Use a BatchManger explictly outside of hooks

[DaddyWarbucks]

This is a feature idea and not a bug

I know that I can use the excludes and timeout options to configure the batchClient to behave a certain way. But I have found some use cases where I think it would be nice to use some kind of static method to run some actions in a batch. For example,

// I only want to run these actions in Batch. For whatever reason I don't want them batched with
// other calls, or maybe I am not even using batchClient plugin at all.

const actions = [
  app.service('users').find(),
  app.service('items').find()
];

// Replace this
const results = await Promise.all(actions);

// with this
const results = await BatchManger.all(actions, managerConfig)

This could also be used server side. For example, the Promise.all(actions) does not allow the actions to share a dataloader from feathers-batchloader (unless you manually created one and passed to it, which is a perfectly viable option). Using BatchManger.all(actions, managerConfig) would go through the batch-service hooks and automatically share a dataloader (if setup, of course) and anything else that the batch-service may help out with.

[DaddyWarbucks]

Rethinking this, the above code would not really work. My main goal of this would be to use it server side to batch calls together so that they can easily share an AppLoader from feathers-batchloader v2 (which is a just fancy dataloader). This can currently be accomplished two ways.

const loader = new AppLoader({ app });

const actions = [
  app.service('users').find({ loader }),
  app.service('items').find({ loader })
];

const results = await Promise.all(actions);

// Provided batch-service creates a loader and passes it
// to all of its batched calls
const actions = [
  ['users', 'find'],
  ['items', 'find'],
];

const results = await app.service('batch-service').create(actions);

So I am just spitballing ideas to allow the developer to call the batch service in a more familiar way and outside of hooks. batchClient accomplishes this by "intercepting" regular services calls and building up the options.

Maybe something like

const result = await BatchManager.all((service) => {
  return [
    service('users').find(),
    service('items').find(),
  ]
})

This is likely not even needed. I just wanted to capture my thoughts on it. But, I really like the idea of using this serverside. I can see some huge performance boosts when using resolvers. If all of the resolvers were batched, then they would go through that batch-service hooks first which could pass the same AppLoader to all of them.

[DaddyWarbucks]

A simple solution to this on the server side would be to simply allow the create method to accept promises instead of just config. We can already use the service server side like

app.service('batch').create({ calls: [
  ['users', 'find', {}],
  ['posts', 'find', {}]
 ]})

We could update this to also accept promises. They are functionally the same, but using promises is more natural

app.service('batch').create({ calls: [
  app.service('users').find(),
  app.service('posts').find()
]})

This would be a simple change here:

feathers-batch/lib/index.js

Line 20 in 4c924e1

const [method, serviceName, ...args] = payload;

if (typeof payload === 'function') {
  return payload;
}
const [method, serviceName, ...args] = payload;
...rest

That accomplishes the main goal on the server, which is to be able to use it with simpler syntax.