| The *acknowledgement pattern* is a simple method of flow-control for methods |
| that would otherwise be one way calls. Rather than leaving the method as a one |
| way call, it is instead turned into the a two way call with an absent response, |
| colloquially known as an *ack*. The ack's only reason for existence is to inform |
| the sended that the message has been received, which the sender can use to make |
| decisions about how to proceed. |
| |
| The cost of this acknowledgement is added chatter over the channel. This pattern |
| can also result in degraded performance if the client waits for the |
| acknowledgement before proceeding with the next call. |
| |
| <<../examples/canvas/_callout.md>> |
| <<../examples/canvas/_add_line_metered_tutorial.md>> |
