Below is a list of questions to ask to ensure an event is fully implemented with all available and relevant features.
Refer to Create Events for general information.
NOTE: When creating an event, a key column property must be set if the page is based on a view or if the page doesn’t have a primary key. For example, a user creates a background event that runs on a Vertical View, but the parameter, the primary key, only displays on the Horizontal View.
The user must either:
- Include the primary key as one of the arguments in the stored procedure (since it should be in both the Horizontal and Vertical View) and then, in the stored procedure, run a select statement to get another column's value from the Vertical View using the primary key.
- Include the column in the Horizontal View and hide it via a column property with the Horizontal View type. Refer to Set Column Control Status for more information.
NOTE: The options below are set on the Page Events page (Admin > WebApps> Pages > Events).
- Is this a large or long-running process best suited for the background? Does it need user-session-level context?Any event running for more than several seconds must be run in the background. If the process takes fewer than several seconds to run, or if the process needs user-session-level context, set it to run in the foreground. A Foreground event runs on the Web Server, which can give plugin code access to specific users and runtime information from the web session. A Foreground event can also provide immediate feedback to the user, such as reloading the page and displaying post-event messages. Configure this option using the EVENT PROCESS TYPE ID list box on the Page Events page.
- Should the user be warned before executing the event? If so, include a Pre Message, which prompts the user with an OK or Cancel option for continuing the execution of the event. Most actions that are not easily reversible should include a Pre Message to ensure the user does not accidently disrupt a process when executing an event. Enter the message in the Pre Message field on the Page Events page’s Vertical View.
- Should a Post Message be included? Post Messages display at different times depending on whether the event is foreground or background. A Background event displays the message as a Minor Notification immediately after the job has been queued. In this case, it is a good idea to use the Post Message to indicate to the user that the work will be run at a certain time (for example, “The package will be processed shortly.”). Foreground events display their message after execution. Post Messages for Foreground events are useful when executing plugin code that does not always write out a message, or when executing non-plugin Business rules. The Post Message ensures that the user always receives a confirmation that their action has completed. Enter the Post Message in the Post Message field on the Page Events page’s Vertical View.
- Should the Transaction Method be changed from the default (Disabled)? The options are:
- Disabled Transaction Method – Business rules stop running on exception. This option provides the least likeliness of a deadlock as well as fastest execution time. However, when running a series of procedures, an error in one will not result in a rollback of the previous procedures. This could potentially leave the database in an unstable state, if these procedures are not idempotent.
Enabled Transaction Method – Encapsulates the Business rules in a database transaction. This option provides the functionality of rolling back in the event of an error. This rollback is applied per Execution Groups, which are formed by sequential sets of stored procedures. For example:
- Three stored procedures run.
- An External Page runs.
- Three more procedures run.
This results in two Execution Groups (first three, and last three). In the event a procedure within one of the Execution Groups fails, any other procedure that has been run within that group is undone. This setting carries the highest potential of deadlock. A failure within an Execution Group does not cause any other execution groups to roll back.
Serialized Transaction Method – Only allows one instance of the page’s event to run at a time. For example, if User A and User B are attempting to execute the event (even against different records), one event has to complete before the other one starts.This option is similar to Enabled, with the added locking at the Page Event level. When this option is chosen, each event invocation will ensure exclusive execution of the underling Page Events rules. This option reduces the number of procedure related deadlocks occurring, but can lead to event lock related timeouts if several users are attempting to execute the same event simultaneously.
NOTE: This option must not be used if the column property supports multi-row actioning.
Set the Transaction Method on the Page Events page’s Vertical View on the Advanced Properties tab.
- At what “Event Level” should this event execute?The default and most commonly used Event Level is Row, which passes the row information to the event. The Page Event Level is commonly used for toolbar buttons defined from the Toolbar view for the page. The Page Event Level does not pass row-level information to the event. If a toolbar button is set to a Page-level event, the user can click the button to run the event when there are no records on the page. Set the Event Level on the Page Events page’s Vertical View on the Advanced Properties tab.
- Should a post event “Function” be utilized? This modifier allows the page designer to force the user either to be navigated back to their previous page or to the page’s Vertical View. For example, if the page designer selects Back, the user may be expected to navigate to a second page, click a particular button, and then be sent back to the previous page where that event has affected the previous record. The Vertical option can be used when an action on the Horizontal View requires that the user access the Vertical View, where additional information or required fields for a record display. Set the Function on the Page Events page’s Vertical View on the Advanced Properties tab.