a.js

const genericPool = require("generic-pool");

const factory = {
    create: function() {  
        return new Promise(function(resolve, reject){
            setTimeout(function(){
                reject(new Error('cannot create resource'))
            }, 1000)
        })
    },
    destroy:  function () { return Promise.resolve() }
}

const opts = {
  acquireTimeoutMillis: 5000
}

const myPool = genericPool.createPool(factory, opts)

myPool.on('factoryCreateError', function(err){
    console.log('factory create error, %s',err)
})

myPool.acquire()
.then(function() {
    console.log('acquired a resource')
}).catch(function(err){
    console.log('failed to acquire resource: %s', err)
})
.then(function(){
    console.log('pool stats', {
        min: myPool.min,
        max: myPool.max,
        size: myPool.size,
        available: myPool.available,
    })
})

setInterval(function(){
    // just here to keep the event loop spinning
}, 5000)

output

factory create error, Error: cannot create resource
factory create error, Error: cannot create resource
factory create error, Error: cannot create resource
factory create error, Error: cannot create resource
failed to acquire resource: TimeoutError: ResourceRequest timed out
pool stats { min: 0, max: 1, size: 1, available: 0 }
factory create error, Error: cannot create resource

## END OF OUTPUT ##