Developing Solutions for Microsoft Azure (AZ-204) Practice Exam

Which durable pattern allows a function to periodically check a condition until it is satisfied?

1. Function chaining

2. Fan out/fan in

3. Monitor

4. Request/response

The correct answer is: Monitor

The durable pattern that allows a function to periodically check a condition until it is satisfied is the Monitor pattern. This pattern is particularly useful in scenarios where you need to wait for an external condition to change — for instance, waiting for a file to appear in a storage account, or until an external system reaches a particular state. In the Monitor pattern, the function can run on a timer to check the condition at specified intervals. If the condition is not met, the function will delay its next check and continue polling until the desired state is achieved. This polling mechanism effectively manages long-running operations and provides a way to pause and resume execution based on external events. Other patterns, such as Function chaining, involve passing the output of one function directly to the next without the need for periodic checks. Fan out/fan in focuses on parallel processing of multiple functions to increase throughput. The Request/response pattern deals with synchronous operations where the response is expected immediately after making a request. Each of these patterns serves a unique purpose, but they do not specifically cater to the requirement of periodically checking a condition.