UeberDB2: Abstract your databases

About

✓ UeberDB turns every database into a simple key value store by providing a layer of abstraction between your software and your database.

✓ UeberDB uses a cache and buffer to make databases faster. Reads are cached and writes are done in a bulk. This can be turned off.

✓ UeberDB does bulk writing ergo reduces the overhead of database transactions.

✓ UeberDB uses a simple and clean syntax ergo getting started is easy.

Database Support

• Couch
• Dirty
• Elasticsearch
• Maria
• MsSQL
• MySQL
• Postgres (single connection and with connection pool)
• Redis
• Rethink
• SQLite

Install

npm install ueberdb2

Examples

Basic

const ueberdb = require('ueberdb2');

// mysql
const db = new ueberdb.Database('mysql', {
  user: 'root',
  host: 'localhost',
  password: '',
  database: 'store',
  engine: 'InnoDB',
});

// dirty to file system
//const db = new ueberdb.Database('dirty', {filename: 'var/dirty.db'});

async function example(db) {
  await db.init();

  // no need for await because it's already in cache.
  db.set('valueA', {a: 1, b: 2});

  db.get('valueA', function (err, value) {
    // close the database connection.
    db.close(function () {
      process.exit(0);
    });
  });
}

example(db);

findKeys

const ueberdb = require('ueberdb2');
const db = new ueberdb.Database('dirty', {filename: 'var/dirty.db'});

async function example(db){
  await db.init();

  // no need for await because it's already in cache.
  db.set('valueA', {a: 1, b: 2});
  db.set('valueA:h1', {a: 1, b: 2});
  db.set('valueA:h2', {a: 3, b: 4});

  db.findKeys('valueA:*', null, function (err, value) { // TODO: Check this
    // value will be ['valueA:h1', 'valueA:h2']
    db.close(function () {
      process.exit(0);
    });
  });
}

example(db);

Getting and setting subkeys

.get is useful for getting

"foo" : {
  ...all of this...
}

.getsub is useful for getting

"foo:bar" : {
  "pads" : {
    ...all of this...
  }
}

setSub sets the subkeys of keys IE

"foo:bar" : {
  "pads" : {
    ...all of this...
  }
}

getSub

key is the key[string] IE "foo:bar" subkey is an array of subkeys you want to get IE ['pads','someothersubkey'];

Example: const result = await db.getSub(key, subkey); // returns an array of responses

setSub

key is the key[string] IE "foo:bar" subkey is an array of subkeys you want to set IE ['pads','someothersubkey']; value is a value[string] to set IE "hello world"

Example: db.setSub(key, subkey, value);

Disable the read cache

Set the cache wrapper option to 0 to force every read operation to go directly to the database driver (except for reads of written values that have not yet been committed to the database):

const ueberdb = require('ueberdb2');

(async () => {
  const db = new ueberdb.Database(
      'dirty', {filename: 'var/dirty.db'}, {cache: 0});
  await db.init();
  db.set('valueA', {a: 1, b: 2});
  db.get('valueA', (err, value) => {
    console.log(JSON.stringify(value));
    db.close(() => {
      process.exit(0);
    });
  });
})();

Disable write buffering

Set the writeInterval wrapper option to 0 to force writes to go directly to the database driver:

const ueberdb = require('ueberdb2');

(async () => {
  const db = new ueberdb.Database(
      'dirty', {filename: 'var/dirty.db'}, {writeInterval: 0});
  await db.init();
  db.set('valueA', {a: 1, b: 2});
  db.get('valueA', (err, value) => {
    console.log(JSON.stringify(value));
    db.close(() => {
      process.exit(0);
    });
  });
})();

Feature support

Limitations

findKeys query support

The following characters should be avoided in keys \^$.|?*+()[{ as they will cause findKeys to fail.

findKeys database support*

The following have limitations on findKeys

• redis (Only keys of the format *:*:*)
• cassandra (Only keys of the format *:*:*)
• elasticsearch (Only keys of the format *:*:*)
• rethink (Currently doesn't work)

For details on how it works please refer to the wiki: https://github.com/ether/UeberDB/wiki/findKeys-functionality

Scaling, High availability and disaster recovery.

To scale UeberDB you should use sharding especially for real time applications. An example of this is sharding given Pads within Etherpad based on their initial pad authors geographical location. High availability and disaster recovery can be provided through replication of your database however YMMV on passing Settings to your database library. Do not be under the illusion that UeberDB provides any Stateless capabilities, it does not. An option is to use something like rethinkdb and set cache to 0 but YMMV.

Key Length Restrictions

Your Key Length will be limited by the database you chose to use but keep into account portability within your application.

doBulk operations on .set out of memory

doBulk operations that chain IE a large number of .set without a pause to handle the channel clearance can cause a Javascript out of heap memory. It's very rare this happens and is usually due to a bug in software causing a constant write to the database.

MySQL /MariaDB Advice

You should create your database as utf8mb4_bin.

Redis TLS communication

If you enabled TLS on your Redis database (available since Redis 6.0) you will need to change your connections parameters, here is an example:

settings:
    {
      host:
      port: rediss://<redis_database_address>:<redis_database_port>
      socket:
      database:
      password:
      client_options
    }

Do not provide a host value.

If you don't provide a certificate on the client side, you need to add the environment variable NODE_TLS_REJECT_UNAUTHORIZED = 0 and add the flag --tls-auth-clients no when launching the redis-server to accept connections.

How to add support for another database

1. Add your database to packages.json, this will happen automatically if you run npm install %yourdatabase%
2. Add some example settings to test/lib/databases.js for your database.
3. Look at databases/mysql_db.js, your module have to provide the same functions. Call it DATABASENAME_db.js and reimplement the functions for your database. Most of your work here will be copy/paste from other databases so don't be scared.
4. Add your database Travis setup steps to .travis.yml, see the before_install section and MySQL example. Note that MySQL has a preloaded script (comes from mysql.sql) which preloads the database with 1M records. If you can, you should do the same.
5. Run npm test and ensure it's working.
6. Branch from master git checkout -b my-awesome-database and submit a pull request including the changes which should include 1 new and 3 modified files.
7. Once merged we really need you to be on top of maintaining your code.

License

Apache License v2

What's changed from UeberDB?

• Dropped broken databases: CrateDB, LevelDB, LMDB, and MongoDB (probably a breaking change for some people)
• Introduced CI.
• Introduced better testing.
• Fixed broken database clients IE Redis.
• Updated Depdendencies where possible.
• Tidied file structure.
• Improved documentation.
• Sensible name for software makes it clear that it's maintained by The Etherpad Foundation.
• Make db.init await / async

Dirty_Git Easter Egg.

• I suck at hiding Easter eggs..

Dirty_git will commit and push to Git on every set. To use git init or git clone within your dirty database location and then set your upstream IE git remote add origin git://whztevz.

The logic behind dirty git is that you can still use dirty but you can also have offsite backups. It's noisy and spammy but it can be useful.