Context and Problem
In high-traffic systems, excessive requests can overwhelm backend systems, resulting in slowdowns or failures.
- Traffic spikes causing system overload.
- Resource exhaustion due to too many simultaneous requests.
- Maintaining consistent service performance under varying load conditions.
Solution
Throttling controls the rate at which requests are processed to ensure that systems remain responsive even during periods of high demand.
- Define the acceptable rate of requests that can be processed (e.g., per second or per minute).
- Implement a throttling mechanism that temporarily blocks or delays requests that exceed the rate limit.
- Monitor traffic patterns to adjust throttling thresholds dynamically as needed.
- Inform clients when throttling occurs, either with an appropriate response code or message.
- Consider using backpressure to manage load, allowing clients to retry requests after some time.
Benefits
- System Protection
- Throttling helps protect the system from overload by limiting the number of requests that can be processed.
- Stability
- Helps ensure consistent performance even under high load by regulating the flow of requests.
- Fairness
- Ensures that all users have equal access to system resources by preventing abuse from high-frequency requests.
Trade-offs
- Increased Latency
- Throttling can cause delays in request processing when the rate limit is reached.
- Complexity
- Requires careful configuration and tuning to balance throttling thresholds with user needs.
- User Experience Impact
- Users may experience slower responses or delays when throttling is applied.
Issues and Considerations
- Threshold definition
- Determining the appropriate rate limit to balance system performance with user experience.
- Handling spikes
- Managing sudden traffic spikes effectively without degrading service quality.
- Communication with clients
- Ensuring clients are properly informed when their requests are throttled.
When to Use This Pattern
- When you need to protect backend services from excessive traffic.
- When you want to ensure consistent performance during traffic spikes.
- When system resources are limited, and you want to control how requests are processed.