Basic CircuitBreaker Node

CircuitBreaker.js

class CircuitBreaker {
  constructor(request) {
    this.request = request
    this.state = "CLOSED"
    this.failureThreshold = 3
    this.failureCount = 0
    this.successThreshold = 2
    this.successCount = 0
    this.timeout = 6000
    this.nextAttempt = Date.now()
  }

  async fire() {
    if (this.state === "OPEN") {
      if (this.nextAttempt <= Date.now()) {
        this.state = "HALF"
      } else {
        throw new Error("Breaker is OPEN")
      }
    }
    try {
      const response = await this.request()
      return this.success(response)
    } catch (err) {
      return this.fail(err)
    }
  }

  success(response) {
    if (this.state === "HALF") {
      this.successCount++
      if (this.successCount > this.successThreshold) {
        this.successCount = 0
        this.state = "CLOSED"
      }
    }
    this.failureCount = 0

    this.status("Success")
    return response
  }

  fail(err) {
    this.failureCount++
    if (this.failureCount >= this.failureThreshold) {
      this.state = "OPEN"
      this.nextAttempt = Date.now() + this.timeout
    }
    this.status("Failure")
    return err
  }

  status(action) {
    console.table({
      Action: action,
      Timestamp: Date.now(),
      Successes: this.successCount,
      Failures: this.failureCount,
      "Next State": this.state
    })
  }
}

module.exports = CircuitBreaker