@castore/dynamodb-event-storage-adapter
v1.25.3
Published
DRY Castore EventStorageAdapter implementation using DynamoDB
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DynamoDB Event Storage Adapter
DRY Castore EventStorageAdapter
implementation using AWS DynamoDB.
📥 Installation
# npm
npm install @castore/dynamodb-event-storage-adapter
# yarn
yarn add @castore/dynamodb-event-storage-adapter
This package has @castore/core
and @aws-sdk/client-dynamodb
(above v3) as peer dependencies, so you will have to install them as well:
# npm
npm install @castore/core @aws-sdk/client-dynamodb
# yarn
yarn add @castore/core @aws-sdk/client-dynamodb
Table of content
This library exposes two adapters:
DynamoDbSingleTableEventStorageAdapter
which can plug several event stores to a single DynamoDB table.- (deprecated)
DynamoDbEventStorageAdapter
which needs a DynamoDB table per event store.
The legacy DynamoDbEventStorageAdapter
is still exposed for backward compatibility. It will be deprecated and renamed LegacyDynamoDbEventStorageAdapter
in the v2, to be finally removed in the v3.
Documentation:
DynamoDbSingleTableEventStorageAdapter
👩💻 Usage
import { DynamoDBClient } from '@aws-sdk/client-dynamodb';
import { DynamoDbSingleTableEventStorageAdapter } from '@castore/dynamodb-event-storage-adapter';
const dynamoDbClient = new DynamoDBClient({});
const pokemonsEventsStorageAdapter = new DynamoDbSingleTableEventStorageAdapter(
{
tableName: 'my-table-name',
dynamoDbClient,
},
);
// 👇 Alternatively, provide a getter
const pokemonsEventsStorageAdapter =
new DynamoDbSingleTableEventStorageAdapter({
tableName: () => process.env.MY_TABLE_NAME,
dynamoDbClient,
});
const pokemonsEventStore = new EventStore({
...
storageAdapter: pokemonsEventsStorageAdapter,
});
This will directly plug your EventStore to DynamoDB 🙌
🤔 How it works
This adapter persists aggregates in separate partitions: When persisting an event, its aggregateId
, prefixed by the eventStoreId
, is used as partition key (string attribute) and its version
is used as sort key (number attribute).
A Global Secondary Index is also required to efficiently retrieve the event store aggregates ids (listAggregateIds
operation). Only initial events (version = 1
) are projected. A KEYS_ONLY
projection type is sufficient.
// 👇 Initial event
{
"aggregateId": "POKEMONS#123", // <= Partition key
"version": 1, // <= Sort key
"eventStoreId": "POKEMONS", // <= initialEvents index partition key
"timestamp": "2022-01-01T00:00:00.000Z", // <= initialEvents index sort key
"type": "POKEMON_APPEARED",
"payload": { "name": "Pikachu", "level": 42 },
"metadata": { "trigger": "random" }
}
// 👇 Non-initial event
{
"aggregateId": "POKEMONS#123",
"version": 2,
// Event is not projected on initialEvents index (to limit costs)
"timestamp": "2023-01-01T00:00:00.000Z",
"type": "POKEMON_LEVELED_UP"
}
The getEvents
method (which is used by the getAggregate
and getExistingAggregate
methods of the EventStore
class) uses consistent reads, so is always consistent.
The pushEvent
method is a write operation and so is always consistent. It is conditioned to avoid race conditions, as required by the Castore specifications.
By design, the listAggregateIds
operation can only be eventually consistent (GSIs reads cannot be consistent).
📝 Examples
Note that if you define your infrastructure as code in TypeScript, you can directly use this package instead of hard-coding the below values:
import {
EVENT_TABLE_PK, // => aggregateId
EVENT_TABLE_SK, // => version
EVENT_TABLE_INITIAL_EVENT_INDEX_NAME, // => initialEvents
EVENT_TABLE_EVENT_STORE_ID_KEY, // => eventStoreId
EVENT_TABLE_TIMESTAMP_KEY, // => timestamp
} from '@castore/dynamodb-event-storage-adapter';
CloudFormation
{
"Type": "AWS::DynamoDB::Table",
"Properties": {
"AttributeDefinitions": [
{ "AttributeName": "aggregateId", "AttributeType": "S" },
{ "AttributeName": "version", "AttributeType": "N" }
{ "AttributeName": "eventStoreId", "AttributeType": "S" },
{ "AttributeName": "timestamp", "AttributeType": "S" }
],
"KeySchema": [
{ "AttributeName": "aggregateId", "KeyType": "HASH" },
{ "AttributeName": "version", "KeyType": "RANGE" }
],
"GlobalSecondaryIndexes": [
{
"IndexName": "initialEvents",
"KeySchema": [
{ "AttributeName": "eventStoreId", "KeyType": "HASH" },
{ "AttributeName": "timestamp", "KeyType": "RANGE" }
],
"Projection": "KEYS_ONLY"
}
]
}
}
CDK
import { Table, AttributeType, ProjectionType } from 'aws-cdk-lib/aws-dynamodb';
const { STRING, NUMBER } = AttributeType;
const { KEYS_ONLY } = ProjectionType;
const pokemonsEventsTable = new Table(scope, 'PokemonEvents', {
partitionKey: {
name: 'aggregateId',
type: STRING,
},
sortKey: {
name: 'version',
type: NUMBER,
},
});
pokemonsEventsTable.addGlobalSecondaryIndex({
indexName: 'initialEvents',
partitionKey: {
name: 'eventStoreId',
type: STRING,
},
sortKey: {
name: 'timestamp',
type: STRING,
},
projectionType: KEYS_ONLY,
});
Terraform
resource "aws_dynamodb_table" "pokemons-events-table" {
hash_key = "aggregateId"
range_key = "version"
attribute {
name = "aggregateId"
type = "S"
}
attribute {
name = "version"
type = "N"
}
attribute {
name = "eventStoreId"
type = "S"
}
attribute {
name = "timestamp"
type = "S"
}
global_secondary_index {
name = "initialEvents"
hash_key = "eventStoreId"
range_key = "timestamp"
projection_type = "KEYS_ONLY"
}
}
🤝 EventGroups
This adapter implements the EventGroups API using the DynamoDb Transactions API:
import { EventStore } from '@castore/core';
// 👇 TransactWriteItems N events simultaneously
await EventStore.pushEventGroup(
// events are correctly typed 🙌
eventStoreA.groupEvent(eventA1),
eventStoreA.groupEvent(eventA2),
eventStoreB.groupEvent(eventB),
...
);
Note that:
- All the event stores involved in the transaction need to use the
DynamoDbSingleTableEventStorageAdapter
- This util inherits of the
TransactWriteItem
API limitations: It can target up to 100 distinct events in one or more DynamoDB tables within the same AWS account and in the same Region.
🔑 IAM
Required IAM permissions for each operations:
getEvents
(+getAggregate
,getExistingAggregate
):dynamodb:Query
pushEvent
:dynamodb:PutItem
listAggregateIds
:dynamodb:Query
on theinitialEvents
index
📸 ImageParser
This library also exposes a useful ImageParser
class to parse DynamoDB stream images from a DynamoDbSingleTableEventStorageAdapter
. It will build a correctly typed NotificationMessage
ouf of a stream image, unmarshalling it, removing the prefix of the aggregateId
in the process and validating the eventStoreId
:
import { ImageParser } from '@castore/dynamodb-event-storage-adapter';
const imageParser = new ImageParser({
sourceEventStores: [pokemonsEventStore, trainersEventStore],
});
// 🙌 Typed as EventStoreNotificationMessage<
// typeof pokemonsEventStore
// | typeof trainersEventStore...
// >
const notificationMessage = imageParser.parseImage(
streamImage,
// 👇 Optional options
unmarshallOptions,
);
Legacy DynamoDbEventStorageAdapter
👩💻 Usage
import { DynamoDBClient } from '@aws-sdk/client-dynamodb';
import { DynamoDbEventStorageAdapter } from '@castore/dynamodb-event-storage-adapter';
const dynamoDbClient = new DynamoDBClient({});
const pokemonsEventsStorageAdapter = new DynamoDbEventStorageAdapter({
tableName: 'my-table-name',
dynamoDbClient,
});
// 👇 Alternatively, provide a getter
const pokemonsEventsStorageAdapter = new DynamoDbEventStorageAdapter({
tableName: () => process.env.MY_TABLE_NAME,
dynamoDbClient,
});
const pokemonsEventStore = new EventStore({
...
storageAdapter: pokemonsEventsStorageAdapter
})
This will directly plug your EventStore to DynamoDB 🙌
🤔 How it works
This adapter persists aggregates in separate partitions: When persisting an event, its aggregateId
is used as partition key (string attribute) and its version
is used as sort key (number attribute).
A Global Secondary Index is also required to efficiently retrieve the event store aggregates ids (listAggregateIds
operation). Only initial events (version = 1
) are projected. A KEYS_ONLY
projection type is sufficient.
// 👇 Initial event
{
"aggregateId": "123", // <= Partition key
"version": 1, // <= Sort key
"isInitialEvent": 1, // <= initialEvents index partition key
"timestamp": "2022-01-01T00:00:00.000Z", // <= initialEvents index sort key
"type": "POKEMON_APPEARED",
"payload": { "name": "Pikachu", "level": 42 },
"metadata": { "trigger": "random" }
}
// 👇 Non-initial event
{
"aggregateId": "123",
"version": 2,
// Event is not projected on initialEvents index (to limit costs)
"timestamp": "2023-01-01T00:00:00.000Z",
"type": "POKEMON_LEVELED_UP"
}
The getEvents
method (which is used by the getAggregate
and getExistingAggregate
methods of the EventStore
class) uses consistent reads, so is always consistent.
The pushEvent
method is a write operation and so is always consistent. It is conditioned to avoid race conditions, as required by the Castore specifications.
By design, the listAggregateIds
operation can only be eventually consistent (GSIs reads cannot be consistent).
📝 Examples
Note that if you define your infrastructure as code in TypeScript, you can directly use this package instead of hard-coding the below values:
import {
EVENT_TABLE_PK, // => aggregateId
EVENT_TABLE_SK, // => version
EVENT_TABLE_INITIAL_EVENT_INDEX_NAME, // => initialEvents
EVENT_TABLE_IS_INITIAL_EVENT_KEY, // => isInitialEvent
EVENT_TABLE_TIMESTAMP_KEY, // => timestamp
} from '@castore/dynamodb-event-storage-adapter';
CloudFormation
{
"Type": "AWS::DynamoDB::Table",
"Properties": {
"AttributeDefinitions": [
{ "AttributeName": "aggregateId", "AttributeType": "S" },
{ "AttributeName": "version", "AttributeType": "N" }
{ "AttributeName": "isInitialEvent", "AttributeType": "N" },
{ "AttributeName": "timestamp", "AttributeType": "S" }
],
"KeySchema": [
{ "AttributeName": "aggregateId", "KeyType": "HASH" },
{ "AttributeName": "version", "KeyType": "RANGE" }
],
"GlobalSecondaryIndexes": [
{
"IndexName": "initialEvents",
"KeySchema": [
{ "AttributeName": "isInitialEvent", "KeyType": "HASH" },
{ "AttributeName": "timestamp", "KeyType": "RANGE" }
],
"Projection": "KEYS_ONLY"
}
]
}
}
CDK
import { Table, AttributeType, ProjectionType } from 'aws-cdk-lib/aws-dynamodb';
const { STRING, NUMBER } = AttributeType;
const { KEYS_ONLY } = ProjectionType;
const pokemonsEventsTable = new Table(scope, 'PokemonEvents', {
partitionKey: {
name: 'aggregateId',
type: STRING,
},
sortKey: {
name: 'version',
type: NUMBER,
},
});
pokemonsEventsTable.addGlobalSecondaryIndex({
indexName: 'initialEvents',
partitionKey: {
name: 'isInitialEvent',
type: NUMBER,
},
sortKey: {
name: 'timestamp',
type: STRING,
},
projectionType: KEYS_ONLY,
});
Terraform
resource "aws_dynamodb_table" "pokemons-events-table" {
hash_key = "aggregateId"
range_key = "version"
attribute {
name = "aggregateId"
type = "S"
}
attribute {
name = "version"
type = "N"
}
attribute {
name = "isInitialEvent"
type = "N"
}
attribute {
name = "timestamp"
type = "S"
}
global_secondary_index {
name = "initialEvents"
hash_key = "isInitialEvent"
range_key = "timestamp"
projection_type = "KEYS_ONLY"
}
}
🤝 EventGroups
This adapter implements the EventGroups API using the DynamoDb Transactions API:
import { EventStore } from '@castore/core';
// 👇 TransactWriteItems N events simultaneously
await EventStore.pushEventGroup(
// events are correctly typed 🙌
eventStoreA.groupEvent(eventA1),
eventStoreA.groupEvent(eventA2),
eventStoreB.groupEvent(eventB),
...
);
Note that:
- All the event stores involved in the transaction need to use the
DynamoDbEventStorageAdapter
- This util inherits of the
TransactWriteItem
API limitations: It can target up to 100 distinct events in one or more DynamoDB tables within the same AWS account and in the same Region.
🔑 IAM
Required IAM permissions for each operations:
getEvents
(+getAggregate
,getExistingAggregate
):dynamodb:Query
pushEvent
:dynamodb:PutItem
listAggregateIds
:dynamodb:Query
on theinitialEvents
index