How should I practice Circuit Breaker State Machine?

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Problem · Array

Circuit Breaker State Machine

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Problem statement

Simulate a circuit breaker over a finite sequence of request attempts. The breaker starts in CLOSED. Each row of requests is [timestamp, outcome], where timestamps are nondecreasing and outcome is SUCCESS or FAILURE.

In CLOSED, every request is allowed. A success resets the consecutive-failure count. A failure increments it. Reaching failureThreshold failures opens the breaker until timestamp + openDuration.
In OPEN, a request before the reopen time is rejected and its supplied outcome is ignored.
At or after the reopen time, the next request is the single HALF_OPEN probe. A successful probe closes and resets the breaker. A failed probe opens it again for another openDuration.

Rows with the same timestamp are processed in input order. Return one string per row: REJECTED:OPEN for a rejected request, or ALLOWED:<state-after-request> for an allowed request.

Function

runCircuitBreaker(requests: String[][], failureThreshold: int, openDuration: int) → String[]

Examples

Example 1

requests = [["0","SUCCESS"],["1","FAILURE"],["2","FAILURE"],["3","SUCCESS"],["7","SUCCESS"]]failureThreshold = 2openDuration = 4return = ["ALLOWED:CLOSED","ALLOWED:CLOSED","ALLOWED:OPEN","REJECTED:OPEN","ALLOWED:CLOSED"]

The failures at times 1 and 2 open the breaker until time 6. Time 3 is rejected, and the successful probe at time 7 closes it.

Example 2

requests = [["0","FAILURE"],["1","FAILURE"],["4","FAILURE"],["5","SUCCESS"],["7","SUCCESS"]]failureThreshold = 2openDuration = 3return = ["ALLOWED:CLOSED","ALLOWED:OPEN","ALLOWED:OPEN","REJECTED:OPEN","ALLOWED:CLOSED"]

The failed half-open probe at time 4 reopens the breaker until time 7. The time-5 row is rejected.

Constraints

1 <= requests.length <= 200000.
Every row has two strings: a nonnegative decimal timestamp and either SUCCESS or FAILURE.
Timestamps are nondecreasing and at most 10^18.
1 <= failureThreshold <= 10^9.
1 <= openDuration <= 2000000000.