API Guide

API Implementation Guide

Guide for implementing REST and GraphQL APIs with standard operations and scope patterns.

Standard Operations

APIs implement 6 standard operations:

1. create - Create new entity
2. get - Retrieve single entity
3. search - Query with filters and pagination
4. update - Update entity
5. delete - Delete entity (soft)
6. purge - Permanently remove entity (hard)

Batch operations: batch_update, batch_delete, batch_purge

Scope Prefix Rules

API layer only (Service/Repository layers don't use prefix)

Scoped Operations

Operations within a scope use {scope}_ prefix:

REST:

POST   /domains/{domain}/users        → domain_create_user
GET    /domains/{domain}/users/{id}   → domain_user
GET    /domains/{domain}/users         → domain_search_users
PATCH  /domains/{domain}/users/{id}   → domain_update_user
DELETE /domains/{domain}/users/{id}   → domain_delete_user

GraphQL:

mutation domainCreateUser(scope: DomainScope, input: ...)
query domainUser(scope: DomainScope, id: ID)
query domainSearchUsers(scope: DomainScope, filter: ...)

Admin Operations (No Scope)

Operations without scope use admin_ prefix (superadmin required):

REST:

POST   /admin/domains        → admin_create_domain
GET    /admin/domains/{id}   → admin_domain
GET    /admin/domains         → admin_search_domains

GraphQL:

mutation adminCreateDomain(input: ...)
query adminDomain(id: ID)
query adminSearchDomains(filter: ...)

REST API Patterns

Architecture

REST Handler → Processor → Service → Repository

Key Files:

• src/ai/backend/manager/api/{domain}/handler.py - Handlers
• src/ai/backend/manager/api/{domain}/adapter.py - Filters
• src/ai/backend/manager/api/adapter.py - Base adapter

Processor-Based Service Invocation

Core principle:

• REST/GraphQL handlers MUST call service methods through Processors
• Never call service methods directly from handlers
• Processors wrap service methods as Actions and provide cross-cutting concerns (hooks, metrics, monitoring)

Pattern:

1. Handler creates Action with operation parameters
2. Handler calls processor's wait_for_complete() with Action
3. Processor invokes corresponding service method and returns ActionResult

ActionProcessor responsibilities:

• Action-based service method invocation
• Hook execution (pre/post operation)
• Metrics collection and monitoring
• Error handling and logging

See complete examples:

• api/fair_share/handler.py:144 - Handler calling processor
• services/storage_namespace/processors.py:29-56 - Processor implementation
• services/processors.py - ActionProcessor base class

Scope Pattern

Scope defines access boundaries.

Repository Scope:

• src/ai/backend/manager/repositories/{domain}/types.py
• Example: repositories/fair_share/types.py
  • DomainFairShareSearchScope, ProjectFairShareSearchScope

Pattern:

• Frozen dataclass with scope params
• to_conditions() converts to query conditions

See complete examples:

• api/fair_share/handler.py - Scoped handler implementations

Scope Parameter Usage

Scope parameter is needed for:

1. search - Filter multiple items within scope

   domain_search_users(scope: DomainScope, filter: ...)
   

2. batch operations - Process multiple items within scope

   domain_batch_update_users(scope: DomainScope, ids: list[ID], ...)
   

Scope parameter is NOT needed for:

1. get - ID uniquely identifies item

   user(id: ID)  # ✅ No scope needed
   # domain_user(scope: DomainScope, id: ID)  # ❌ Unnecessary
   

2. update/delete/purge - ID uniquely identifies item

   update_user(id: ID, data: ...)  # ✅ No scope
   delete_user(id: ID)  # ✅ No scope
   

3. create - Scope info in data

   create_user(data: CreateUserData)  # data contains domain_name
   

Note: Scope prefix in API name (domain_search_users) is different from scope parameter (scope: DomainScope).

Filter Pattern

Filters convert API params to QueryCondition.

Adapter:

• api/adapter.py - BaseFilterAdapter
• api/fair_share/adapter.py - Domain adapters

Pattern:

• to_conditions(filters) → list[QueryCondition]
• to_orders(order_by) → list[QueryOrder]
• Adapter → BatchQuerier → Repository

See complete examples:

• api/fair_share/adapter.py - Filter adapters
• api/fair_share/handler.py - Handler implementations with BatchQuerier

Admin_ Prefix Pattern

Admin operations require superadmin check before processing.

Pattern:

• _check_superadmin(request) at handler start
• Raise InsufficientPermission if not superadmin

See complete examples:

• api/rbac/handler.py - Admin handler implementations

Pagination

REST uses offset-based pagination.

class PaginationQuery(BaseModel):
    offset: int = 0
    limit: int = 20

# Response
class SearchResult(BaseModel):
    items: list[Item]
    total_count: int
    offset: int
    limit: int

Client calculates: has_next = offset + limit < total_count

GraphQL Patterns

Architecture

GraphQL Resolver → check_admin_only (if admin) → Processor → Service → Repository

Key Files:

• src/ai/backend/manager/api/gql/{domain}/resolver/ - Resolvers
• src/ai/backend/manager/api/gql/types.py - Input types
• src/ai/backend/manager/api/gql/utils.py - Utilities

Type System Rules

Strawberry Runtime Evaluation:

• Strawberry types are evaluated at runtime
• NEVER use TYPE_CHECKING for Strawberry types (Connection, Filter, OrderBy, Input, Type)
• ALWAYS import Strawberry types directly at module level
• Only use TYPE_CHECKING for data layer types not used by Strawberry
• If lazy import needed: use strawberry.lazy() or string-based forward references

Naming Convention:

• All GraphQL types MUST have GQL suffix (DomainGQL, DomainScopeGQL, DomainFilterGQL)
• Distinguishes GraphQL types from data layer types
• Applies to: @strawberry.type, @strawberry.input, @strawberry.enum classes

Scope vs Filter:

• Scope: Required context parameters (resource_group, domain_name, project_id)
• Filter: Optional filtering conditions (name contains, status equals, created after)
• NEVER put optional fields in Scope - use Filter instead
• Scope fields must all be required (no default values, no Optional types)

Cross-Entity Reference Resolvers

When a GQL node references another entity node, use strawberry.lazy() to avoid circular imports. Strawberry requires runtime type resolution, so TYPE_CHECKING imports alone are insufficient.

Pattern:

# 1. TYPE_CHECKING: for static analysis (mypy)
if TYPE_CHECKING:
    from ai.backend.manager.api.gql.domain_v2.types.node import DomainV2GQL

# 2. Return type: Annotated with strawberry.lazy() for runtime resolution
# 3. Function body: runtime import + DataLoader
async def domain(self, info: Info[StrawberryGQLContext]) -> Annotated[
    DomainV2GQL,
    strawberry.lazy("ai.backend.manager.api.gql.domain_v2.types.node"),
]:
    from ai.backend.manager.api.gql.domain_v2.types.node import DomainV2GQL
    data = await info.context.data_loaders.domain_loader.load(self.domain_name)
    return DomainV2GQL.from_data(data)

Optional return type: | None must be outside Annotated[]:

) -> Annotated[DomainV2GQL, strawberry.lazy("...")] | None:  # ✅
) -> Annotated[DomainV2GQL | None, strawberry.lazy("...")]:   # ❌ lazy cannot resolve union

DataLoaders (info.context.data_loaders): Use DataLoaders instead of individual fetch functions to prevent N+1 queries. See api/gql/data_loader/data_loaders.py for available loaders.

See examples:

• api/gql/fair_share/types/domain.py - Cross-entity reference with DataLoader
• api/gql/domain_v2/types/node.py - DomainV2GQL with fair_shares/usage_buckets
• api/gql/fair_share/types/*.py - Scope and Filter patterns

Scope Pattern

Input Types:

• api/gql/types.py
  • ResourceGroupDomainScope, ResourceGroupProjectScope, ResourceGroupUserScope

Pattern:

• Strawberry @input maps to repository SearchScope
• GraphQL input → Repository scope type conversion

See complete examples:

• api/gql/types.py - Scope input types
• api/gql/fair_share/resolver/domain.py - Resolver implementations

Admin Check

Pattern:

• check_admin_only(info) at resolver start
• Raise InsufficientPermission if not superadmin

See complete examples:

• api/gql/utils.py - check_admin_only() utility
• api/gql/*/resolver/*.py - Admin resolver implementations

Pagination

GraphQL supports cursor-based (Relay spec).

@strawberry.type
class PageInfo:
    has_next_page: bool
    has_previous_page: bool
    start_cursor: str | None
    end_cursor: str | None

@strawberry.type
class UserConnection:
    edges: list[UserEdge]
    page_info: PageInfo
    total_count: int

See: api/gql/ for cursor pagination examples

REST vs GraphQL

Client SDK + CLI Integration

When implementing REST API, also implement:

1. ✅ SDK Function (client/func/{domain}.py)

   • Use @api_function decorator
   • Map to REST endpoint

2. ✅ CLI Command (client/cli/admin/{domain}.py)

   • Click command
   • Calls SDK function

Integration flow:

CLI → SDK → REST API → Processor → Service → Repository

See examples:

• src/ai/backend/client/func/admin.py - SDK
• src/ai/backend/client/cli/admin/user.py - CLI

Testing

See: /tdd-guide skill and tests/CLAUDE.md for complete testing strategies.

Test hierarchy:

Repository Tests → Real DB (with_tables)
Service Tests → Mock repositories
API Handler Tests → Mock processors
CLI Tests → Mock HTTP

Implementation Checklist

When implementing new API:

1. ✅ Repository (/repository-guide)

   • Implement standard operations
   • Define SearchScope

2. ✅ Service (/service-guide)

   • Define Actions/ActionResults
   • Implement service methods
   • Create processors

3. ✅ REST API

   • Handler with scope prefix
   • Admin check if needed
   • Filter adapter

4. ✅ GraphQL (optional)

   • Input types
   • Resolver with scope prefix
   • Admin check if needed

5. ✅ Client SDK

   • Add SDK function
   • @api_function decorator

6. ✅ CLI

   • Click command
   • Integrate with SDK

7. ✅ Tests

   • Repository (real DB)
   • Service (mock repo)
   • Handler (mock processors)
   • CLI (mock HTTP)

Related Documentation

• Service Layer: /service-guide - Actions, Processors
• Repository Layer: /repository-guide - Data access
• Testing: /tdd-guide - TDD workflow
• API README: src/ai/backend/manager/api/README.md

Examples

REST API:

• src/ai/backend/manager/api/fair_share/handler.py
• src/ai/backend/manager/api/rbac/handler.py

GraphQL:

• src/ai/backend/manager/api/gql/fair_share/resolver/domain.py
• src/ai/backend/manager/api/gql/types.py

Client SDK/CLI:

• src/ai/backend/client/func/admin.py
• src/ai/backend/client/cli/admin/user.py

Summary

Standard operations:

• create, get, search, update, delete, purge
• batch_update, batch_delete, batch_purge

Scope prefix (API only):

• Scoped: {scope}_operation (domain_create_user)
• Admin: admin_operation (admin_create_domain)

Key patterns:

• Scope → SearchScope → QueryCondition
• Filter → Adapter → QueryCondition
• Admin → check permission first

Integration:

• REST API + SDK + CLI (unified stack)
• GraphQL (separate, optional)

Next steps:

1. Implement repository (/repository-guide)
2. Implement service (/service-guide)
3. Implement API handlers
4. Add SDK + CLI
5. Write tests (/tdd-guide)