read_stream

Build read-stream requests and decode read messages.

This module contains the sans-IO pieces for KurrentDB’s Streams/Read method when reading a single stream. It also defines the shared read message types used by stream subscriptions.

Use request to build a finite read request, and decode_message to turn each gRPC response frame into a typed ReadMessage.

Types

Configuration

opaque

Configuration for a finite stream read.

pub opaque type Configuration

Direction

Direction in which events are read.

pub type Direction {
  Forwards
  Backwards
}

Constructors

```
Forwards
```
Read from lower revisions to higher revisions.
```
Backwards
```
Read from higher revisions to lower revisions.

Position

A position in the KurrentDB transaction log.

pub type Position {
  NoPositionReturned
  Position(commit_position: Int, prepare_position: Int)
}

Constructors

```
NoPositionReturned
```

Position(commit_position: Int, prepare_position: Int)

ReadEvent

An event that was either recorded directly or resolved through a link.

pub type ReadEvent {
  Recorded(RecordedEvent)
  Resolved(link: RecordedEvent, event: RecordedEvent)
}

Constructors

```
Recorded(RecordedEvent)
```

Resolved(link: RecordedEvent, event: RecordedEvent)

ReadMessage

Message returned by a read or subscription stream.

KurrentDB can return data events, subscription lifecycle messages, checkpoints, and position metadata on the same gRPC stream.

pub type ReadMessage {
  ReadEvent(ReadEvent)
  SubscriptionConfirmed(String)
  Checkpoint(Position)
  CaughtUp(SubscriptionCheckpoint)
  FellBehind(SubscriptionCheckpoint)
  FirstStreamPosition(Int)
  LastStreamPosition(Int)
  LastAllStreamPosition(Position)
  ReadIgnored
}

Constructors

```
ReadEvent(ReadEvent)
```
```
SubscriptionConfirmed(String)
```
```
Checkpoint(Position)
```
```
CaughtUp(SubscriptionCheckpoint)
```
```
FellBehind(SubscriptionCheckpoint)
```
```
FirstStreamPosition(Int)
```
```
LastStreamPosition(Int)
```
```
LastAllStreamPosition(Position)
```
```
ReadIgnored
```

ReadRevision

Starting point for reading a stream.

pub type ReadRevision {
  FromStart
  FromEnd
  FromRevision(Int)
}

Constructors

```
FromStart
```
```
FromEnd
```
```
FromRevision(Int)
```

RecordedEvent

A stored event with its metadata and data.

metadata contains KurrentDB system metadata entries such as event type and content type. custom_metadata and data are the raw bytes written with the event.

pub type RecordedEvent {
  RecordedEvent(
    id: uuid.Uuid,
    stream: String,
    revision: Int,
    prepare_position: Int,
    commit_position: Int,
    metadata: List(#(String, String)),
    custom_metadata: BitArray,
    data: BitArray,
  )
}

Constructors

RecordedEvent(
  id: uuid.Uuid,
  stream: String,
  revision: Int,
  prepare_position: Int,
  commit_position: Int,
  metadata: List(#(String, String)),
  custom_metadata: BitArray,
  data: BitArray,
)

ResponseError

Errors that can occur while decoding a read message.

pub type ResponseError {
  GrpcError(kurrentdb.GrpcError)
  ReadStreamNotFound(String)
}

Constructors

```
GrpcError(kurrentdb.GrpcError)
```
```
ReadStreamNotFound(String)
```

SubscriptionCheckpoint

Checkpoint within a subscription stream.

pub type SubscriptionCheckpoint {
  NoSubscriptionCheckpoint
  StreamRevisionCheckpoint(Int)
  AllPositionCheckpoint(Position)
}

Constructors

```
NoSubscriptionCheckpoint
```
```
StreamRevisionCheckpoint(Int)
```
```
AllPositionCheckpoint(Position)
```

Values

configure

pub fn configure() -> Configuration

Create read configuration with default values.

Defaults are forwards, from the start of the stream, at most 1000 events, and link resolution disabled.

decode_message

pub fn decode_message(
  message: BitArray,
) -> Result(ReadMessage, ResponseError)

Decode one gRPC read response message.

Backends call this for each decoded gRPC frame. Stream-not-found gRPC errors are mapped to the operation-specific ReadStreamNotFound variant.

from_revision

pub fn from_revision(
  config: Configuration,
  revision: ReadRevision,
) -> Configuration

Set the revision to start reading from.

max_count

pub fn max_count(
  options: Configuration,
  max_count: Int,
) -> Configuration

Set the maximum number of events to read.

This applies only to finite reads. Subscriptions use a separate configuration type and continue until closed.

read_direction

pub fn read_direction(
  config: Configuration,
  direction: Direction,
) -> Configuration

Set the read direction for a stream read.

request

pub fn request(
  client: kurrentdb.Client,
  stream stream_name: String,
  config config: Configuration,
) -> request.Request(BitArray)

Build a finite Streams/Read request for a single stream.

resolve_links

pub fn resolve_links(
  options: Configuration,
  resolve_links: Bool,
) -> Configuration

Enable or disable link-to-event resolution.