The message service can generate and send regularly scheduled messages to message queues. You can subscribe to scheduled messages by installing a listener on a queue and subscribing to a topic that defines the times you want to be notified. In this example, we add a listener to “MyQueue” and subscribe to the topic “second:30”, which causes the message service to send a message to MyQueue at 30 seconds past each minute:
cms.addListener(“MyQueue”, “MyPackage/MyComp”); cms.addSelector(“MyQueue”, “topic = ‘<second:30>’”);
To request a message be sent to MyQueue at 15 and 45 minutes past each hour, use this syntax:
cms.addSelector("MyQueue", "topic = '<minute:15>'");
cms.addSelector("MyQueue", "topic = '<minute:45>'");
For information on how to add selectors using EAServer Manager, see Chapter 8, “Setting up the Message Service,” in the EAServer System Administration Guide.
Scheduled messages are delivered to queues with the appropriate selectors within milliseconds of the specified time. The time at which a component receives a message from the queue, however, depends on the number of unprocessed messages in the queue.
Scheduled message topic names can be either ‘<minute:NN>’ or ‘<second:NN>’. Additional constraints must include a variable name and value. You can use these variables to define the message topic subscriptions:
Variable |
Definition |
|---|---|
MINUTE |
Number of minutes past the hour |
SECOND |
Number of seconds past the minute |
HOUR_OF_DAY |
To specify 5 PM, “HOUR_OF_DAY = 17” |
HOUR |
Twice a day, at 6 AM and 6 PM, “HOUR = 6” |
YEAR |
Four-digit year, for example, 2000 |
MONTH |
The name of the month, for example, January, February, and so forth |
DATE |
Date of the month, 1-31 |
DAY_OF_MONTH |
Same as DATE |
DAY_OF_WEEK |
The name of the day of the week, for example, Monday, Tuesday, and so forth. |
DAY_OF_WEEK_IN_MONTH |
To specify the first Sunday in October, MONTH = October and DAY_OF_WEEK = Sunday and DAY_OF_WEEK_IN_MONTH = 1 |
DAY_OF_YEAR |
To specify February 1, “DAY_OF_YEAR = 32” |
WEEK_OF_MONTH |
The week number within the current month |
WEEK_OF_YEAR |
The week number within the current year |
The variable names are not case sensitive; minute and MINUTE are equivalent. You can find documentation for the variables, whose names correspond to the constants in the Java class java.util.Calendar, in the Java API Specification.
Scheduled messages are not saved to persistent storage and they are not replicated.
A scheduled message includes two properties that indicate the message creation time, which can be accessed by the component:
Property name |
Datatype |
Format |
|---|---|---|
@t |
double |
Number of milliseconds since 1 January 1970 |
ts |
string |
YYYY-MM-DD HH:MM:SS |
You can find the message structure definition in $JAGUAR/html/ir/CtsComponents.html.
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