Fix frontend memory leaks

[teosarca]

Steps to reproduce

It seems the frontend consumes quite a lot of memory (might be some memory leaks?).
My test case was:

• open a window, e.g. receipt schedules https://w101.metasfresh.com:8443/window/540196
• open chrome task manager (in windows that's shift-ESC)
• refresh the frontend page couple of times (e.g. 10 times)
• observe how the memory consumption is rising

Expected behavior

Identify the fix the memory leaks.

Thanks @wiadev for bringing this up.

[wiadev]

Yes, memory does leaking in application.

Possible places (not limited to):

1. Trace Redux reducers for optimal state updates
2. Check for components referring when not needed to large objects (and arrays) don't allowing to be freed by garbage collector
3. Make sure to optimize re-creating of components when not needed

Major memory wasters:

1. DocumentList
2. Forms

Other resource-consuming sources might include Websockets, need to carefully verify what they're referring and ensure data gets freed when not needed.

[wiadev]

please keep in mind that this is needed, but risky change

[wiadev]

this story will result large impact on many areas on site. So needs to be carefully checked both on dev and QA ends. QA phase might take significant time.

[cadavre]

Tested on Chrome, macOS.

Page with /window/540196 takes regularly ~270MB.
This page (GH issue) takes ~210MB in comparison.

After refreshing page once or 20x it grows to ~310MB but never more.

Might be OS GC issue? Because it isn't one for me and if it is "risky change" and "will result large impact on many areas on site" maybe it's worth making some more research on different test envs?

Attaching detailed performance scan for 10x refresh:

(Chrome 59.0.3071.115, macOS Sierra 10.12.6)

Chart on the bottom is memory. GC works quite well and instant, also after all refreshes gets to initial value.

Please provide your env and performance dumps.

[wiadev]

Try to switch between forms and document lists for example.
Not refreshing single page.
Otherwise figures aren't quite correct

[cadavre]

Made around 15 switches between one list and different document:

In task manager never more than 360MB. On chart you can see that memory levels are on almost-initial level at the end.

Could you provide yours chart for comparison?

[metas-lc]

IT
tested the case above -> works fine