|
| 1 | +# DynamoDB Client Utilities |
| 2 | + |
| 3 | +The DynamoDB client utilities provide reusable singleton instances of `DynamoDBClient` and `DynamoDBDocumentClient` for use in AWS Lambda functions. These utilities enable you to configure clients once and reuse them across invocations, following AWS best practices for Lambda performance optimization. |
| 4 | + |
| 5 | +## Overview |
| 6 | + |
| 7 | +The utility exports the following functions: |
| 8 | + |
| 9 | +- `initializeDynamoDBClients()` - Initialize both DynamoDB clients with optional configuration |
| 10 | +- `getDynamoDBClient()` - Get the singleton DynamoDB client instance |
| 11 | +- `getDynamoDBDocumentClient()` - Get the singleton DynamoDB Document client instance |
| 12 | +- `resetDynamoDBClients()` - Reset both client instances (useful for testing) |
| 13 | + |
| 14 | +## Usage |
| 15 | + |
| 16 | +### Basic Usage |
| 17 | + |
| 18 | +```typescript |
| 19 | +import { initializeDynamoDBClients, getDynamoDBDocumentClient } from '@leanstacks/lambda-utils'; |
| 20 | +import { PutCommand } from '@aws-sdk/lib-dynamodb'; |
| 21 | + |
| 22 | +// Initialize both clients (typically done once outside the handler) |
| 23 | +initializeDynamoDBClients({ region: 'us-east-1' }); |
| 24 | + |
| 25 | +export const handler = async (event: any) => { |
| 26 | + // Get the document client (most common use case) |
| 27 | + const docClient = getDynamoDBDocumentClient(); |
| 28 | + |
| 29 | + // Use the document client |
| 30 | + await docClient.send( |
| 31 | + new PutCommand({ |
| 32 | + TableName: 'MyTable', |
| 33 | + Item: { id: '123', name: 'Example' }, |
| 34 | + }), |
| 35 | + ); |
| 36 | +}; |
| 37 | +``` |
| 38 | + |
| 39 | +### Using the Base DynamoDB Client |
| 40 | + |
| 41 | +````typescript |
| 42 | +import { initializeDynamoDBClients, getDynamoDBClient } from '@leanstacks/lambda-utils'; |
| 43 | +import { PutItemCommand } from '@aws-sdk/client-dynamodb'; |
| 44 | + |
| 45 | +// Initialize both clients |
| 46 | +initializeDynamoDBClients({ region: 'us-east-1' }); |
| 47 | + |
| 48 | +export const handler = async (event: any) => { |
| 49 | + // Get the base client for advanced use cases |
| 50 | + const client = getDynamoDBClient(); |
| 51 | + |
| 52 | + // Use the base client |
| 53 | + await client.send(new PutItemCommand({ |
| 54 | + TableName: 'MyTable', |
| 55 | + Item: { id: { S: '123' }, name: { S: 'Example' } } |
| 56 | + })); |
| 57 | + |
| 58 | +### Advanced Configuration |
| 59 | + |
| 60 | +#### Custom DynamoDB Client Configuration |
| 61 | + |
| 62 | +```typescript |
| 63 | +import { initializeDynamoDBClients } from '@leanstacks/lambda-utils'; |
| 64 | +
|
| 65 | +initializeDynamoDBClients({ |
| 66 | + region: 'us-west-2', |
| 67 | + endpoint: 'http://localhost:8000', // For local development |
| 68 | + credentials: { |
| 69 | + accessKeyId: 'local', |
| 70 | + secretAccessKey: 'local', |
| 71 | + }, |
| 72 | +}); |
| 73 | +```` |
| 74 | +
|
| 75 | +#### Custom Marshall/Unmarshall Options |
| 76 | +
|
| 77 | +```typescript |
| 78 | +import { initializeDynamoDBClients } from '@leanstacks/lambda-utils'; |
| 79 | + |
| 80 | +initializeDynamoDBClients( |
| 81 | + { region: 'us-east-1' }, |
| 82 | + { |
| 83 | + // Marshall options |
| 84 | + removeUndefinedValues: true, |
| 85 | + convertEmptyValues: false, |
| 86 | + convertClassInstanceToMap: true, |
| 87 | + }, |
| 88 | + { |
| 89 | + // Unmarshall options |
| 90 | + wrapNumbers: false, |
| 91 | + }, |
| 92 | +); |
| 93 | +``` |
| 94 | +
|
| 95 | +### Lambda Handler Pattern |
| 96 | +
|
| 97 | +```typescript |
| 98 | +import { initializeDynamoDBClients, getDynamoDBDocumentClient } from '@leanstacks/lambda-utils'; |
| 99 | +import { GetCommand } from '@aws-sdk/lib-dynamodb'; |
| 100 | + |
| 101 | +// Initialize clients outside the handler (runs once per cold start) |
| 102 | +initializeDynamoDBClients({ region: process.env.AWS_REGION }, { removeUndefinedValues: true }); |
| 103 | + |
| 104 | +// Handler function |
| 105 | +export const handler = async (event: any) => { |
| 106 | + const docClient = getDynamoDBDocumentClient(); |
| 107 | + |
| 108 | + const result = await docClient.send( |
| 109 | + new GetCommand({ |
| 110 | + TableName: process.env.TABLE_NAME, |
| 111 | + Key: { id: event.id }, |
| 112 | + }), |
| 113 | + ); |
| 114 | + |
| 115 | + return result.Item; |
| 116 | +}; |
| 117 | +``` |
| 118 | +
|
| 119 | +## API Reference |
| 120 | +
|
| 121 | +### `initializeDynamoDBClients(config?, marshallOptions?, unmarshallOptions?): { client: DynamoDBClient; documentClient: DynamoDBDocumentClient }` |
| 122 | +
|
| 123 | +Initializes both the DynamoDB client and DynamoDB Document client with the provided configuration. |
| 124 | +
|
| 125 | +**Parameters:** |
| 126 | +
|
| 127 | +- `config` (optional) - DynamoDB client configuration object |
| 128 | +- `marshallOptions` (optional) - Options for marshalling JavaScript objects to DynamoDB AttributeValues |
| 129 | +- `unmarshallOptions` (optional) - Options for unmarshalling DynamoDB AttributeValues to JavaScript objects |
| 130 | +
|
| 131 | +**Returns:** |
| 132 | +
|
| 133 | +- An object containing both `client` (DynamoDBClient) and `documentClient` (DynamoDBDocumentClient) |
| 134 | +
|
| 135 | +**Notes:** |
| 136 | +
|
| 137 | +- Creates both clients in a single call |
| 138 | +- If called multiple times, it will replace the existing client instances |
| 139 | +- If no config is provided, uses default AWS SDK configuration |
| 140 | +- Most users will only need the `documentClient` from the return value or via `getDynamoDBDocumentClient()` |
| 141 | +
|
| 142 | +### `getDynamoDBClient(): DynamoDBClient` |
| 143 | +
|
| 144 | +Returns the singleton DynamoDB client instance. |
| 145 | +
|
| 146 | +**Returns:** |
| 147 | +
|
| 148 | +- The `DynamoDBClient` instance |
| 149 | +
|
| 150 | +**Throws:** |
| 151 | +
|
| 152 | +- Error if the client has not been initialized |
| 153 | +
|
| 154 | +### `getDynamoDBDocumentClient(): DynamoDBDocumentClient` |
| 155 | +
|
| 156 | +Returns the singleton DynamoDB Document client instance. |
| 157 | +
|
| 158 | +**Returns:** |
| 159 | +
|
| 160 | +- The `DynamoDBDocumentClient` instance |
| 161 | +
|
| 162 | +**Throws:** |
| 163 | +
|
| 164 | +- Error if the document client has not been initialized |
| 165 | +
|
| 166 | +### `resetDynamoDBClients(): void` |
| 167 | +
|
| 168 | +Resets both DynamoDB client instances to null. |
| 169 | +
|
| 170 | +**Notes:** |
| 171 | +
|
| 172 | +- Primarily useful for testing scenarios where you need to reinitialize clients with different configurations |
| 173 | +- After calling this, you must reinitialize the clients before using the getter functions |
| 174 | +
|
| 175 | +## Best Practices |
| 176 | +
|
| 177 | +1. **Initialize Outside the Handler**: Always initialize clients outside your Lambda handler function to reuse the instance across invocations. |
| 178 | +
|
| 179 | +2. **Use Environment Variables**: Configure clients using environment variables for flexibility across environments. |
| 180 | +
|
| 181 | +3. **Error Handling**: Always wrap client operations in try-catch blocks to handle errors gracefully. |
| 182 | +
|
| 183 | +4. **Testing**: Use `resetDynamoDBClients()` in test setup/teardown to ensure clean test isolation. |
| 184 | +
|
| 185 | +## Testing Example |
| 186 | +
|
| 187 | +```typescript |
| 188 | +import { initializeDynamoDBClients, getDynamoDBDocumentClient, resetDynamoDBClients } from '@leanstacks/lambda-utils'; |
| 189 | + |
| 190 | +describe('MyLambdaHandler', () => { |
| 191 | + beforeEach(() => { |
| 192 | + resetDynamoDBClients(); |
| 193 | + initializeDynamoDBClients( |
| 194 | + { region: 'us-east-1', endpoint: 'http://localhost:8000' }, |
| 195 | + { removeUndefinedValues: true }, |
| 196 | + ); |
| 197 | + }); |
| 198 | + |
| 199 | + afterEach(() => { |
| 200 | + resetDynamoDBClients(); |
| 201 | + }); |
| 202 | + |
| 203 | + it('should retrieve item from DynamoDB', async () => { |
| 204 | + // Your test code here |
| 205 | + }); |
| 206 | +}); |
| 207 | +``` |
| 208 | +
|
| 209 | +## Related Resources |
| 210 | +
|
| 211 | +- **[AWS SDK for JavaScript v3 - DynamoDB Client](https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/clients/client-dynamodb/)** |
| 212 | +- **[AWS SDK for JavaScript v3 - DynamoDB Document Client](https://docs.aws.amazon.com/AWSJavaScriptSDK/v3/latest/Package/-aws-sdk-lib-dynamodb/Class/DynamoDBDocumentClient/)** |
| 213 | +- **[AWS Lambda Best Practices](https://docs.aws.amazon.com/lambda/latest/dg/best-practices.html)** |
| 214 | +- **[Back to the project documentation](README.md)** |
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