Add warming support

[Jamesking56]

In my use case, I'd like to add warming to the Browsershot Lambda so that requests are quicker but there doesn't seem to be an easy way to configure it:

https://hammerstone.dev/sidecar/docs/main/functions/warming

[stefanzweifel]

+1 on that!
I've wondered when the first message comes in about warming support. 😅
(I've also just now realised, that by default a Sidecar function doesn't support warming as the default number of instances is 0. No wonder my setup on 3.screeenly.com didn't work. 🙃)

I've been thinking for a while how we could accomplish this. The problem is, that the BrowsershotFunction-class is not resolved out of the IOC-container, but just "called" inside BrowsershotLambda here.

If the class would be injected, you could change the binding and pass a MyBrowsershotFunction that extends the package's BrowsershotFunction to BrowsershotLambda.
But that's quite a lot of work "just" for adding warming to the function.

Or we could introduce a config file, where user can define the number of instance they would like to be warmed.
In the same step, we could then also add config settings for runtime, memory and layers. As I think this could be stuff users would like to change too.
Adding a config file for such a "simple" package seems almost overkill.

But as Sidecar is currently not that flexible, I think adding a config/sidecar-browsershot.php config file is the simplest and most straightforward solution.
If you would like to contribute to the project, feel free to submit a PR adding such a config. If you currently don't have the time, no problem! I would then implement this in the next few days.

Created an issue for this: #17

[aarondfrancis]

Let me know if I need to change anything on the Sidecar end to accommodate this!

[stefanzweifel]

I've added a new sidebar-browsershot config in #18 which also contains a warming config.
https://github.com/stefanzweifel/sidecar-browsershot#warming

@Jamesking56 a new release has been created. So you should be able to just composer update wnx/sidecar-browsershot and then set SIDECAR_BROWSERSHOT_WARMING_INSTANCES=5 in your .env file and be good to go.

[Jamesking56]

Thanks @stefanzweifel for the speedy update! 👍