# Modules > What each module of effect-cqrs exports. Everything is exported from `effect-cqrs` as a namespace, as in `import { Aggregate, ViewModel } from "effect-cqrs"`, and each module also has its own path, such as `effect-cqrs/ViewModel`. `PersonalDataNode` only has its own path, which keeps `node:crypto` out of code for browsers. ## Aggregate Defines aggregates. [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/Aggregate.ts) | Export | What it is | | --------------------------------------------------------------------- | ---------------------------------------------------------------------------------- | | `make()({ name, events, initial, projection, versions })` | Starts an aggregate, to which `.command(name, { payload, handler })` adds commands | | `evolve(aggregate, state, event, meta)` | Applies one event with the aggregate’s projection | | `historical(aggregate, tag, version, value)`, `Historical` | An event as an older version of its schema stored it | | `schemaVersion(aggregate, tag)`, `Versions` | The version new events are written in, and the type of `versions` | | `EventMeta`, `CommandContext` | What projections and handlers receive besides the event or payload | | `State`, `Event`, `CommandName`, `Payload`, `CommandError`, `Context` | Types derived from an aggregate | ## AggregateService Runs an aggregate against the event store. [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/AggregateService.ts) | Export | What it is | | --------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------ | | `make(aggregate, { maxRetries, stateCacheSize, commandIdsPerStream, snapshots })` | The service: `commands`, `dispatch`, `state`, `history` | | `SnapshotOptions` | `every`, `schema` and `version` of the snapshots | | `CommandOptions` | `commandId` and `expectedVersion`, the last argument of a typed command | | `CommandResult`, `HistoryEntry` | What a command and `history` return | | `UnknownCommand`, `InvalidCommand`, `WrongExpectedVersion`, `EventDecodeError` | Its errors, besides the store’s | | `CommandFailure`, `ReadError` | What every command, and every read, can fail with | | `commandIdKey` | The metadata key that records a command’s [`commandId`](https://effect-cqrs.dambox.ch/guides/commands/#retries-and-command-ids) | | `makeEventDecoder(aggregate, keys)`, `makeEventEncoder(aggregate, keys)` | Convert between stored JSON and an aggregate’s events, decrypting and encrypting personal fields with `keys` | | `MetricNames` | The names of the [metrics](https://effect-cqrs.dambox.ch/guides/commands/#metrics) the service records | ## CommandGateway One entry point for the commands of several aggregates, see [several aggregates](https://effect-cqrs.dambox.ch/guides/commands/#several-aggregates). [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/CommandGateway.ts) | Export | What it is | | ---------------------------------- | ----------------------------------------------------------------------------- | | `make(entries, { interceptors })` | The gateway over aggregates or their services: `send`, `dispatch`, `services` | | `Interceptor`, `CommandInfo` | What runs around every command, and what it learns about the command | | `Command` | The typed command `send` takes | | `UnroutableCommand` | `dispatch` can’t tell which aggregate a command is for | ## PersonalData Crypto-shredding of personal fields, see [personal data](https://effect-cqrs.dambox.ch/guides/personal-data/). [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/PersonalData.ts) | Export | What it is | | -------------------------------------------------------------------------------- | ------------------------------------------------------------------- | | `field(schema, { redacted, subject })` | Marks a field of an event as personal | | `forget(subject)` | Destroys the key of a subject and records it in the log | | `Keys`, `layerMemory`, `layerSql`, `make(backend)` | The keys of subjects, and where they are stored | | `MasterKey`, `layerMasterKey`, `layerMasterKeyConfig`, `layerMasterKeyEphemeral` | What wraps the keys of subjects | | `Backend`, `makeMemoryBackend`, `makeSqlBackend` | Key stores, to implement another | | `migrations({ table })` | The migrations of the key table, for `layerSql({ migrate: false })` | | `Cipher`, `webCrypto` | AES-256-GCM, on WebCrypto unless another cipher is provided | | `SubjectForgotten`, `PersonalDataError` | Its errors | | `streamName`, `subjectForgottenType` | Where forgetting is recorded | ## PersonalDataNode The [personal data](https://effect-cqrs.dambox.ch/guides/personal-data/#on-node) cipher on `node:crypto`, imported from `effect-cqrs/PersonalDataNode`. [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/PersonalDataNode.ts) | Export | What it is | | ------------- | ----------------------------------------------------------------------- | | `layerCipher` | Encrypts personal fields synchronously, in the same format as WebCrypto | | `cipher` | The `Cipher` it provides | ## EventVersions Older shapes of an event. [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/EventVersions.ts) | Export | What it is | | ------------------------- | ----------------------------------------------------------------------------- | | `from(schema)` | Starts a history at version 1, to which `.next(schema, upcast)` adds versions | | `decoders(tag, versions)` | One decoder per old version, all the way to the current one | | `current(versions)` | The version new events are written in | ## Causation Why events were recorded. [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/Causation.ts) | Export | What it is | | --------------------------------------- | ------------------------------------------------------------- | | `withCausation(causation)` | Runs an effect whose commands record these ids | | `causedBy(stored)`, `fromEvent(stored)` | Makes a stored event the cause of the commands an effect runs | | `CurrentCausation` | The reference that holds them, `undefined` outside any | ## Ids The ids the framework makes up, such as new correlations. [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/Ids.ts) | Export | What it is | | -------------------- | --------------------------------------------------------------- | | `IdGenerator` | The reference that makes them, `crypto.randomUUID()` by default | | `next` | A new id from the current generator | | `sequential(prefix)` | A generator of `prefix-1`, `prefix-2` and so on, for tests | ## Metadata What commands carry beside their payload, such as the software version. [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/Metadata.ts) | Export | What it is | | ------------------------ | --------------------------------------------------------------------------------------- | | `withMetadata(metadata)` | Runs an effect whose commands record this metadata on top of the current one | | `layer(metadata)` | Provides metadata to the services built on top, for values such as the software version | | `CurrentMetadata` | The reference that holds it, `{}` outside any | | `Metadata` | The type and schema of metadata: a JSON object | ## ViewModel Projects events into read models. [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/ViewModel.ts) | Export | What it is | | --------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------- | | `make({ name, aggregates, handlers, dispose, onForget, onFailure, transaction })` | Defines a view model. `onForget` erases what it stored about a [forgotten subject](https://effect-cqrs.dambox.ch/guides/personal-data/#view-models) | | `layer([...])` | Runs view models in the background and provides `ViewModels` | | `ViewModels` | The service: `replay`, `caughtUp`, `status`, `parked`, `retryParked` | | `stall`, `park({ attempts })`, `FailurePolicy` | What a view model does about an event that keeps failing, see [parking events](https://effect-cqrs.dambox.ch/guides/view-models/#parking-events) | | `sqlTransaction`, `Transaction` | Runs each batch with its checkpoint in one transaction, see [checkpoints in a transaction](https://effect-cqrs.dambox.ch/guides/view-models/#checkpoints-in-a-transaction) | | `Status`, `RetryParkedOptions`, `RetryParkedResult` | What `status` and `retryParked` give and take | | `MetricNames` | The names of the metrics view models record | | `ViewModelError`, `UnknownViewModel` | A handler’s failure, and a replay of an unknown name | ## ParkedEvents Events view models gave up on, see [parking events](https://effect-cqrs.dambox.ch/guides/view-models/#parking-events). [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/ParkedEvents.ts) | Export | What it is | | ----------------------------------------- | --------------------------------------------------------------- | | `ParkedEvents` | The service: `park`, `list`, `remove` | | `layerMemory`, `makeMemory` | Parked events in memory | | `layerSql({ table, migrate })`, `makeSql` | Parked events in a table, on SQLite or PostgreSQL | | `migrations({ table })` | The migrations of the table, for `layerSql({ migrate: false })` | | `ParkedEvent` | What it records, and its schema | ## Leases Which process runs each view model, see [several processes](https://effect-cqrs.dambox.ch/guides/view-models/#several-processes). [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/Leases.ts) | Export | What it is | | ----------------------------------------------------- | ---------------------------------------- | | `Leases` | The service: `acquire(name)` | | `layerMemory`, `memory` | Leases that are always held, the default | | `layerPostgres({ interval, prefix })`, `makePostgres` | Leases on PostgreSQL advisory locks | | `Lease` | A lease: `held` and `changes` | ## Saga Processes that span several aggregates, as durable workflows from `effect/workflow`, see [sagas](https://effect-cqrs.dambox.ch/guides/sagas/). [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/Saga.ts) | Export | What it is | | ------------------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------- | | `workflow(tag, { payload, idempotencyKey, success, error })` | Defines a saga’s workflow: `Workflow.make` with a `causation` field added to the payload | | `toLayer(workflow, execute)` | Registers the workflow’s body with the engine. Its commands record the event that started the saga as their cause | | `command(name, { execute, error })` | Runs a command as an activity, so a replay of the workflow returns the saved outcome instead of running it again | | `start(workflow, payload)` | Starts a run without waiting for it, and returns its execution id | | `make({ name, aggregates, handlers, onFailure })` | The trigger: a view model whose handlers start workflows with `start` | | `layer([...])` | Runs triggers in the background, apart from the view models, and provides `Sagas` | | `Sagas` | The service that manages the triggers, with what `ViewModel.ViewModels` has | | `SagaWorkflow` | The type of a workflow whose payload carries its causation | | `CausationSchema`, `CommandOutcome` | Schemas of that causation, and of what a saga keeps of a command it ran: aggregate, version and position | ## CommandApi Serves an aggregate over HTTP, see [integration](https://effect-cqrs.dambox.ch/guides/integration/#http). [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/CommandApi.ts) | Export | What it is | | -------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------- | | `group(aggregate, { name, prefix, state, errors })` | An `HttpApiGroup` with a `POST` endpoint per command, `history` and, with the `state` option, `state` | | `layer(api, name, service)` | Implements the group with an aggregate service, or an effect that makes one | | `InvalidCommandError`, `ConcurrencyConflictError`, `CommandRejected` | The errors it answers with `400`, `409` and `422` | | `commandResult(events)`, `historyEntry(events)` | Schemas of what a command and `history` answer | ## EventCatalog JSON Schema of events and commands, and a compatibility guard, see [integration](https://effect-cqrs.dambox.ch/guides/integration/#event-catalog). [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/EventCatalog.ts) | Export | What it is | | ------------------------------------------------------- | --------------------------------------------------------------------- | | `events(aggregate)`, `commands(aggregate)` | JSON Schema of every event version and command payload | | `document(aggregates, { title, version, description })` | An AsyncAPI 3.0 document of them | | `captureSamples(aggregates, { perVersion })` | Stored payloads of each event type and version, without personal data | | `saveSamples(path, samples)`, `readSamples(path)` | Keep samples in a JSON file | | `checkCompatibility(aggregate, samples)` | Fails with `IncompatibleSamples` when a sample no longer decodes | | `Sample`, `IncompatibleSamples` | A sample, and the guard’s error | ## Outbox Publishes events to other systems, see [integration](https://effect-cqrs.dambox.ch/guides/integration/#outbox). [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/Outbox.ts) | Export | What it is | | ------------------------------------------------------------------ | ------------------------------------------------------- | | `make({ name, aggregates, messages, publish, batchSize, linger })` | Defines an outbox | | `layer([...])` | Runs outboxes in the background and provides `Outboxes` | | `Outboxes` | The service: `published` and `status` | | `Message`, `Mapped`, `Mappings` | What is published, and what a mapping returns | | `OutboxError` | A failure to publish | ## EventStore The append-only log. [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/EventStore.ts) | Export | What it is | | ---------------------------------------------------- | -------------------------------------------------------------------------------------- | | `EventStore` | The service: `append`, `read`, `subscribe`, `head`, `changes` | | `layerMemory`, `makeMemory` | The store in memory | | `make(backend, options)`, `Backend`, `MakeOptions` | Builds a store on another database | | `groupCommit(appendGroup)` | Group commit for a backend: concurrent appends to different streams in one transaction | | `StoredEvent`, `EventFilter`, `AppendInput` | What it stores, selects and takes | | `eventId(event)` | An event’s id as a cause, like `account/alice@4` | | `toStored(input, event, index, position, timestamp)` | A new event’s stored form, for a backend | | `ConcurrencyConflict`, `EventStoreError` | Its errors | ## Checkpoints How far each view model has read. [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/Checkpoints.ts) | Export | What it is | | ------------- | ---------------------------- | | `Checkpoints` | The service: `get` and `set` | | `layerMemory` | Checkpoints in memory | ## SqliteEventStore and PostgresEventStore Durable stores through `effect/sql`. [SQLite](https://github.com/davidnussio/effect-cqrs/blob/main/src/SqliteEventStore.ts), [PostgreSQL](https://github.com/davidnussio/effect-cqrs/blob/main/src/PostgresEventStore.ts) | Export | What it is | | ---------------------------------- | ---------------------------------------------------------------------------------------- | | `layer(options)` | The event store, given a `SqlClient` | | `layerCheckpoints(options)` | Checkpoints in the same database | | `migrations(options)`, `Migration` | The schema as SQL, for your own migration tooling | | `Options` | `eventsTable`, `checkpointsTable`, `migrate`, `pollInterval`, and `listen` on PostgreSQL | ## Fixture Tests an aggregate. [Source](https://github.com/davidnussio/effect-cqrs/blob/main/src/Fixture.ts) | Export | What it is | | -------------------------- | -------------------------------------------------------------------------------- | | `make(aggregate)` | A fixture: `givenEvents`, `when`, `whenFails`, `inspectState`, `checkInvariants` | | `InvariantOptions`, `Step` | What `checkInvariants` takes, and one command it generates | | `Scenario`, `Outcome` | The chain, and what yielding it gives | | `ExpectationFailed` | The defect a failed expectation raises |