Dealing with downstream service failures

A downstream payment service is failing repeatedly. Retries are piling on load and dragging the whole application down. The Circuit Breaker Simulator lets you see how a breaker protects the system in this exact scenario.

Try the following in the app:

• Click Make request (will fail) repeatedly. Watch the consecutive failure counter climb until the breaker trips to OPEN.
• While the breaker is OPEN, keep clicking Make request. Notice in the request log that calls are BLOCKED: they never reach the payment service.
• Wait for the 5-second cooldown to expire. The breaker moves to HALF_OPEN and allows one trial request.
• From HALF_OPEN, try Make successful request to close the breaker, or Make request (will fail) to trip it open again.

Once you have observed the behavior, you're ready to answer.

Question: While the breaker is OPEN, what happens to each request the application makes to the payment service?