A promise-based object pool for Node.js.
$ npm install thingy-poolThe factory is responsible for creating and destroying the objects you want to pool. The factory can also validate the objects if needed.
const Api = require('some-api');
const factory = {
create: async () => {
const api = new Api();
await api.connect();
return api;
},
destroy: async api => {
await api.disconnect();
console.log(`${api} has been disconnected!`);
},
validate: async api => {
const response = await api.ping();
const isValid = response && response.time < 200;
return isValid;
},
};See Options for a complete list of options
const Pool = require('thingy-pool');
const factory = require('./myObjectFactory');
const options = { minSize: 2, maxSize: 5, shouldValidateOnDispatch: true };
const pool = new Pool(factory, options);// or const fetchSomething = async () => {
async function fetchAndPrint(something) {
const thingy = await pool.acquire();
const result = await thingy.fetch(something);
pool.release(thingy);
console.log(`fetched ${something}: ${result}`);
}
fetchAndPrint('something'); // fetched something: result
fetchAndPrint('somethingElse'); // fetched somethingElse: resultObjects must be released back to the pool after they are used. Alternatively, pool.use() can be passed a callback.
async function fetchAndPrint(something) {
const result = await pool.use(thingy => thingy.fetch(something));
console.log(`fetched ${something}: ${result}`);
}
fetchAndPrint('something'); // fetched something: result
fetchAndPrint('somethingElse'); // fetched somethingElse: result| Property | Type | Default | Description |
|---|---|---|---|
| minSize | number | 0 |
The minimum number of objects the pool will try to maintain including borrowed objects |
| maxSize | number | 1 |
The maximum number of objects the pool can manage including objects being created |
| defaultTimeoutInMs | number | null | 30000 |
The default time in milliseconds requests for objects will time out |
| maxPendingRequests | number | null | null |
The number of requests that can be queued if the pool is at the maximum size and has no objects available |
| idleCheckIntervalInMs | number | null | null |
The interval the pool checks for and removes idle objects. Requires softIdleTimeInMs or hardIdleTimeInMs |
| maxIdleToRemove | number | null | null |
The max objects that can be removed each time the pool checks for idle objects. null will check all objects |
| softIdleTimeInMs | number | null | null |
The amount of time an object must be idle before being eligible for soft removal. Will not remove object if available objects is at or below minSize |
| hardIdleTimeInMs | number | null | null |
The amount of time an object must be idle before being eligible for hard removal. Removes object regardless of minSize |
| shouldAutoStart | boolean | true |
Should the pool start creating objects to reach the minimum size as soon as it is created? |
| shouldValidateOnDispatch | boolean | false |
Should the pool check objects with factory.validate before dispatching them to requests? |
| shouldValidateOnReturn | boolean | false |
Should the pool check objects with factory.validate when they are being returned? |
| shouldUseFifo | boolean | true |
Should the pool dispatch objects using first in first out (FIFO)? |
Options with type number must be positive integers with the exception of minSize and maxPendingRequests which also accept 0. Think of null more like None. This is mainly to distinguish between maxPendingRequests: null which does not limit pending requests and maxPendingRequests: 0 which will reject requests if there a no objects available and no additional objects can be created. Not sure if that's useful...
Request an object from the Pool. If no objects are available and the pool is below the maximum size, a new one will be created
| Parameter | Type | Default | Description |
|---|---|---|---|
| options.priority | number | 0 |
The priority for the request. The higher the number the higher the priority |
| options.timeoutInMs | number | null | 30000 |
Time in milliseconds before the request times out |
const thingy = await pool.acquire();
// With custom priority
const thingy = await pool.acquire({ priority: 5 });
// With custom timeout
const thingy = await pool.acquire({ timeoutInMs: 5000 });
// With custom priority and timeout
const thingy = await pool.acquire({ priority: 10, timeoutInMs: 1000 });Destroys all pooled objects that are currently available. Resolves after objects have been destroyed
pool.getInfo(); // { size: 5, available: 2, borrowed: 3, ...moreInfo }
await pool.clear();
pool.getInfo(); // { size: 3, available: 0, borrowed: 3, ...moreInfo }pool.getInfo() → {PoolInfo}
Current object counts and pool's state
pool.getInfo().available; // 2
// or
const { available, borrowed, size, state } = pool.getInfo();pool.getOptions() → {Options}
Current pool options
pool.getOptions().defaultTimeoutInMs; // 30000
// or
const { maxSize, maxPendingRequests } = pool.getOptions();Total number of objects in the pool. Includes objects being created and excludes objects being destroyed
pool.getSize(); // 3Checks if the object is part of the pool
pool.has(thingy); // trueChecks if the object is currently borrowed
pool.isBorrowed(thingy); // trueCurrent pool state as a string
pool.getState(); // 'STARTED'| Parameter | Type | Description |
|---|---|---|
| event | PoolEvent | The name of the event to listen for |
| callback | function | A function that can take the argument from the event |
pool.on('poolDidStart', () => console.log('The pool has started!'));
pool.on('poolDidStop', () => console.log('The pool has stopped!'));This is how you could stop the pool if the factory isn't creating objects correctly
let createErrorCount = 0;
function handleFactoryCreateError(error) {
console.warn('An error occurred while trying to create an object');
console.log(error);
createErrorCount += 1;
if (createErrorCount > 5) {
console.error('Too many creation errors. Stopping the pool!');
pool.stop();
}
}
pool.on('factoryCreateError', handleFactoryCreateError);Returns the object back to the pool for future use
const thingy = await pool.acquire();
pool.getInfo(); // { size: 5, available: 2, borrowed: 3, ...moreInfo }
const result = await thingy.doSomethingAsync();
await pool.release(thingy);
pool.getInfo(); // { size: 5, available: 3, borrowed: 2, ...moreInfo }Returns the object to the pool and destroys it
const thingy = await pool.acquire();
pool.getInfo(); // { size: 5, available: 2, borrowed: 3, ...moreInfo }
const result = await thingy.doSomethingAsync();
await pool.releaseAndDestroy(thingy);
pool.getInfo(); // { size: 4, available: 2, borrowed: 2, ...moreInfo }Starts the pool
await pool.start();
const thingy = await pool.acquire();Stops the pool
const thingy = await pool.acquire();
const finalResult = await thingy.doSomethingAsync();
pool.release(thingy);
pool.stop();Use a pooled object with a callback and release to object automatically
| Parameter | Type | Default | Description |
|---|---|---|---|
| callback | function | A function that takes a pooled object as an argument | |
| options.priority | number | 0 |
The priority for the request. The higher the number the higher the priority |
| options.timeoutInMs | number | null | 30000 |
Time in milliseconds before the request times out |
const something = await pool.use(thingy => thingy.fetch('something'));
console.log(`I fetched ${something}`);
// or
pool.use(async thingy => {
const something = await thingy.fetch('something');
console.log(`I fetched ${something}`);
});
// with custom options
const something = await pool.use(thingy => thingy.fetch('something'), { priority: 10, timeoutInMs: 1000 });
console.log(`I fetched ${something}`);const poolInfo = pool.getInfo();| Property | Type | Description |
|---|---|---|
| available | number | Number of objects that are available for requests |
| beingCreated | number | Number of objects being created |
| beingDestroyed | number | Number of objects being destroyed. Not included in the total pool size |
| beingValidated | number | Number of objects being validated. The sum of beingValidatedForDispatch and beingValidatedForReturn |
| beingValidatedForDispatch | number | Number of objects being validated before attempting to dispatch to a request |
| beingValidatedForReturn | number | Number of objects being validated before being returned to available objects |
| pendingRequests | number | Number of requests waiting for an object |
| borrowed | number | Number of objects currently borrowed |
| notBorrowed | number | Number of objects not currently borrowed |
| size | number | Total number of objects in the pool. Includes objects being created and excludes objects being destroyed |
| state | string | The current pool state |
The pool is an event emitter and can emit the following events:
| Name | Arguments | Description |
|---|---|---|
| factoryCreateError | error |
An error ocurred while trying to create an object. Likely an error from factory.create |
| factoryDestroyError | error |
An error ocurred while trying to destroy an object. Likely an error from factory.destroy |
| factoryValidateError | error |
An error ocurred while trying to validate an object. Likely an error from factory.validate |
| poolDidStart | Pool has started and initial objects have been created to reach the minimum pool size | |
| poolDidStop | Pool has stopped and all objects have been destroyed |
Thingy Pool was heavily inspired by Generic Pool. Thanks to @coopernurse and everyone that has contributed.
Thanks @vitomilana for your continued interest in this project and helping the team stay on track.
I built this as a way to learn more about programing. I really appreciate everyone out there asking and answering questions that are helping people they will never meet.
Special Thanks:
- Sandi Metz
- Brad Traversy
- Discord.js
- Airbnb JavaScript Style Guide
- JavaScript Algorithms and Data Structures
The above people and repositories really helped me while working on this. I'm including them to say thanks and maybe someone else will find them useful.
Copyright 2020 Pat Brown
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
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