readme.md

DynamoTypes

Typescript ORM of DynamoDB, written from scratch to fully support DynamoDB. Powering Vingle

Features

1. Serialize / Deserialize DynamoDB record -> TS class object based on annotations.
2. Table Configurations
   • CreateTable
     • Create secondary indexes (Both local / global)
     • Configure TTL
   • DropTable
3. PrimaryKey
   • FullPrimaryKey (Hash, Range)
   • HashPrimaryKey (Hash)
4. Indexes
   • Local, both hash and range key
   • Global, both hash and range key
5. Attribute
   • Type Support (Number / String / Boolean / Array / Object / Buffer)
   • TimeToLive
6. DAX Support
   • You can specify this by setting the connection of table.
7. Optimized aws-sdk usage
   • aws-sdk has a serious problem of not reusing HTTP connection towards DynamoDB by default. check this issue
   • this could cause unbearable latency sometimes with showing > 100ms. it's more of an issue of NodeJS HTTP module but nevertheless, it has been optimized here by keep-alive Code
8. AWS X-Ray support
   • XRay is serverless distributed tracing service. In order to log DynamoDB transaction into it, you also need to some sort of risk monkey-patching. Here you can turn it on by setting process.env.ENABLE_XRAY = "true"
9. Testing
   • You can change the endpoint of DynamoDB by setting the environment variable or setting new connection, So you can install local-dynamo locally at setup endpoint to local. refer package.json for the detailed how-to

Also, dynamo-types let you overcome several limits that DynamoDB or the aws-sdk has.

1. BatchWrite (batchDelete / batchPut) has a limit of a maximum of 25 items per request.
   • dynamo-types automatically splits given items into chunks of 25 and sends requests in parallel
2. BatchGet has a limit of a maximum of 100 items per requests
   • dynamo-types automatically splits given keys to chunks of 100 and sends requests in parallel
3. BatchGet doesn't keep the order of items as it is in input keys,
   • dynamo-types sort return items based on input keys
4. BatchGet doesn't handle "missing items".
   • dynamo-types has "BatchGet" / "BatchGetFull"
     • BatchGet
       order items follow to keys, missing items are just missing. return type Promise<Array>
       so keys.legnth !== items.keys in this case
     • BatchGetFull
       order items follow to keys, fill missing items with "null". return type Promise<Array<Item | null>>
       so keys.length === items.keys always true

And most importantly, all of those queries regardless of whether it's from index or primary key, strongly typed. I mean what's the point of using typescript if not anyway?

Usage

  @Decorator.Table({ name: "prod-Card" })
  class Card extends Table {
    @Decorator.Attribute()
    public id: number;

    @Decorator.Attribute()
    public title: string;

    @Decorator.Attribute({ timeToLive: true })
    public expiresAt: number;

    @Decorator.FullPrimaryKey('id', 'title')
    static readonly primaryKey: Query.FullPrimaryKey<Card, number, string>;

    @Decorator.Writer()
    static readonly writer: Query.Writer<Card>;
  }

  // Create Table At DynamoDB
  await Card.createTable();

  // Drop Table At DynamoDB
  await Card.dropTable();


  // Creating Record
  const card = new Card();
  card.id = 100;
  card.title = "Title";
  //
  await Card.writer.put(card);
  // OR just
  await card.save();

  // Batch Put
  await Card.writer.batchPut([
    new Card(),
    new Card()
  ]);

  // Get Record
  await Card.primaryKey.get(100, "Title");

  // BatchGet
  // This array is strongly typed such as Array<[number, string]> so don't worry.
  await Card.primaryKey.batchGet([
    [100, "Title"],
    [200, "Title2"]
  ])

  // Query
  // Range key opreations are stringly typed. ([">=", T] | ["=", T] ...)
  await Card.primaryKey.query({
    hash: 100,
    range: [">=", "Title"]
  })

  // Delete record
  await card.delete()

  // Delete record only when it meets condition.
  // with this, you can avoid race condition such as somebody updating the record while you're trying to delete it
  await card.delete({
    condition: { title: Equal("Title") }
  });
  // when mismatch occurs, it raises "ConditionalCheckFailedException" error.

  // Likewise, update record only when it meets condition
  card.title = "New Title"
  await card.save({ condition: { title: "Title" } });
  // when mismatch occurs, it raises "ConditionalCheckFailedException" error.

import {
  Config,
  Decorator,
  Query,
  Table,
} from "dynamo-types";

@Decorator.Table({ name: `table_name` })
export class CardStat extends Table {
  @Decorator.HashPrimaryKey("card_id")
  public static readonly primaryKey: Query.HashPrimaryKey<CardStat, number>;

  @Decorator.Writer()
  public static readonly writer: Query.Writer<CardStat>;

  @Decorator.Attribute({ name: "card_id" })
  public cardId: number;

  @Decorator.Attribute({ name: "impressions_count" })
  public impressionsCount: number = 0;

  @Decorator.Attribute({ name: "shares" })
  public shares: number = 0;
}

TS Compiler Setting

DynamoTypes utilize reflect-metadata to read metadata (usually type of variables) from Typescript code. to do so, you must enable those options.

{
    "compilerOptions": {
        // other options..
        //
        "experimentalDecorators": true, // required
        "emitDecoratorMetadata": true // required
    }
}

Connection

DynamoDB supports 2 different kinds of connections. Plain connections to DynamoDB through HTTP, or through DAX. dynamo-types supports this by letting you create a separate connection for each table.

@Decorator.Table({ name: "prod-Card1", connection: new DAXConnection({ endpoints: ["dax-domain:8892"] }) })
class Card extends Table {
  @AttributeDecorator()
  public id: number;

  @AttributeDecorator()
  public title: string;

  @AttributeDecorator({ name: "complicated_field"})
  public complicatedField: string;

  @FullPrimaryKeyDecorator('id', 'title')
  static readonly primaryKey: Query.FullPrimaryKey<Card, number, string>;

  @WriterDecorator()
  static readonly writer: Query.Writer<Card>;
}

Then any query that is sent to the Card table will be sent through DAXConnection.

If you don't specify any connection, it automatically uses default connection, which is DynamoDBConnection.