Contracts and Adapters

Forze follows hexagonal architecture (ports and adapters). The core idea is simple: the application layer declares what capabilities it needs through protocol interfaces (contracts), and infrastructure packages provide how those capabilities are implemented (adapters). The application never depends on a specific adapter.

How it works

The application layer defines contracts: protocol interfaces describing required capabilities
Infrastructure packages provide adapters: concrete implementations of those protocols
A dependency plan wires adapters to contracts at startup
Usecases resolve contracts from execution context; they never import adapter classes

Switching from Postgres to Mongo means changing the dependency plan, not the usecase code.

Contract catalog

Document storage

Split into read and write ports for CQRS flexibility:

DocumentReadPort[R]: read-only operations:

Method	Signature	Purpose
`get`	`(pk, *, for_update?, return_fields?) -> R \| JsonDict`	Fetch one document by ID
`get_many`	`(pks, *, return_fields?) -> Sequence[R] \| Sequence[JsonDict]`	Fetch multiple by IDs
`find`	`(filters, *, for_update?, return_fields?) -> R \| None`	Find one by filter
`find_many`	`(filters?, limit?, offset?, sorts?, *, return_fields?) -> (list[R], int)`	Paginated query
`count`	`(filters?) -> int`	Count matching documents

DocumentWritePort[R, D, C, U]: mutation operations:

Method	Signature	Purpose
`create`	`(dto) -> R`	Create a document
`create_many`	`(dtos) -> Sequence[R]`	Batch create
`update`	`(pk, dto, *, rev?) -> R`	Partial update
`update_many`	`(pks, dtos, *, revs?) -> Sequence[R]`	Batch update
`touch`	`(pk) -> R`	Bump `last_update_at` only
`kill`	`(pk) -> None`	Hard delete
`delete`	`(pk, *, rev?) -> R`	Soft delete
`restore`	`(pk, *, rev?) -> R`	Restore from soft delete

Both ports also have *_many batch variants for all applicable operations.

Transaction management

TxManagerPort: manages transaction boundaries:

Method	Purpose
`transaction()`	Returns an async context manager for a transaction scope
`scope_key()`	Returns the scope key identifying this tx manager kind

TxScopedPort: marks a port as transaction-aware. The execution context validates that scoped ports match the active transaction kind.

Cache

CachePort: document-level caching with read and write sub-protocols:

Method	Purpose
`get(pk)`	Retrieve a cached document
`get_many(pks)`	Retrieve multiple cached documents
`set(pk, data)`	Store a document in cache
`invalidate(pk)`	Remove a document from cache
`invalidate_many(pks)`	Remove multiple documents from cache

Counter

CounterPort: namespace-scoped atomic counters:

Method	Purpose
`incr(suffix?, by?)`	Increment and return new value
`incr_batch(count, suffix?)`	Increment by count and return final value
`decr(suffix?, by?)`	Decrement and return new value
`reset(suffix?, value?)`	Reset to a specific value

Search

SearchReadPort[R]: full-text search:

Method	Purpose
`search(query, filters?, limit?, offset?, sorts?, *, options?, return_model?, return_fields?)`	Search with optional filters and pagination

Object storage

StoragePort: S3-style blob storage:

Method	Purpose
`upload(filename, data, description?, *, prefix?)`	Upload an object
`download(key)`	Download an object
`delete(key)`	Delete an object
`list(limit, offset, *, prefix?)`	List objects with pagination

Queue (message queue)

QueueReadPort[M]: consume messages from a queue:

Method	Purpose
`receive(queue, *, limit?, timeout?)`	Receive a batch of messages
`consume(queue, *, timeout?)`	Async iterator over messages
`ack(queue, ids)`	Acknowledge processed messages
`nack(queue, ids, *, requeue?)`	Reject messages, optionally re-queue

QueueWritePort[M]: produce messages to a queue:

Method	Purpose
`enqueue(queue, payload, *, type?, key?, enqueued_at?)`	Send a single message
`enqueue_many(queue, payloads, *, type?, key?, enqueued_at?)`	Send a batch

Pub/Sub

PubSubPublishPort[M]: publish to a topic:

Method	Purpose
`publish(topic, payload, *, type?, key?, published_at?)`	Publish a message

PubSubSubscribePort[M]: subscribe to topics:

Method	Purpose
`subscribe(topics, *, timeout?)`	Async iterator over messages

Stream

StreamReadPort[M]: read from an append-only log:

Method	Purpose
`read(stream_mapping, *, limit?, timeout?)`	Read entries from streams
`tail(stream_mapping, *, timeout?)`	Async iterator that follows new entries

StreamGroupPort[M]: consumer group reads:

Method	Purpose
`read(group, consumer, stream_mapping, *, limit?, timeout?)`	Group read
`tail(group, consumer, stream_mapping, *, timeout?)`	Group tail
`ack(group, stream, ids)`	Acknowledge entries

StreamWritePort[M]: append to a stream:

Method	Purpose
`append(stream, payload, *, type?, key?, timestamp?)`	Append an entry

Idempotency

IdempotencyPort: deduplicate HTTP requests:

Method	Purpose
`begin(op, key, payload_hash)`	Check for cached response
`commit(op, key, payload_hash, snapshot)`	Store response for future dedup

Workflow

WorkflowPort: orchestrate long-running processes:

Method	Purpose
`start(name, id, args, queue?)`	Start a workflow instance
`signal(id, signal, data)`	Send a signal to a running workflow

Context ports

TenantContextPort: ambient tenant identity for multi-tenant routing:

Method	Purpose
`get()`	Return current tenant ID
`set(tenant_id)`	Bind tenant for the current context

ActorContextPort: ambient actor identity for audit trails:

Method	Purpose
`get()`	Return current actor ID
`set(actor_id)`	Bind actor for the current context

Dependency keys

Each contract has a corresponding DepKey for registration and resolution. Integration modules register adapters under these keys; the execution context resolves them.

doc = self.ctx.doc_read(project_spec)     # resolves DocumentReadDepKey
cache = self.ctx.cache(cache_spec)         # resolves CacheDepKey
counter = self.ctx.counter("tickets")      # resolves CounterDepKey
storage = self.ctx.storage("attachments")  # resolves StorageDepKey

For contracts without convenience methods on ExecutionContext, use dep() directly:

from forze.application.contracts.pubsub import PubSubPublishDepKey

publish = ctx.dep(PubSubPublishDepKey)(ctx, spec)

Wiring adapters

Integration modules register their adapters at dependency plan build time:

from forze.application.execution import Deps, DepsPlan

deps_plan = DepsPlan.from_modules(
    lambda: Deps.merge(
        PostgresDepsModule(client=pg_client, ...)(),
        RedisDepsModule(client=redis_client)(),
        S3DepsModule(client=s3_client)(),
    ),
)

Deps.merge() combines containers and raises CoreError if any key is registered twice. This catches misconfigured plans early.

Testing

Tests stub contracts with in-memory or fake implementations. The forze_mock package provides ready-made adapters for all contracts, backed by shared in-memory state:

from forze.application.execution import Deps, DepsPlan, ExecutionContext
from forze_mock import MockDepsModule

module = MockDepsModule()
deps_plan = DepsPlan.from_modules(module)
ctx = ExecutionContext(deps=deps_plan.build())

doc = ctx.doc_read(project_spec)
result = await doc.get(some_uuid)

You can also build a Deps container manually with only the ports your test needs:

deps = Deps({
    DocumentReadDepKey: lambda ctx, spec, cache=None: FakeDocReadAdapter(),
})
ctx = ExecutionContext(deps=deps)

No real databases or external services are needed for unit testing business logic. See the Mock integration guide for full details.