Context and Problem
In distributed systems or microservices, operations often fail temporarily due to transient issues like network glitches or resource contention.
- Temporary failures that could be resolved with a retry.
- Increased system instability due to frequent retries without proper control.
- Difficulty in determining when to stop retrying to prevent resource waste.
- Increased latency and overhead from continuous retries.
Solution
The Retry pattern automatically retries failed operations with specific control mechanisms to improve the chances of success on transient failures.
- Detect failures in operations (e.g., timeouts, network errors).
- Implement retry logic with a defined number of retries and backoff intervals (e.g., exponential backoff).
- Optionally, implement a circuit breaker pattern to stop retries after a threshold.
- Ensure idempotency of operations, so retries do not cause undesirable side effects.
- Log failed attempts and monitor the success rate to fine-tune retry parameters.
Benefits
- Increased reliability
- Temporary issues are handled without causing system failure.
- Improved fault tolerance
- Allows the system to recover from transient errors without human intervention.
- Reduced downtime
- Reduces the chances of failing operations by automatically retrying them.
Trade-offs
- Increased latency
- Retrying operations introduces delays, especially when using backoff strategies.
- Resource consumption
- Retries consume additional system resources (e.g., CPU, memory, network bandwidth).
- Risk of repeated failures
- If the issue is not transient, retries may continue to fail and waste resources.
Issues and Considerations
- Backoff strategy
- Implementing an effective backoff strategy to prevent excessive retries.
- Circuit breaking
- Using a circuit breaker to stop retries after a certain number of failures.
- Idempotency
- Ensuring retries don’t cause unwanted side effects.
When to Use This Pattern
- When you expect transient failures due to temporary network or system issues.
- When retries are likely to succeed after a short time delay.
- When a task can be retried safely without risking data inconsistency or duplication.
- When you need to minimize the impact of temporary failures on the user experience.