Having issues with retry interceptor

[acommodari]

Hello I'm trying to use the new retry interceptor along with RetryOptions to create exponential jittered backoff. However im running into some weird issues and I'm not sure if this is a bug or I'm just not understanding how to use the interpreter properly.

First i created a basic http server to test requests against:

import http from "http";

const server = http.createServer((req, res) => {
  if (req.url === "/api" && req.method === "GET") {
    if (Math.random() > 0.5) {
      res.writeHead(500, { "Content-Type": "text/plain" });
      res.end("500 Internal Server Error");
    } else {
      res.writeHead(200, { "Content-Type": "application/json" });
      res.end(JSON.stringify({ message: "Hello from the API endpoint!" }));
    }
  } else {
    res.writeHead(404, { "Content-Type": "text/plain" });
    res.end("404 Not Found");
  }
});

const port = 3000;
server.listen(port, () => {
  console.log(`Server is running on port ${port}`);
});

Then I tried doing a basic retry like this:

import { Client, interceptors } from "undici";

const { retry } = interceptors;

const client = new Client("http://localhost:3000").compose(
  retry({
    retry: function (err, context, callback) {
      console.log("retrying", {
        err: err.code,
        state: context.state,
        opts: context.opts.retryOptions,
      });
      if (context.state.counter >= context.opts.retryOptions.maxRetries) {
        callback(err);
        return;
      }
      setTimeout(() => callback(null), context.opts.retryOptions.timeout);
    },
    maxRetries: 3,
    minTimeout: 400,
    maxTimeout: 10000,
  })
);

let res;
const start = performance.now();
try {
  res = await client.request({
    path: "/api",
    method: "GET",
    throwOnError: true,
  });
} catch (error) {
  console.log(error.name);
}
const end = performance.now();

res ? console.log(await res.body.json()) : console.log("No response");
console.log(end - start);

Then when i try to log out the results i get this weird output

retrying {
  err: 'UND_ERR_REQ_RETRY',
  state: { counter: 1, currentTimeout: undefined },
  opts: {
    retry: [Function: retry],
    retryAfter: true,
    maxTimeout: 10000,
    timeout: 400,
    timeoutFactor: 2,
    maxRetries: 3,
    methods: [ 'GET', 'HEAD', 'OPTIONS', 'PUT', 'DELETE', 'TRACE' ],
    statusCodes: [ 500, 502, 503, 504, 429 ],
    errorCodes: [
      'ECONNRESET',
      'ECONNREFUSED',
      'ENOTFOUND',
      'ENETDOWN',
      'ENETUNREACH',
      'EHOSTDOWN',
      'EHOSTUNREACH',
      'EPIPE',
      'UND_ERR_SOCKET'
    ]
  }
}
retrying {
  err: 'UND_ERR_REQ_RETRY',
  state: { counter: 3, currentTimeout: undefined },
  opts: {
    retry: [Function: retry],
    retryAfter: true,
    maxTimeout: 10000,
    timeout: 400,
    timeoutFactor: 2,
    maxRetries: 3,
    methods: [ 'GET', 'HEAD', 'OPTIONS', 'PUT', 'DELETE', 'TRACE' ],
    statusCodes: [ 500, 502, 503, 504, 429 ],
    errorCodes: [
      'ECONNRESET',
      'ECONNREFUSED',
      'ENOTFOUND',
      'ENETDOWN',
      'ENETUNREACH',
      'EHOSTDOWN',
      'EHOSTUNREACH',
      'EPIPE',
      'UND_ERR_SOCKET'
    ]
  }
}
RequestRetryError
No response
423.162216

as we can see here it only retried twice and the counter skipped count 2?
also the response time was only 423 ms it should be at least 800 ms if it retried 2 times right?

what am i doing wrong here 🤔

[metcoder95]

👋
I tried to reproduce your issue and so far, behavioural speaking is working as expected, though I found the bug around the counter and I'm opening a PR for it.

Outocme after exhausting a retry counter of 4

Server is running on port 3000
retrying {
  err: 'UND_ERR_REQ_RETRY',
  state: { counter: 1 },
  opts: {
    retry: [Function: retry],
    retryAfter: true,
    maxTimeout: 10000,
    timeout: 400,
    timeoutFactor: 2,
    maxRetries: 4,
    methods: [ 'GET', 'HEAD', 'OPTIONS', 'PUT', 'DELETE', 'TRACE' ],
    statusCodes: [ 500, 502, 503, 504, 429 ],
    errorCodes: [
      'ECONNRESET',
      'ECONNREFUSED',
      'ENOTFOUND',
      'ENETDOWN',
      'ENETUNREACH',
      'EHOSTDOWN',
      'EHOSTUNREACH',
      'EPIPE',
      'UND_ERR_SOCKET'
    ]
  }
}
retrying {
  err: 'UND_ERR_REQ_RETRY',
  state: { counter: 2 },
  opts: {
    retry: [Function: retry],
    retryAfter: true,
    maxTimeout: 10000,
    timeout: 400,
    timeoutFactor: 2,
    maxRetries: 4,
    methods: [ 'GET', 'HEAD', 'OPTIONS', 'PUT', 'DELETE', 'TRACE' ],
    statusCodes: [ 500, 502, 503, 504, 429 ],
    errorCodes: [
      'ECONNRESET',
      'ECONNREFUSED',
      'ENOTFOUND',
      'ENETDOWN',
      'ENETUNREACH',
      'EHOSTDOWN',
      'EHOSTUNREACH',
      'EPIPE',
      'UND_ERR_SOCKET'
    ]
  }
}
retrying {
  err: 'UND_ERR_REQ_RETRY',
  state: { counter: 3 },
  opts: {
    retry: [Function: retry],
    retryAfter: true,
    maxTimeout: 10000,
    timeout: 400,
    timeoutFactor: 2,
    maxRetries: 4,
    methods: [ 'GET', 'HEAD', 'OPTIONS', 'PUT', 'DELETE', 'TRACE' ],
    statusCodes: [ 500, 502, 503, 504, 429 ],
    errorCodes: [
      'ECONNRESET',
      'ECONNREFUSED',
      'ENOTFOUND',
      'ENETDOWN',
      'ENETUNREACH',
      'EHOSTDOWN',
      'EHOSTUNREACH',
      'EPIPE',
      'UND_ERR_SOCKET'
    ]
  }
}
retrying {
  err: 'UND_ERR_REQ_RETRY',
  state: { counter: 4 },
  opts: {
    retry: [Function: retry],
    retryAfter: true,
    maxTimeout: 10000,
    timeout: 400,
    timeoutFactor: 2,
    maxRetries: 4,
    methods: [ 'GET', 'HEAD', 'OPTIONS', 'PUT', 'DELETE', 'TRACE' ],
    statusCodes: [ 500, 502, 503, 504, 429 ],
    errorCodes: [
      'ECONNRESET',
      'ECONNREFUSED',
      'ENOTFOUND',
      'ENETDOWN',
      'ENETUNREACH',
      'EHOSTDOWN',
      'EHOSTUNREACH',
      'EPIPE',
      'UND_ERR_SOCKET'
    ]
  }
}
RequestRetryError
No response
1230.755166

[acommodari]

awesome! thank you 😄 !

[acommodari]

One question though should the counter start at 1 or at 0?

wouldnt that affect the minTimeout * timeoutFactor ** counter?

wouldnt you want the count to start at 0 or at least (counter - 1)? shouldnt the first retry delay be the minTimeout?

[metcoder95]

Done the PR, thanks for the feedback!