What happens in the half-open state for Anypoint MQ circuit breaker?

• A. After trip timeout, the Subscriber retrieves a single message to test; if the test succeeds, the system returns to Closed state.
• B. The system stops retrieving messages entirely.
• C. It permanently trips to Open.
• D. It ignores messages until externally signaled.

Answer: (A)

In this state, the circuit breaker performs a controlled, minimal test to check if the system has recovered. After the initial trip, once the timeout passes, the Half-Open phase lets the Subscriber retrieve a single test message to see if processing can proceed normally. If that test succeeds, it indicates stability and the system moves back to Normal operation (Closed). If the test fails, the breaker reopens and the timeout restarts to protect against another surge of failures.

This matches the idea of Half-Open as a cautious probe rather than continuous operation or a permanent halt. The other options describe behaviors that would either keep the system blocked, rigidly never recover, or require external signaling, which aren’t what Half-Open is designed to do.