4210 Fetch and scope variants for shop in ProductsRenderer only once

[kristinalim]

What? Why?

• References [Performance] UK Server is a temperamental beast #4210

This caches in instance variable ProductsRenderer#all_variants_for_shop so that the variants do not have to be fetched and scoped twice for the two times that this method is called.

This is a small code change that could considerably reduce the RAM and processing done for RefreshProductsCacheJob. It takes some time for Ruby garbage collection to happen, so for a shop that has thousands of variants in their order cycle, this could mean number_of_variants + number_of_variant_overrides fewer objects in memory, in addition to the I think only slightly reduced number of SQL queries.

(Maybe garbage collection is something we could look into too, if we're not doing this already.)

What should we test?

For below:

• Supplier stock settings - What you can set in Bulk Edit Products page
• Variant override stock settings - What you can set in Inventory page

Do the following with an open OC:

1. Create a new variant with unlimited stock (supplier).
2. Add the variant to the OC. The variant should be available in the shop.
3. Test the following:
   • 0 limited stock (supplier) - not available in shop
   • Positive limited stock (supplier) - available in the shop
4. In the Inventory page, add a variant override for the variant.
5. Test the following:
   • 0 limited stock (variant override) - not available in shop
   • Positive limited stock (variant override) - available in shop
   • 0 limited stock (variant override) again - wait for variant to disappear again
   • Unlimited stock (variant override) - available in shop

Release notes

• Fetch and scope variants for shop in ProductsRenderer used in RefreshProductsCacheJob only once.

Changelog Category: Changed

[sauloperez]

It takes some time for Ruby garbage collection to happen,

(Maybe garbage collection is something we could look into too, if we're not doing this already.)

Very good point. It's worth enabling Datadog's Ruby GC monitoring. According to https://docs.datadoghq.com/tracing/setup/ruby/ it will fetch Garbage collection statistics which will allow us to validate this claim.

[sauloperez]

@all_variants_for_shop = is redundant here

[Matt-Yorkley]

Ah I missed that. Yeah, that shouldn't be there.

[kristinalim]

Whoops! Sorry, that was from an earlier change. Fixed already.

[sauloperez]

Unfortunately, until we don't get rid of VariantOverrides we have a blocker to properly improve the performance of many endpoints and jobs.