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The throttle widget in JBlitz Professional allows you to speed up or slow-down the rate at which requests are made to the server. It works by modifying the pause time between requests. Increased speed is achieved by reducing the configured pause time and decreased speed by increasing the configured pause time.  The throttle value can vary from -100 (slowest) through 0 (neutral) to +100 (full throttle). -100   Slowest speed. Results in an infinite pause time between requests (effectively pauses the entire test run). 0   Neutral throttle. The pause time as configured in your test cases applies. +100   Fastest speed. Results in zero pause time between requests.

Throttle control and active profile

The throttle widget is displayed at the bottom right of the main screen and shows a small blue 'lever' handle that can be clicked and dragged using the mouse or keyboard. When the lever is at the topmost position, the throttle is at +100 (fastest). When it is in the middle, it is at 0 (neutral) and when it is at the bottom position, it is at -100 (slowest).

There are two modes of operation for controlling the throttle:

1. Manual control. Simply click and drag the throttle lever whilst your test run is ongoing to speed it up or slow it down. When you move the lever, JBlitz will show you the changing throttle value just to the right. Also, you should be able to see the effect it has on the displayed pause times shown to the right of each web page icon in the 'Main Setup' tab.
2. Automatic control. You can have JBlitz control the throttle lever for you during your test runs. To do this, you need to setup a throttle profile which defines what value the throttle should assume at each point in time during the run. When automatic throttle control is enabled, you should see a small 'profile' icon in the bottom right corner of the throttle widget.

Manual and automatic throttle control are explained in more detail below. Whichever mode is in operation, JBlitz will be working with a defined throttle value at each point in time during the test run. This value works across all virtual users and all test cases. It is combined with the configured pause time for each web page in each test case to calculate an effective pause time for that web page. 

JBlitz gives you feedback how the throttle is working during your test runs in the following ways:

• The effective pause time is displayed to the right of each web page icon on the 'Main Setup' tab of the main screen. This figure is how long JBlitz is actually pausing given the momentary throttle value. Hover the mouse over the figure to see what throttle value is being used.
• The throttle widget displays a hover tooltip. Move the mouse over the widget to see a summary of throttle information including the current throttle value. 
• Throttle values can be optionally displayed in the graph windows. Click on the Show throttle check-box. The throttle value is shown as a thick black line with a throttle scale displayed to the right.
• If automatic throttle control is in use, the small 'profile' icon to the bottom right of the throttle widget displays its own hover tooltip. This shows the profile being followed and shows a flashing red circle marking where on the throttle profile JBlitz is currently positioned (see screen-shot above).

In addition to using the throttle widget to vary the load on your website or web application, remember that you can also stop and restart individual virtual users using the Virtual User Activity window. This is a handy way of additionally varying the simulated load.

Note: the evaluation version of JBlitz has an evaluation limit on the pause time between requests. This is 2000ms at neutral throttle and a minimum of 1000ms even at full throttle. Of course, the retail version has no such limitation - you can see what pause time would be applied, if you were using the retail version, displayed in brackets next to the web page icon.

The simplest means of controlling the throttle during a test run is to manually click and drag it. You can do this either before your test run begins (to set an initial value for the throttle) or whilst the test run is ongoing to speed it up or slow it down.

To modify the throttle value manually either:

• Click on the blue 'lever' handle and drag it upwards or downwards.
• Click just below or above the blue 'lever' handle. This adjusts the throttle in increments of 10.
• Click on the right mouse button and select 'Increase Throttle' or 'Decrease Throttle' from the popup menu.
• Click on the throttle widget (away from the lever) and press the up or down keys. This adjusts the throttle in increments of 10. Also, pressing page up or page down moves the throttle immediately to either full throttle (+100) or minimum throttle (-100).

Manual throttle control is the default setting for JBlitz. It is shown by the absence of any 'profile' icon on the throttle widget. In the manual throttle control mode, the throttle widget displays an appropriate tooltip explaining that no automatic throttle control is currently active.

Even when automatic throttle control is activated and a test run is ongoing, you can still assume manual throttle control by clicking and dragging the throttle lever. You will be prompted as to whether you would like to assume manual throttle control. Select 'Yes' to continue the test run using manual control, 'No' to keep using the active profile to control the throttle automatically.

JBlitz can automatically apply pre-configured throttle values during a test run by following a throttle 'profile'. Throttle profiles define the values to be used at each point in time. JBlitz simply follows the profile as the run proceeds and 'moves' the throttle lever for you according to the profile you have defined.

Throttle profiles: Define the throttle value to use for each second within the test run. Values are in the range -100 -> +100. Have a pre-defined duration. Profiles can be as short as 5 minutes and as long as 8 days. Can follow any arbitrary curve / set of lines. You can either 'draw' the profile yourself using the mouse or specify an equation to define it. Currently supported is linear, quadratic, sinusoidal, single step and double step. Wrap. When the end of a profile is reached, JBlitz follows the profile again from the beginning. Are stored as binary files on your hard-disk. The values in the file are converted into the range -100 -> +100, each byte defining the value for an individual second. Are organized into a profiles folder. JBlitz always looks for profiles in the profile storage folder.		A throttle profile

When a profile is used for automatic throttle control, it is said to be activated. The active profile is indicated by a small 'profile' icon in the bottom right corner of the throttle widget. Only one profile may be active at any point in time. If the active profile is deactivated, the profile icon will disappear (manual control is assumed).

All aspects of throttle profile creation and management can be performed using the Profile Manager as described below.

The Profile Manager gives you a view of all the profile files stored on your hard disk in the current profile storage folder. It also provides a central location for creating, deleting, activating, deactivating and editing each profile.

At the top of the window, a list of your profile files is shown. All files residing in the profile storage folder are shown. Buttons to the right give access to the main functions. The active profile, if any, is shown in bold with a green 'tick' mark against it. Double-clicking on any profile in the list brings up the profile editor.

Below the profile list, a preview of the currently selected profile is shown. The preview is not in itself editable, but you can double-click on it to bring up the profile editor.

Below the profile preview, the current profile storage folder is displayed. This is the location on your hard disk where JBlitz will expect to find your profiles. You can alter this location as required. You are advised to make the folder one where other (non-profile) information does not exist as JBlitz interprets every file found in this folder as a 'profile'.

The Profile Manager		To the right of the profiles list, a set of buttons give access to the main profile functions: Activate Makes the selected profile active. This profile will be used for automatic throttle control. You should see the small profile appear icon in the bottom right of the throttle widget on the main screen.   Deactivate If the selected profile is currently the active one, deactivates it to revert to manual throttle control.   Create Allows you to create a new throttle profile and brings up the profile editor. New profiles are given a default file name which you can modify to suit. See below for more information.   Edit Brings up the profile editor allowing you to edit the profile. See below.   Delete Removes the profile from your hard-disk, deleting it permanently. Be careful when you perform this operation as it cannot be undone.   Refresh Refreshes the profile list from disk. If you copy or create profile files manually (through Explorer or whatever), click 'Refresh' to have JBlitz synchronize with the changes to your hard-disk.

The profile editor provides creation / editing facilities for throttle profiles within JBlitz. A dialog is shown where you can specify the name for the profile file (full name including any file extension you want), the duration (this will depend on how long your test runs are anticipated to last) and the throttle values themselves.

The blue graph panel displayed centrally shows the throttle values to be used. The values are displayed in red. Choose a suitable editing mode for specifying the values by selecting one from the combo-box in the bottom left of the screen:

• Free draw. Click and drag the mouse on the graph panel to create the values. You can go over and over to repeat / amend portions of the graph.
• Line draw: Click and drag the mouse in a similar way to free draw, but JBlitz creates lines instead. Repeat as necessary until you have attained the correct shape.
• Equation: Select an equation type (e.g. linear) and click on the 'Equation' button to the right. You will be asked to input the coefficients for the equation. You can click 'Apply' to see what the result is and redo until you are happy. Then click 'Close'.

Remember, you can change the editing mode at any time and thus produce a profile that is produced with a combination of modes (the one shown above is a combination of free draw and line modes). Also, note that JBlitz will repeatedly cycle through the profile once it has reached the end (i.e. it wraps), so you don't necessarily have to make the profile duration encompass the whole duration of your test runs.

To bring up the profile editor:

1. Click 'Create' or 'Edit' from the Profile Manager.
2. Double-click on a profile displayed in the Profile Manager profiles list.
3. Double-click on a profile preview displayed in the Profile Manager.
4. Select 'Throttle Profiles->New Profile...' or 'Throttle Profiles->Edit Active Profile...' from the right mouse popup menu on the throttle widget at the bottom of the main screen.
5. Double-click on the small active profile icon displayed at the bottom right of the profile widget on the main screen. This only applies if an active profile exists.

To have JBlitz automatically control the throttle during test runs, an active throttle profile must be specified. The easiest way to do this is to bring up the Profile Manager window, select the profile to activate and click the 'Activate' button to the right.

Alternately, you can use the right mouse popup menu on the throttle widget and select the menu options 'Throttle Profiles->Select Active Profile'. The active profile, if any, is shown in the sub-menu with a tick mark against it.

When automatic throttle control is activated, and no test run is ongoing, you can deactivate the active profile using the Profile Manager window and clicking the 'Deactivate' button to the right. Alternately, you can use the right mouse popup menu on the throttle widget and select the menu options 'Throttle Profiles->Deactivate Active Profile'.

Whilst a test run is ongoing, clicking and dragging the throttle lever with the mouse will make JBlitz prompt you as to whether you want to revert to manual control. If you select 'Yes', JBlitz will deactivate the active profile for you and you may then click and drag the lever manually. Once you have reverted to manual control, you cannot re-activate the prior profile as long as the test run is ongoing.