Circuit Breaker

Definition

A circuit breaker watches calls to a dependency and, after repeated failures, opens: further calls are stopped immediately instead of attempted. After a pause it lets a few trial calls through and closes again only if they succeed, which protects both the caller and the struggling service.

In plain terms

The breaker has three states. Closed: calls go through and failures are counted. Open: calls are refused at once, without waiting for a timeout. Half-open: after a cool-down, a trial call is allowed; success closes the breaker, failure opens it again.

In data collection the same idea has a second meaning. If a source starts refusing or blocking requests, the right response is to stop, alert a person, and record the gap honestly, not to push harder or fill the gap with guesses. Stopping is the feature.

Example

Rule: open after 3 failures in a row, stay open for 10 minutes.

The collection log should show the 10:10–10:20 gap as missing data, not as zeros.

Common misunderstandings

• “The breaker fixes the failure.” It only limits the damage and gives the problem time to clear.
• “An open breaker is an error in the system.” It is the system working as designed.
• “It should always resume by itself.” When the cause is a block or a change in access conditions, a person should look before collection restarts.