[5.x] Make autoscaling rate configurable

[hivokas]

This PR makes autobalancing rate configurable for applications that use the auto queue balancing strategy.

Problem

Imagine we have the following supervisor config:

'supervisor-1' => [
    'connection' => 'redis',
    'queue' => ['high', 'low'],
    'balance' => 'auto',
    'minProcesses' => 5,
    'maxProcesses' => 150,
    'tries' => 1,
],

Let's say we dispatch 1,000 jobs to the low queue for something like an email campaign. Currently, autobalancing will only adjust the number of workers at a maximum rate of ±1 worker every 3 seconds. So, it will take a long time to increase the number of workers from 5 (minProcesses) to 150 (maxProcesses). There's no way to change this.

Solution

With this PR we make the autobalancing rate configurable:

/*
|--------------------------------------------------------------------------
| Autoscaling
|--------------------------------------------------------------------------
|
| Here you may define the autoscaling settings used by your application.
|
*/

'autoscaling' => [
    'cooldown' => 3,
    'max_shift' => 1,
],

cooldown - the number of seconds to wait in between auto-scaling attempts
max_shift - the maximum number of processes to increase or decrease per one scaling

Breaking changes

This PR doesn't introduce any breaking changes since the default values (for cooldown and max_shift) are consistent with the current values. Even if someone upgrades without adding these config values, it will still use those defaults.

However, I decided that it might be better to point this PR to the 5.x branch.

Benefit

Let's perform a test by dispatching 750 jobs at once (each job sleeps for 5 seconds) without this change. We can see it takes 135 seconds to process these jobs.

Let's set 'cooldown' => 1 and 'max_shift' => 50 and perform the same test one more time.

This time, it took only 30 seconds, because autoscaling happens much faster.

Related issues

#658

[taylorotwell]

What if you want the cool_down and max_shift to be different for each supervisor configuration? Any reason it's not part of that configuration?

[hivokas]

What if you want the cool_down and max_shift to be different for each supervisor configuration?

Hm, that sounds like a good idea.

Any reason it's not part of that configuration?

The reason is I didn't think about that.

[hivokas]

Does the following example of config look good for you @taylorotwell?

'supervisor-1' => [
    'connection' => 'redis',
    'queue' => ['high', 'low'],
    'balance' => 'auto',
    'minProcesses' => 5,
    'maxProcesses' => 150,
    'tries' => 1,
    'maxShift' => 20,
    'cooldown' => 1,
],

[hivokas]

If yes, I'll work on moving cooldown and max_shift to the supervisor config.

[taylorotwell]

Maybe rename cooldown to balanceCooldown?

Other than that it looks good.

[hivokas]

@taylorotwell I've updated the PR. balanceCooldown and autoScaleMaxShift are the part of a supervisor configuration now.
Also, I've updated the default config a bit.

[taylorotwell]

Renamed autoScaleMaxShift to balanceMaxShift.

[hivokas]

Thanks for merging!