Circuit Opened on first attempt and executing action after threshold is reached

[sesteva]

Thank you for creating this module. It is just what I was looking for.

Node.js Version:
v11.6.0
Operating System:
Darwin C02WG1E2HTDD 17.5.0 Darwin Kernel Version 17.5.0: Fri Apr 13 19:32:32 PDT 2018; root:xnu-4570.51.2~1/RELEASE_X86_64 x86_64

Steps to Produce Error:

I'm observing two behaviours that I suspect are defects:

1- When the first request is made - which takes more than the accepted timeout - the circuit becomes opened right away. My expectation was that it would track 3 failures - per options - and only then open the circuit

2- After 3 failed attempts, if I issue a new HTTP request, this is actually executed. My expectation was that it would NOT do it and fail fast.

My code and logs below...

async function fetchBookings() {
  const res = await axios.get("http://localhost:4000/api/v1/bookings");
  return {
    bookings: res.data
  };
}

function fallBack() {
  console.log("fallback");
  return {};
}

async function getData() {
  const options = {
    timeout: 500, 
    errorThresholdPercentage: 50, 
    resetTimeout: 30000, 
    maxFailures: 3
  };

  const breaker = circuitBreaker(fetchBookings, options);
  breaker.fallback(fallBack); // runs on every failure

  breaker.on("success", () => console.log("success"));
  breaker.on("failure", () => console.log("failed"));
  breaker.on("timeout", () => console.log("timed out"));
  breaker.on("reject", () => console.log("rejected"));
  breaker.on("open", () => console.log("opened"));
  breaker.on("halfOpen", () => console.log("halfOpened"));
  breaker.on("close", () => console.log("closed"));

  return breaker.fire().catch(console.error);
};

Logs

-- the First Request is made --
timed out
failed
opened
fallback
-- the Second Request is made --
timed out
failed
opened
fallback
-- the Third Request is made --
timed out
failed
opened
fallback
-- the Fourth Request is made --
timed out
failed
opened
fallback
-- after 30 seconds --
halfOpened
halfOpened

[lance]

Hi @sesteva thanks for your report. I haven't really dug into it yet, or reproduced it locally (I've been on vacation the last week :). But at first glance, I notice that you are using both maxFailures AND errorThresholdPercentage. These are meant to be (though not documented as) mutually exclusive. The maxFailures option is currently deprecated, and will likely be removed in the next major version release. I wonder if having both of these set is the cause of the admittedly strange behavior you are seeing. Can you try to remove either maxFailures or errorThresholdPercentage from the options and see how that affects your test case?

[lance]

@sesteva just checking in on this. Have you had an opportunity to test my theory above?

[lance]

@sesteva I am going to close this. I have confirmed that you just need to remove maxFailures. I also recommend creating the circuit outside of getData(), otherwise a new one is created every time you call the function.

I modified your code to look like this for my testing:

const circuitBreaker = require('.');

const options = {
  timeout: 500,
  errorThresholdPercentage: 50,
  resetTimeout: 30000
};

const breaker = circuitBreaker(fetchBookings, options);
breaker.fallback(fallBack); // runs on every failure

breaker.on('success', () => console.log('success'));
breaker.on('failure', e => console.log('failed', e));
breaker.on('timeout', e => console.log('timed out', e));
breaker.on('reject', e => console.log('rejected', e));
breaker.on('open', () => console.log('opened'));
breaker.on('halfOpen', () => console.log('halfOpened'));
breaker.on('close', () => console.log('closed'));

let num = 0;
let sleepTime = 100;
let sleepIncrement = 100;
async function fetchBookings () {
  console.log(`request ${++num}`);
  if (sleepTime > 700) sleepTime = 0;
  return new Promise(resolve => {
    setTimeout(resolve,
      sleepTime += sleepIncrement, `${num} complete\n--`);
  });
}

function fallBack () {
  return 'fallback';
}

async function getData () {
  return breaker.fire().catch(console.error);
}

getData()
  .then(console.log)
  .catch(console.log)
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