NestJS Config AWS Parameter Store

This package allows you to configure your NestJS application by loading the configuration from AWS SSM Parameter Store.

Installation

npm install nestjs-param-store @aws-sdk/client-ssm

Configuration

Static configuration

import { Module } from '@nestjs/common';
import { PSConfigModule } from 'nestjs-param-store';

@Module({
  imports: [
    PSConfigModule.register({
      ssmParamStorePath: '/production/services/my-service',
      ssmDecryptParams: true,
      ssmRecursive: false,
      ssmClientOptions: {
        region: 'us-east-1',
      },
    }),
  ],
})
export class AppModule {}

By calling PSConfigModule.register, you configure the module to load all the parameters under the path ssmParamStorePath.

Async configuration

The following example shows how to retrieve the configuration before registering the module.

import { Module } from '@nestjs/common';
import { ConfigModule, ConfigService } from '@nestjs/config';
import { PSConfigModule } from 'nestjs-param-store';

@Module({
  imports: [
    PSConfigModule.registerAsync({
      imports: [ConfigModule],
      useFactory: async (config: ConfigService<EnvironmentVariables>) => ({
        ssmParamStorePath: config.get<string>('APP_CONFIG_PATH'),
        ssmDecryptParams: true,
        ssmRecursive: false,
        ssmClientOptions: {
          region: config.get<string>('AWS_REGION'),
        },
      }),
      inject: [ConfigService],
    }),
  ],
})
export class AppModule {}

Options

Option	Required	Default	Description
ssmParamStorePath	Yes		The hierarchy for the parameter
ssmDecryptParams	No	false	Retrieve all parameters in a hierarchy with their value decrypted
ssmRecursive	No	false	Retrieve all parameters within a hierarchy
ssmClientOptions	No	undefined	Options to pass to the underlying SSM client

Services

This module exposes the following services.

ConfigService

The PSConfigService service allows you to access the configuration loaded from Parameter Store. Use its own class name as the injection token.

Let's assume the following parameters were previously registered:

• /production/services/my-service/pagination-limit: '25'
• /production/services/my-service/post-table: 'ProductionPostTable'

Configure the module with ssmParamStorePath pointing to /production/services/my-service to access all the parameters register for the service in production.

Then, access the configuration as follows:

import { Injectable } from '@nestjs/common';
import { PSConfigService } from 'nestjs-param-store';
import { DynamoDBClient, QueryCommand, GetItemCommand } from '@aws-sdk/client-dynamodb';

@Injectable()
export class PostRepository {
  // Some common initialization.
  public constructor(
    private readonly dynamodbClient: DynamoDBClient,
    private readonly psConfigService: PSConfigService,
  ) {}

  public getPostsByUser(userId: string) {
    // Here: Note how to retrieve the configuration.
    const table = await this.psConfigService.get<string>('post-table');
    const limit = await this.psConfigService.get<number>('pagination-limit');

    const queryCommand = new QueryCommand({
      TableName: table, // <- use
      KeyConditionExpression: 'PK = :pk',
      ExpressionAttributeValues: {
        ':pk': { S: `USER#${userId}` },
      },
      Limit: limit,  // <- use
    });

    const { Items = [] } = await this.dynamodbClient.send(queryCommand);
    // .... snip ....
  }
}

The PSConfigService service exposes the following methods:

• get(name, defaultValue): To retrieve a string configuration.
• getBool(name, defaultValue): To retrieve a boolean configuration. The following values as considered truly: true, True, 1, y, yes, and Yes.
• getNumber(name, defaultValue): To retrieve a numeric configuration.

How does the PSConfigService service resolve the configurations?

When calling get, getBool, or getNumber, the service will look up a parameter whose name ends with the name specified. This means that the match is partial.

Given the following parameter:

• /production/services/my-service/pagination-limit: '25'

It can be retrieved using one of these alternatives:

• get('pagination-limit')
• get('my-service/pagination-limit')
• get('services/my-service/pagination-limit')
• get('production/services/my-service/pagination-limit')

Raw Parameters

You can access the raw parameters loaded from the Parameter Store.

import { Inject, Injectable } from '@nestjs/common';
import { PS_CONFIG_PARAMETERS, PSConfigParameters } from 'nestjs-param-store';

@Injectable()
export class SophisticatedService {
  public constructor(
    @Inject(PS_CONFIG_PARAMETERS) parameters: PSConfigParameters,
  ) {
    console.log(parameters);
  }
}

Example of output:

[
  {
      "Name": "/production/services/my-service/pagination-limit",
      "Type": "String",
      "Value": "25",
      "Version": 1,
      "LastModifiedDate": "2022-09-03T02:55:00.389000-04:00",
      "ARN": "arn:aws:ssm:us-east-1:000000000000:parameter/production/services/my-service/pagination-limit",
      "DataType": "text"
  },
  {
      "Name": "/production/services/my-service/post-table",
      "Type": "String",
      "Value": "ProductionPostTable",
      "Version": 1,
      "LastModifiedDate": "2022-09-03T03:15:15.032000-04:00",
      "ARN": "arn:aws:ssm:us-east-1:000000000000:parameter/production/services/my-service/post-table",
      "DataType": "text"
  }
]

Troubleshooting

Empty list of parameters returned

This happens when recursive is false and the specified path does not resolve the final level in the hierarchy.

Reference: GetParametersByPath

import { Module } from '@nestjs/common';
import { PSConfigModule } from 'nestjs-param-store';

@Module({
  imports: [
    PSConfigModule.register({
      ssmParamStorePath: '/production',
      ssmRecursive: true,   // <-- specify recursively
    }),
  ],
})
export class AppModule {}