Configuring the Sequence node
Configure the Sequence node to add a sequence number to one or more groups of input messages.
About this task
When you have put an instance of the Sequence node into a message flow, you can configure it; see Configuring a message flow node. The properties of the node are displayed in the Properties view. All mandatory properties that do not have a default value defined are marked with an asterisk.
To configure the Sequence node, set the following properties.
- Optional: On the Description tab, enter a Short description, a Long description, or both. You can also rename the node on this tab.
On the Basic tab, set the properties that determine how the message sequence is controlled.
- Use the Path to store sequence number property to specify the location in which to save the sequence number of the message. The location is specified as an XPath expression.
- Use the Path to sequence group identifier property to specify the location of the sequence group identifier. The location is specified as an XPath expression. Messages that have the same group identifier are considered part of the same sequence group.
- Use the Start of sequence definition property to specify the first sequence number in each group. In the Literal field, specify any positive or negative numeric value as the first sequence number in the group. The default value is 0.
When the first message of a specific sequence group is propagated by the Sequence node, the specified starting sequence number is used to assign the first sequence number; successive messages contain monotonically increasing sequence numbers. This value is overridden by the LocalEnvironment.Sequence.StartOfSequenceNumber variable.
- Use the End of sequence definition property to specify when each sequence group has been completed.
- Select Literal to specify a literal sequence number. This value can be any positive or negative numeric value that is greater than the value of the Start of sequence definition property. When the message with the specified sequence number arrives, the sequence group is closed.
- Select Predicate to specify an XPath expression that evaluates to either True or False, indicating whether the message is the last in the sequence. When the first message in the sequence has been determined, messages for that sequence group continue to have sequence numbers assigned to them until the end of sequence predicate evaluates to True.
If the XPath expression is valid but is not present in the message, it evaluates to False and the next message in the sequence group is assigned a sequence number. When the predicate evaluates to True, the message becomes the last in the sequence and no more messages are assigned to the sequence for that sequence group.
If the XPath expression is invalid, it fails and the message rolls back
- Select Automatic to specify the timeout period for the node. This option specifies how long (in seconds) the node waits for messages to arrive in an empty queue, before closing the sequence group. This option is useful for applications that cannot determine the final number in the sequence. The timer starts when there are no messages in the queue waiting to be propagated. If new messages arrive before the timeout period is reached, the timer is canceled. If no new messages arrive before the end of the specified time, the sequence group is closed and any further messages for the group are considered part of a new group.
- On the Advanced tab, use the Persistence mode property to specify whether to store sequence group state persistently. The default value is Non-persistent.