keydb

KeyDB is generic middleware for data.

KeyDB provides the tools to create somewhat consistent read/write APIs to heterogenous data sources. The key word here is somewhat. KeyDB does not attempt to completely paper over the semantic differences of all possible data sources. Instead, it uses the middleware concept to have low level "sources" that speak the native semantics of a physical data source and higher level "drivers" that massage those semantics into more consistent APIs.

The "key" in KeyDB refers to the desire to use key/value semantics as much as possible for reasons of performance, simplicity, and because it's usually a common denominator across data sources.

An original goal of KeyDB was to provide consistent data APIs across client and server. For example, local storage and MySQL. Currently, the focus is on server APIs, but hopefully the original intent will be revisited in the future.

Installation

npm

npm install keydb

Usage

By default, KeyDB is a middleware stack that does almost nothing. At a minimum, you must provide it with a data source. A data source is just a function that returns data.

var keydb = require('keydb');
 
var db = keydb();
 
db.source(function (msg) {
  return msg;
});
 
db("Hello, World!").then(function (msg) {
  console.log(msg);
});

The above database will simply echo the message sent to it. Note that KeyDB does automatically wrap synchronous data sources in a promise API. This is the default behavior because it is possible to make synchronouse APIs asynchronous, but it is impossible to make asynchronous APIs synchronous. Some drivers take a synchronous option, including the default stack driver. For example:

var keydb = require('keydb');
 
var db = keydb({sync: true});
 
db.source(function (msg) {
  return msg;
});
 
console.log(db("Hello, world"));

Of course, the above data sources aren't very useful. To do something more useful, use the included drivers.

var keydb = require('keydb');
 
var db = keydb();
 
db.driver(keydb.drivers.upsert);
db.driver(keydb.drivers.mysql, {
  database: 'test',
    tables: {
      user: {
        properties: {
          user_id: {
            type: 'string',
            maxLength: 100
          },
          first_name: {
            type: 'string',
            maxLength: 100
          },
          last_name: {
            type: 'string',
            maxLength: 100
          }
        },
        primaryKey: 'user_id'
      }
    }
});
 
db({
    op: 'upsert',
    attributes: {
      user_id: 'joe', first_name: 'Joe', last_name: 'Foo'
    },
    filters: {user_id: 'joe'}
  })
  .then(function () {
    return db({op: 'query', filters: {user_id: 'joe'}});
  })
  .then(function (msg) {
    console.log(msg.items);
  })

In the above example, an upsert driver is stacked on top of a mysql driver so that upsert semantics can be added to mysql without the underlying driver actually supporting upsert. (Of course, MySQL does directly provide some upsert capabilities. Just pretend it doesn't.) This demonstrates the philosophy and use of middleware in KeyDB. Each source and driver does only what it needs to do. Other features are added by stacking drivers together, rather than making monolithic data sources or drivers.

Some drivers are preconfigured stacks, and these can be easily created by their names. They may also add sugar methods.

var keydb = require('keydb');
 
var db = keydb('kv-mysql');
 
db.set('users/joe', {firstName: 'Joe'})
  .then(function () {
    return db.get('users/joe');
  })

The above is the same as:

var keydb = require('keydb');
 
var db = keydb('kv-mysql');
 
db({op: 'set', key: 'users/joe', value: {firstName: 'Joe'}})
  .then(function () {
    return db({op: 'get', key: 'users/joe'});
  })