Which Design Patterns Exist for Asynchronous Promise Retries?

Designing Patterns for Promise Retries

In asynchronous programming, it's often useful to retry failed promises until they resolve. Here are three design patterns for achieving this with Promises:

1. Retry Until Promise Resolves (with Delay and Max Retries)

This pattern allows you to retry a promise until it resolves successfully, with a delay between each retry. It uses a for loop to create a chain of .catch() handlers, followed by a .then() handler for the successful resolution.

<code class="javascript">var max = 5;
var p = Promise.reject();

for(var i=0; i<max; i++) {
    p = p.catch(attempt).catch(rejectDelay);
}
p = p.then(processResult).catch(errorHandler);</code>

2. Retry Until Condition Meets on Result (without Delay)

This pattern allows you to retry a promise until a specific condition is met on the result. It uses a similar .catch() chain approach as the previous pattern, but instead of a rejectDelay, it uses a .then() handler to test the result.

<code class="javascript">var max = 5;
var p = Promise.reject();

for(var i=0; i<max; i++) {
    p = p.catch(attempt).then(test);
}
p = p.then(processResult).catch(errorHandler);</code>

3. Retry Until Condition Meets on Result (with Delay)

This pattern combines the previous two patterns, allowing you to retry a promise until a condition is met, with a delay between each retry. It uses a .catch() chain to handle retries and a .then() handler to perform the test and introduce the delay.

<code class="javascript">var max = 5;
var p = Promise.reject();

for(var i=0; i<max; i++) {
    p = p.catch(attempt).then(test).catch(rejectDelay);
}
p = p.then(processResult).catch(errorHandler);</code>

These patterns provide a concise and efficient way to handle retries with Promises, ensuring that your code continues to execute even when failures occur. They can be customized to meet the specific needs of your application, balancing factors such as maximum retries, delay intervals, and retry conditions.

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