retryx
About
retryx (ritrɪ́ks) is a Promise-based retry workflow library.
Installation
$ npm install --save retryx
Usage
Flowchart
API
retryx
retryx(main [, options [, ...args]])main is a function returns Promise that might be rejected. Required
options is a object contains maxTries, waiter and other hooks. Optional
...args will be passed to main function call. Optional
options
{
maxTries: number,
timeout: number,
waiter: HookFunction,
retryCondition: HookFunction,
beforeTry: HookFunction,
afterTry: HookFunction,
beforeWait: HookFunction,
afterWait: HookFunction,
doFinally: HookFunction,
}HookFunction can receive current try count and last reject reason as arguments. See source.
maxTries
Attempts calling main function specified times or until succeeds.
Set -1 to retry unlimitedly.
default: 5
timeout
Sets the timeout.
Set -1 to no timeout.
default: -1
waiter
Hook function called before each retry. It's meant to return a Promise that resolves after specific duration.
default: exponential backoff. 200ms, 400ms, 800ms, 1600ms and so on.
See default waiter implementation. You can create custom waiter with wait function for shorthand.
retryCondition
Hook function called AFTER each try. If it returns falsy value, retrying will be abandoned even not reaching maxTries.
default: always return true
beforeTry
Hook function called BEFORE each try.
default: nothing to do
afterTry
Hook function called AFTER each try.
default: nothing to do
beforeWait
Hook function called BEFORE each wait.
default: nothing to do
afterWait
Hook function called AFTER each wait.
default: nothing to do
doFinally
Hook function called ONCE whether main function resolved or rejected.
default: nothing to do
Creating an instance
You can create a new instance of retryx with a custom config.
retryx.create(options)
const myRetryx = retryx.create({
maxTries: 100,
waiter: () => new Promise(r => setTimeout(r, 10)),
});Examples
With AWS SDK
const retryx = require("retryx");
const AWS = require("aws-sdk");
const ec2 = new AWS.EC2();
retryx(() => ec2.describeRegions().promise()).then(response => {
console.log(response);
});With axios
const retryx = require("retryx");
const axios = require("axios");
retryx(() => axios.get("http://example.com")).then(response => {
console.log(response.statusText);
});With async/await
import retryx from "retryx";
(async () => {
try {
const result = await retryx(() => {
const number = Math.round(Math.random() * 100);
if (number > 95) {
return number;
} else {
throw number;
}
});
console.log("success", result);
} catch (n) {
console.log("fail:", n)
}
})();With hooks
const retryx = require("retryx");
retryx(() => {
const number = Math.round(Math.random() * 100);
return number > 95 ? Promise.resolve(number) : Promise.reject(number);
}, {
maxTries: 100,
beforeWait: (tries) => console.log(`try #${tries} failed. wait 100 ms`),
waiter: () => new Promise((r) => setTimeout(r, 100)),
}).then(result => {
console.log(`success: ${result}`);
});TypeScript type inference
import retryx from "retryx";
(async () => {
let result = await retryx(() => 123);
result = "abc"; // ERROR: Type '"abc"' is not assignable to type 'number'.
})();TypeScript generics
import retryx from "retryx";
(async () => {
let result = await retryx<string>(() => { // Explicitly specifies type of promised value to return.
const number = Math.round(Math.random() * 100);
if (number < 50) {
throw new Error();
} else if (number < 80) {
return "good";
} else if (number < 90) {
return "great";
} else {
return number; // ERROR: Type 'number' is not assignable to type 'string | Promise<string>'.
}
});
})();See also
Development
$ git clone
$ cd retryx
$ yarn
Test.
$ yarn test