CAP Node.js Community Common

Getting Started

• Run npm add @cap-js-community/common in @sap/cds project

About this Project

This project provides common functionality for CDS services to be consumed with SAP Cloud Application Programming Model (Node.js).

Table of Contents

• Replication Cache
• Migration Check
• Rate Limiting
• Redis Client
• Support, Feedback, Contributing
• Code of Conduct
• Licensing

Replication Cache

The replication cache allows to cache a service (e.g. db service) into a tenant-aware SQLite database. Local replicated SQLite database can be queried with same query as the original service.

Usage

@cds.replicate
entity Books {
  key ID       : Integer;
      title    : localized String;
      descr    : localized String;
}

Annotations

Annotations can be used to enable replication cache for a service:

• @cds.replicate: Boolean | Object: Enable replication cache for entity
  • @cds.replicate.ttl: Number: Time-To-Live (TTL) of cache entry in milliseconds
  • @cds.replicate.auto: Boolean: Replication is managed automatically
  • @cds.replicate.preload: Boolean: Preload replication for entity
  • @cds.replicate.group: String: Replication group name

Defaults are taken from CDS environment.

Options

Options can be passed to replication cache via CDS environment via cds.replicationCache section:

• plugin: Boolean: Replication cache is activated via CDS plugin for db service. Default is true
• name: String: Service name. Default is "db"
• group: String: Replication group name. Default is "default"
• credentials: Object: SQLite credentials
  • database: String: Database file. Default is ":memory:" and in production: "data.sqlite"
• ttl: Number: Time-To-Live (TTL) of cache entries in milliseconds. Default is 1800000 (30 minutes)
• check: Number: Interval to check size and prune. Default is 60000 (1 minute)
• stats: Number: Interval to log statistics. Default is 300000 (5 minutes)
• size: Number: Maximal cache size in bytes. Default is 10485760 (10 MB) and in production: 104857600 (100 MB)
• chunks: Number: Replication chunk size. Default is 1000
• retries: Number: Replication retries for failed replications. Default is 3
• auto: Boolean: Replication is managed automatically. Default is true
• prune: Boolean: Check and prune directly after replication. Default is true
• validate: Boolean: Validate count of replicated records. Default is true
• deploy: Boolean: Deploy whole schema to allow queries on projections. Default is true
• preload: Boolean: Preload all replication enables entity. Default is false
• wait: Boolean: Delay read query until replication finished. Default is false
• search: Boolean: Search queries are allowed on replication cache. Default is true
• measure: Boolean: Measure and compare replication cache and service query execution. Default is false
• tmpDir: Boolean: Store replication cache file in temporary directory. Default is false
• baseDir: String: Base directory for replication cache files. Default is "temp"

Test

Replication cache is inactive per default for tests (test profile). It can be enabled via CDS env:

{
  "cds": {
    "replicationCache": {
      "[test]": {
        "plugin": true
      }
    }
  }
}

Migration Check

Options

Options can be passed to migration check via CDS environment via cds.migrationCheck section:

• baseDir: String: Specifies the base directory for migration check. Default is "migration-check"
• whitelist: Boolean: Requires to maintain a whitelist for compatible changes. Default is true
• checkMtx: Boolean: Includes CDS MTXS persistence into check. Default is true
• keep: Boolean: Keeps whitelist after update, otherwise whitelist is cleared. Default is false
• freeze: Boolean: Freeze the persistence. Event compatible changes are not allowed, Default is false
• label: String: Label to describe the updated hash files in addition to the timestamp. Default is ""
• buildPath: String: Path to the build CSN. If not specified it derived from CAP project type. Default is null
• adminHash: String: Specify admin hash to acknowledge incompatible changes. Default is null

Usage

Basic Flow

• Build CSN: cds build --production
• Check migrations: cdsmc
• Update Production CSN: cdsmc -u

Whitelisting

• Maintain the whitelist extension file migration-extension-whitelist.json for compatible changes:
  • Whitelist Entity:

  {
    "definitions": {
      "test.Test": {}
    }
  }

  • Whitelist Entity Element:

  {
    "definitions": {
      "test.Test": {
        "elements": {
          "value": {}
        }
      }
    }
  }

Admin Mode

• Get Admin Hash: cdsmc -a
• (Un-)Freeze Persistence (based on options): cdsmc -u -a

Pipeline

• Build & Check: cds build --production && cdsmc
• Update Production CSN: cdsmc -u

Production CSN MUST be added to version control

Rate Limiting

Usage

@cds.rateLimiting
service BookshopService {
  entity Books @readonly   as projection on test.Books;
}

Annotations

• @cds.rateLimiting: Boolean: Activate rate limit for service
• @cds.rateLimiting.maxConcurrent: Number: Maximum number of concurrent requests per service and tenant
• @cds.rateLimiting.maxInWindow: Number: Maximum number of requests in defined window per service and tenant
• @cds.rateLimiting.window: Number: Window length in milliseconds

Options

Options can be passed to migration check via CDS environment via cds.rateLimiting section:

• plugin: Boolean: Rate limiting is activated via CDS plugin for annotated services. Default is true
• maxConcurrent: Boolean: Maximum number of concurrent requests per service and tenant. Default is 3
• maxWindow: Boolean: Maximum number of requests in defined window per service and tenant. Default is 10000 (10 seconds)
• window: Boolean: Window length in milliseconds. Default is 3600000 (1 hour)
• retry: Boolean: Default is 5

Redis

Redis options can be provided in CDS env as follows:

{
  "cds": {
    "requires": {
      "redis-rateLimiting": {
        "vcap": {
          "tag": "my-redis"
        },
        "options": {}
      }
    }
  }
}

For shared redis configuration Redis service name can be provided in CDS env as follows:

{
  "cds": {
    "requires": {
      "redis-rateLimiting": false,
      "redis": {
        "vcap": {
          "tag": "my-redis"
        },
        "options": {}
      }
    }
  }
}

Test

Rate limiting is inactive per default for tests (test profile). It can be enabled via CDS env:

{
  "cds": {
    "rateLimiting": {
      "[test]": {
        "plugin": true
      }
    }
  }
}

Redis Client

A Redis Client broker is provided to connect to Redis service.

Usage

Main default singleton

const { RedisClient } = require("@cap-js-community/common");
const mainClient = await RedisClient.default().createMainClientAndConnect(options);

Main named singleton

const { RedisClient } = require("@cap-js-community/common");
const mainClient = await RedisClient.default("name").createMainClientAndConnect(options);

Custom named

const { RedisClient } = require("@cap-js-community/common");
const client = await new RedisClient("name").createClientAndConnect(options);

Options

Options can be passed to Redis client via CDS environment via cds.redis section: Redis options can be provided in CDS env as follows:

{
  "cds": {
    "requires": {
      "redis": {
        "vcap": {
          "tag": "redis-cache"
        },
        "options": {}
      }
    }
  }
}

Specific Redis options for a custom name can be established as follows:

{
  "cds": {
    "requires": {
      "redis-customName": {
        "vcap": {
          "tag": "redis-cache"
        },
        "options": {}
      }
    }
  }
}

const { RedisClient } = require("@cap-js-community/common");
const mainClient = await RedisClient.default("customName").createMainClientAndConnect(options);

In addition, options can be passed to Redis client during creation via options parameter:

const { RedisClient } = require("@cap-js-community/common");
const mainClient = await RedisClient.default().createMainClientAndConnect(options);

For details on Redis createClient configuration options see Redis Client Configuration.

Support, Feedback, Contributing

This project is open to feature requests/suggestions, bug reports etc. via GitHub issues. Contribution and feedback are encouraged and always welcome. For more information about how to contribute, the project structure, as well as additional contribution information, see our Contribution Guidelines.

Code of Conduct

We as members, contributors, and leaders pledge to make participation in our community a harassment-free experience for everyone. By participating in this project, you agree to abide by its Code of Conduct at all times.

Licensing

Copyright 2025 SAP SE or an SAP affiliate company and common contributors. Please see our LICENSE for copyright and license information. Detailed information including third-party components and their licensing/copyright information is available via the REUSE tool.