Retry

A typesafe promise based retry pattern

retry function

The retry function allows you to quickly retry a promise if it fails. Import it into your project as follows

1import retry from "@mrflish/retry";

the retry function takes several parameters the first one is the number of tries before giving up and returning the error that the function threw

1const result = await retry(num_of_tries, func_name, [func_param1, func_param2, ...], options);

retry will fail and throw if the function does not resolve before the maximum number of tries reaches its limit.

1import retry from "@mrflish/retry";
2
3let count = 1;
4const notSureIllResolve = async (param1: string, param2: number, param3: boolean[]) => {
5	if(count < 5) 
6		throw new Error(`Not yet... [${count++}]`);
7	return `About time ! [${count}]`;
8};
9
10
11try {
12    //the number of tries is not high enough to allow the function to resolve.
13    //retry will throw at the end of the 4th try.
14    const MAX_TRIES = 4;
15    const result = await retry(MAX_TRIES, notSureIllResolve, ["value of param1", 42, [true, false]]);
16    console.log(result);
17    
18} catch(error: any){
19    console.log(error.message);
20    //=> "Not yet... [4]"
21}
22

retry will resolve if the function resolves before the maximum number of tries reaches its limit

1import retry from "@mrflish/retry";
2
3let count = 1;
4const notSureIllResolve = async (param1: string, param2: number, param3: boolean[]) => {
5	if(count < 5) {
6		throw new Error(`Not yet... [${count++}]`);
7	}
8	return `About time ! [${count}]`;
9};
10
11
12try {
13    //retry will resolve at the 5th try
14    //MAX_TRIES is high enough to let the the function resolve
15    const MAX_TRIES = 6;
16    const result = await retry(MAX_TRIES, notSureIllResolve, ["value of param1", 42, [true, false]]);
17    console.log(result);
18    //=> "About time ! [5]"
19    
20} catch(error: any){
21    console.log(error.message);
22}

Retry class

The Retry class allows you to have more information about the execution of the function Import it into your project as follows

1import { Retry } from "@mrflish/retry";

the Retry construcor takes several parameters the first one is the function to try to run

1import { Retry } from "@mrflish/retry";
2const execute = new Retry(func_name, [func_param1, func_param2, ...], options);
3try {
4	//the number of tries is not high enough to allow the function to resolve.
5	//retry will throw at the end of the 4th try.
6	const MAX_TRIES = 4;
7
8    //Will trigger this event each time it tries again
9	execute.on("retry", (countDown, currentInterval) => {
10		/* Some things to do on each retry here */
11	});
12
13    //Will try trigger this event each time it fails
14    execute.on("failure", (error, countDown, currentInterval) => {
15		/* Some things to do on each failure here */
16	});
17
18	const result = await execute.try(MAX_TRIES);
19
20	console.log(result);
21		
22} catch(error: any){
23	console.log(error.message);
24	//=> "Not yet... [4]"
25}

options

Whether you use the function or the class, you can specify two options:

• interval

The interval option allows you to specify how long (in milliseconds) to wait before retrying after a failure. Set to 100ms by default

1const MAX_TRIES = 4;
2const execute = new Retry(notSureIllResolve, ["value of param1", 42, [true, false]], { interval: 500 });
3
4execute.on("retry", (countDown, currentInterval) => {
5    console.log(count, currentInterval);
6    console.log(`${count} -> ${currentInterval}`);
7    /* Some things to do on each retry here */
8});
9
10const result = await execute.try(MAX_TRIES);
11
12//OUTPUT
13//4 -> 500
14//3 -> 500
15//2 -> 500
16//Not yet... [4]

BinaryExponential

If the binaryExponential option is set to true, each new trial will have its time interval doubled. Set to false by default

1const MAX_TRIES = 5;
2const execute = new Retry(notSureIllResolve, ["value of param1", 42, [true, false]], { interval: 500, BinaryExponential: true });
3
4execute.on("retry", (countDown, currentInterval) => {
5    console.log(count, currentInterval);
6    console.log(`${count} -> ${currentInterval}`);
7    /* Some things to do on each retry here */
8});
9
10const result = await execute.try(MAX_TRIES);
11
12//OUTPUT
13//5 -> 500
14//4 -> 1000
15//3 -> 2000
16//2 -> 4000
17//About time ! [5]