Sensible API Design at Netflix, Half 2: Protobuf FieldMask for Mutation Operations | by Netflix Know-how Weblog | Sep, 2021
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By Ricky Gardiner, Alex Borysov

In our earlier publish, we mentioned how we make the most of FieldMask as an answer when designing our APIs so that buyers can request the info they want when fetched through gRPC. On this weblog publish we’ll proceed to cowl how Netflix Studio Engineering makes use of FieldMask for mutation operations equivalent to replace and take away.

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Cash Heist (La casa de papel) / Netflix

Beforehand we outlined what a Manufacturing is and the way the Manufacturing Service makes gRPC calls to different microservices such because the Schedule Service and Script Service to retrieve schedules and scripts (aka screenplay) for a selected manufacturing equivalent to La Casa De Papel. We will take that mannequin and showcase how we will mutate explicit fields on a manufacturing.

Let’s say we wish to replace the format subject from LIVE_ACTION to HYBRID as our manufacturing has added some animated components. A naive means for us to resolve that is so as to add an updateProductionFormatRequest technique and gRPC endpoint simply to replace the productionFormat:

This enables us to replace the manufacturing format for a selected manufacturing however what if we then wish to replace different fields equivalent to titleand even a number of fields equivalent to productionFormat, schedule, and so on? Constructing on high of this we may simply implement an replace technique for each subject: one for Manufacturing format, one other for title and so forth:

This may turn into unmanageable when sustaining our APIs because of the variety of fields on the Manufacturing. What if we wish to replace a couple of subject and do it atomically in a single RPC? Creating further strategies for numerous mixtures of fields will result in an explosion of mutation APIs. This resolution isn’t scalable.

As a substitute of attempting to create each single mixture potential, one other resolution could possibly be to have an UpdateProduction endpoint that requires all fields from the patron:

The difficulty with this resolution is two-fold as the patron should know and supply each single required subject in a Manufacturing even when they simply wish to replace one subject such because the format. The opposite concern is that since a Manufacturing has many fields the request payload can turn into fairly giant significantly if the manufacturing has schedule or scripts info.

What if, as an alternative of all of the fields, we ship solely the fields we really wish to replace, and go away all different fields unset? In our instance, we’d solely set the manufacturing format subject (and ID to reference the manufacturing):

This might work if we by no means must take away or clean out any fields. However what if we wish to take away the worth of the title subject? Once more, we will introduce one-off strategies like RemoveProductionTitle, however as mentioned above, this resolution doesn’t scale nicely. What if we wish to take away a price of a nested subject such because the deliberate launch date subject from the schedule? We might find yourself including take away RPCs for each particular person nullable sub-field.

As a substitute of quite a few RPCs or requiring a big payload, we will make the most of a FieldMask for all our mutations. The FieldMask will listing all the fields we wish to explicitly replace. First, let’s replace our proto file so as to add within the UpdateProductionRequest, which is able to comprise the info we wish to replace from a manufacturing, and a FieldMask of what needs to be up to date:

Now, we will use a FieldMask to make mutations. We will replace the format by making a FieldMask for the format subject by utilizing the FieldMaskUtil.fromStringList() utility technique which constructs a FieldMask for an inventory of subject paths in a sure sort. On this case, we could have one sort, however will construct upon this instance later:

Since our FieldMask solely specifies the format subject that would be the solely subject that’s up to date even when we offer extra information in ProductionUpdateOperation. It turns into simpler so as to add or take away extra fields to our FieldMask by modifying the paths. Knowledge that’s offered within the payload however not added in a path of a FieldMask is not going to be up to date and easily ignored within the operation. However, if we omit a price it can carry out a take away mutation on that subject. Let’s modify our instance above to showcase this and replace the format however take away the deliberate launch date, which is a nested subject on the ProductionSchedule as “schedule.planned_launch_date”:

On this instance, we’re performing each replace and take away mutations as we’ve added “format” and “schedule.planned_launch_date” paths to our FieldMask. After we present this in our payload these fields shall be up to date to the brand new values, however when constructing our payload we’re solely offering the format and omitting the schedule.planned_launch_date. Omitting this from the payload however having it outlined in our FieldMask will operate as a take away mutation:



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