The retry design pattern is a pattern used to handle transient failures in a system. Transient failures are temporary errors that occur due to issues such as network congestion, timeouts, or temporary unavailability of a service. The retry pattern allows a system to automatically retry a failed operation a certain number of times, with a delay between each retry.
The retry pattern is useful for improving the reliability and availability of a system, by allowing it to automatically recover from transient failures. The pattern can be applied to a wide range of operations, such as database queries, API calls, or file operations.
The retry pattern includes the following steps:
- The system attempts to perform an operation.
- If the operation fails, the system waits for a specified delay before retrying the operation.
- If the operation continues to fail after a certain number of retries, the system can take an alternate action, such as logging an error or escalating the issue to a higher level.
There are various strategies for determining the number of retries, delay, and the type of failures that should be retried. Some common strategies include using a fixed number of retries, using an exponential backoff delay, or using a jitter strategy to add randomness to the delay.
Guide to implement the retry pattern
Here are some general steps that can be used to implement the retry pattern:
- Identify the operations that need to be retried: Identify the operations in your system that are prone to transient failures and that would benefit from the retry pattern.
- Determine the retry strategy: Decide on the number of retries, delay between retries, and the type of failures that should be retried. You can use a fixed number of retries, an exponential backoff delay, or a jitter strategy to add randomness to the delay.
- Implement the retry logic: Use a try-catch block or a similar mechanism to catch the exception when the operation fails. Within the catch block, implement the retry logic. This can include a loop that retries the operation a specified number of times, with a delay between each retry.
- Handle the final failure: After the specified number of retries have been attempted, the system should take an alternate action, such as logging an error or escalating the issue to a higher level.
- Monitor and improve: Monitor the system to see how often the retry pattern is being used, and how often it is successful. Use this information to improve the retry strategy and fine-tune the parameters (number of retries, delay, etc.).
- Consider the specific scenario: Consider the scenario and the specific use case when implementing the retry pattern. For example, when working with sensitive data or financial transactions, retry logic may not be the best approach.
Retry Pattern Libraries
You can use libraries like Polly (.NET / C#) Polly JS (JavaScript), Spring Retry (Java), or similar libraries to implement the retry pattern in your system. These libraries provide a convenient, easy-to-use interface for retry logic and often include built-in strategies for handling retries, delays, and other features.
Considerations
The retry pattern is not a silver bullet, it can improve the reliability of the system, but it’s not suitable for all types of failures, like permanent failure. It’s important to consider the specific use case and the characteristics of the system when deciding whether to use the retry pattern and how to implement it.
For more information, refer to the Retry pattern on the Microsoft website.