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What is a Notifier?

Updated Jun 26, 2019

Reported In


  • LabVIEW

Issue Details

What is a notifier and how do I use it in LabVIEW?


Notifiers are a tool for communicating between two independent parts of a block diagram or between two or more VIs running on the same machine. Notifiers cannot communicate across networks or the VI Server. This communication is generally for the purpose of synchronizing two independent processes.
Figure 1: The VIs on the Notifier Palette (Programming » Synchronization » Notifier Operations)
Notifiers are similar to mailboxes for data: one process sends data to the mailbox and one or several other processes receive data from the mailbox. In this way, they are similar to local or global variables. When using a variable, however, a process that is waiting for information must cycle continuously to check the value of the variable. One benefit of notifiers is that a process that receives information completely stops execution while waiting, and starts only when new data becomes available. This reduces excess processing power being wasted on unneeded polling.

Unlike Queue Operations functions, Notifier Operations functions do not buffer sent messages. If no nodes are waiting on a message when it is sent, the data is lost if another message is sent. Notifiers behave like single-element, bounded, loss-y queues.

Additional Information

Look for example programs in the LabVIEW shipping examples. Open LabVIEW » Help » Find Examples. Search for notifier on the Search Tab.