The sbc command is now awaiting keyboard input. Type:
In window 3, type: Ctrl+Z (Windows) or Ctrl+D (UNIX) to exit the sbc session.
Observe these lines in the dequeue window:
In window 3, type the following command to terminate the server and dequeuer:
In StreamBase Studio, import this sample with the following steps:
From the top menu, click→ .
Select operator from the Data Constructs and Operators category.
StreamBase Studio creates a single project for the operator samples.
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.
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:
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:
See Default Installation Directories for the default location of
studio-workspace on your system.