Add Federation Support #98

samisuteria · 2023-02-05T11:11:19Z

A basic implementation of federation. Some issues I have and could use guidance:

~~Using AnyCodable as a dependency~~ Used the Map type from GraphQL
~~Where to store JSONEncoder/Decoder for reusability~~ Use schema coders
~~Users having to implement ~~FederationContext~~/FederationResolver and~~ No custom protocol for federation resolver. Users still need to copy the SDL in directly
~~How to apply directives to fields/types (ie: @key(fields: "id"), @inaccessible, @shareable )~~ Key has been implemented on Type and maps to a function in the resolver.
~~Supporting older versions of Swift (any FederationContext requires 5.7)~~ ~~Updated FederationResolver protocol to offer a method for older versions of Swift~~ No longer needed

Sources/Graphiti/Federation/FederationSchema.swift

d-exclaimation · 2023-02-08T06:24:25Z

How to apply directives to fields/types (ie: @key(fields: "id"), @inaccessible, @Shareable )

@NeedleInAJayStack is directive support already in Graphiti?

NeedleInAJayStack · 2023-02-08T16:10:47Z

How to apply directives to fields/types (ie: @key(fields: "id"), @inaccessible, @Shareable )

@NeedleInAJayStack is directive support already in Graphiti?

Not at the moment, but it's deinitely a highly sought-after feature

I should say, just for clarity, that the GraphQL standard directives 'skip' and 'include' are supported, but custom directives like Apollo Federation relies on are not supported today.

samisuteria · 2023-02-09T00:09:18Z

Not at the moment, but it's deinitely a highly sought-after feature

I can work on that feature - would you prefer directive support before merging in federation?

NeedleInAJayStack · 2023-02-09T18:36:15Z

Awesome, thank you so much @samisuteria! Yeah, from my understanding federation support typically uses custom directives, so solving custom directives in a general way first makes sense to me. Thanks again, and great work so far!

samisuteria · 2023-02-10T05:00:40Z

Federation can work without directives in the application code. If you are writing schema first (I'm not sure the split between schema-first and code-first in the GraphQL ecosystem) you can enable federation without directives. As long as the service sdl query returns the schema federation will work correctly. Even Apollo's reference server avoids using directives in the code and just loads the schema from the file system here.

query {
   _service { sdl }
}

If you check out the samisuteria/graphiti branch on https://github.com/samisuteria/apollo-federation-subgraph-compatibility/ and run make test subgraph=swift-graphiti you'll see it passes all tests except federated tracing (which seems like a much larger project based on: https://www.apollographql.com/docs/graphos/metrics/sending-operation-metrics#tracing-format) and it appears about half the subgraph libraries have warning levels of support for it https://www.apollographql.com/docs/federation/building-supergraphs/supported-subgraphs .

*************
Federation v1 compatibility
*************
_service PASS
@key (single) PASS
@key (multi) PASS
@key (composite) PASS
repeatable @key PASS
@requires PASS
@provides PASS
federated tracing WARNING

*************
Federation v2 compatibility
*************
@link PASS
@shareable PASS
@tag PASS
@override PASS
@inaccessible PASS

I still plan on working on adding directive/sdl support for Graphiti but I think this PR is ready for review and can be used by people who are schema-first.

d-exclaimation · 2023-02-10T05:10:36Z

I still plan on working on adding directive/sdl support for Graphiti but I think this PR is ready for review and can be used by people who are schema-first.

Sounds good for me. Nice work 👍 . While It's probably a bit awkward atm given you can't really fully do schema-first or use directive with Graphiti, those feature can be separated and worked on later with future PR / releases.

NeedleInAJayStack · 2023-02-11T01:26:54Z

Great info @samisuteria! Thanks for walking me through that, and in that case I'm totally ok with this going in before directive support.

Sorry about the delay - I'll get a review in this weekend.

NeedleInAJayStack

Overall, I like the direction a lot. However, I think there may be some opportunities to align this more with the existing patterns (similar to how Connection was added). Things like integrating Key definition directly into the schema DSL instead of using a resolver protocol, and creating relevant GraphQL types during the SchemaBuilder.build phase.

If you don't mind, I've done some scratch work on the tip of your branch to make sure some of these ideas work out, and I'd like to see if the changes are acceptable to you. I'll post a link in a bit.

NeedleInAJayStack · 2023-02-11T16:44:10Z

Sources/Graphiti/Federation/FederationEntity.swift

+}
+
+public extension FederationEntity {
+    static var typename: String { Reflection.name(for: Self.self) }


Is this 'self' name reflection compatible with types that we have aliased in our GraphQL schema? For example:

Type(LocationObject.self, as: "Location") { Field("id", at: \.id) Field("name", at: \.name) }

I don't think it's compatible with the one in the schema. I just provided a default implementation for simplicity but the user can override it if needed. I did that here since there was a User type already defined in another test. https://github.com/GraphQLSwift/Graphiti/pull/98/files#diff-7086f136baa260fe52dc5fa6c66acf11b265a563f76708d829293b38aa10937cR84

NeedleInAJayStack · 2023-02-11T16:53:00Z

Sources/Graphiti/Federation/FederationResolver.swift

+    associatedtype Context
+    static var encoder: JSONEncoder { get }
+    static var decoder: JSONDecoder { get }
+    var sdl: String { get }
+    func entity(context: Context, key: FederationEntityKey, group: EventLoopGroup) -> EventLoopFuture<FederationEntity?>


This resolver protocol duplicates quite a bit of structure from the Schema type itself (things like coders and generic Context). Also, I'm a little wary to require protocol conformance on our resolver types, since that's not something we've done in the past.

I agree and was not a fan of it.

NeedleInAJayStack · 2023-02-11T18:21:09Z

Sources/Graphiti/Federation/SchemaBuilder+Federation.swift

+extension SchemaBuilder where Resolver: FederationResolver, Resolver.Context == Context {
+    @discardableResult
+    /// Enable federation to add additional capabilities for federation subgraph support
+    public func enableFederation() -> Self {
+        let federationSchema = PartialSchema<Resolver, Context>(


Could we do this in a similar way to the Apollo Connection support where we handle it during the schema creation itself?

I didn't see the Connection code but looking at it now - it really does seem the way to go.

NeedleInAJayStack · 2023-02-11T18:28:24Z

Sources/Graphiti/Federation/FederationResolver.swift

+    associatedtype Context
+    static var encoder: JSONEncoder { get }
+    static var decoder: JSONDecoder { get }
+    var sdl: String { get }


For this parameter, we need to define our SDL string separately and ensure it corresponds to the schema definition we coded, right? It would be awesome if we could generate the SDL automatically from the defined schema, but I know that's probably a bigger task.

Yea I would really prefer to not require the SDL since that requires users to put federation specific code into their schema. Maybe have a way of verifying the the supplied SDL to the built schema to make sure all types/fields/keys are included?

NeedleInAJayStack · 2023-02-13T05:32:34Z

Tests/GraphitiTests/ProductAPI/ProductResolver.swift

+    static let entityKeys: [(entity: FederationEntity.Type, keys: [FederationEntityKey.Type])] = [
+        (Product.self, [Product.EntityKey1.self, Product.EntityKey2.self, Product.EntityKey3.self]),
+        (DeprecatedProduct.self, [DeprecatedProduct.EntityKey.self]),
+        (ProductResearch.self, [ProductResearch.EntityKey.self]),
+        (ProductUser.self, [ProductUser.EntityKey.self]),
+    ]


We map up our Entities to Keys through the resolver already - is there any way we could reuse that definition instead of requiring it twice?

NeedleInAJayStack · 2023-02-13T06:17:21Z

@samisuteria See what you think of this twist on your implementation: https://github.com/NeedleInAJayStack/Graphiti/tree/federation_jay

If you're okay with it, we can pull those commits into this MR.

samisuteria · 2023-02-13T07:00:40Z

@NeedleInAJayStack I really like the changes on your branch and the Key implementation / mapping to the Resolver argument types is a much better way to implement federation.

The syntax for defining keys in the schema seems a bit complicated (anytime you have multiple builder closures in a function).

What do you think of something like this? It would just require keys: [KeyComponent<ObjectType, Resolver, Context>] to be mutable.

Type(Product.self) {
    Field("id", at: \.id)
    Field("sku", at: \.sku)
    Field("package", at: \.package)
    Field("variation", at: \.variation)
    Field("dimensions", at: \.dimensions)
    Field("createdBy", at: \.createdBy)
    Field("notes", at: \.notes)
    Field("research", at: \.research)
}
.key(at: ProductResolver.getProduct1) {
    Argument("id", at: \.id)
}
.key(at: ProductResolver.getProduct2) {
    Argument("sku", at: \.sku)
    Argument("package", at: \.package)
}
.key(at: ProductResolver.getProduct3) {
    Argument("sku", at: \.sku)
    Argument("variation", at: \.variation)
}

Eventually when the library can generate the SDL itself, I imagine other directives would work the same way and the syntax would be similar to SwiftUI's ViewModifier

NeedleInAJayStack · 2023-02-13T07:08:09Z

@samisuteria Ooo, I love that idea. You're right, it looks cleaner and better preserves the public API

NeedleInAJayStack · 2023-02-13T20:58:34Z

@samisuteria I just implemented your suggestion on my branch. If you like it, feel free to pull those commits into this MR. Thanks again!

samisuteria · 2023-02-14T07:07:40Z

Just pulled in the changes - thank you so much for the help on this :)

samisuteria · 2023-02-14T08:30:51Z

This is a useful dockerfile if you're on Apple Silicon and want to test older versions of Swift:

FROM swift:5.6-focal as swift5.6

WORKDIR /build

# Cache dependencies
COPY ./Package.* ./
RUN swift package resolve

COPY . .
RUN swift test --parallel

FROM swiftarm/swift:5.5.3-debian-buster as swift5.5

WORKDIR /build

# Cache dependencies
COPY ./Package.* ./
RUN swift package resolve

COPY . .
RUN swift test --parallel

FROM swiftarm/swift:5.4.3-focal-multi-arch as swift5.4

WORKDIR /build

# Cache dependencies
COPY ./Package.* ./
RUN swift package resolve

COPY . .
RUN swift test --parallel

FROM swift:latest

WORKDIR /build

# Make sure all stages actually run
COPY --from=swift5.6 ./build ./build-5.6
COPY --from=swift5.5 ./build ./build-5.5
COPY --from=swift5.4 ./build ./build-5.4

NeedleInAJayStack

Thanks for fixing the CI @samisuteria!

NeedleInAJayStack self-requested a review February 5, 2023 13:58

d-exclaimation reviewed Feb 6, 2023

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Sources/Graphiti/Federation/FederationSchema.swift Outdated Show resolved Hide resolved

samisuteria added 16 commits February 7, 2023 21:41

add product api

196d3aa

add tests

273db2d

add federation related protocols and extensions

0f0cdc1

add extension to type component for keys

627bef2

add federation to schema builder

f2a60d4

update federation tests

dc6a6cb

add lookup to context

bae9424

make entities work with federation

a0951e1

make resolver work with federation

2b31166

add keys to schema

7940fd2

setup and teardown can not be in an extension

6b72624

add checks for swift 5.7

ef88c70

share service resolver between versions

ff739fd

use instance based partial schema

69feb33

async in tests

aaeedd6

throwing setup

33a1cc2

samisuteria added 3 commits February 7, 2023 22:25

reduce required functions in federation resolver protocol

27d913b

remove unused key (need directives first)

6e0da5f

update usage guide

07fdc68

NeedleInAJayStack reviewed Feb 13, 2023

View reviewed changes

NeedleInAJayStack added 14 commits February 13, 2023 23:06

feature: Adds federated Key type and builder

53cf8c9

feature: Adds federation details to TypeProvider and Schema

a1dd60b

feature: Adds Key definition to Type

313e542

feature: Adds Federated schema assets

83fe4f3

feature: Type.update defines __resolveReference field

9532ac2

feature: Query creation adds federated types and queries

37aaa4a

test: Updates federated tests to new format

cd8139b

refactor: Deletes old federation constructions

12c7622

doc: Updates usage guide

98d6652

fix: Adds key/field name validation

95195fb

feature: Type Keys are mutable

d6d91bc

feature: Changes key definition to fluent builder

c84e661

feature: Removes Key resultBuilder support

907d77b

chore: Fixes warning

5294ea0

samisuteria added 2 commits February 13, 2023 23:33

fix compile issue for swift 5.6

e4899bb

fix swift 5.4 error

237ca0b

NeedleInAJayStack approved these changes Feb 14, 2023

View reviewed changes

NeedleInAJayStack merged commit 14f378c into GraphQLSwift:main Feb 14, 2023

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Add Federation Support #98

Add Federation Support #98

samisuteria commented Feb 5, 2023 •

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Add Federation Support #98

Add Federation Support #98

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