deferred-leveldown

What is deferred-leveldown?

The deferred-leveldown npm package is a wrapper for LevelDOWN that defers operations until the underlying store is ready. This is particularly useful for scenarios where you need to queue operations while waiting for the database to be initialized or opened.

What are deferred-leveldown's main functionalities?

Deferred Operations

This feature allows you to queue operations like 'put' and 'get' until the underlying LevelDOWN store is ready. The operations will be executed once the store is initialized.

const levelup = require('levelup');
const leveldown = require('leveldown');
const deferredLeveldown = require('deferred-leveldown');

const db = levelup(deferredLeveldown(leveldown('./mydb')));

db.put('key', 'value', (err) => {
  if (err) return console.error('Error:', err);
  console.log('Put operation completed');
});

db.get('key', (err, value) => {
  if (err) return console.error('Error:', err);
  console.log('Got value:', value);
});

Error Handling

This feature demonstrates how deferred-leveldown handles errors. If an operation fails, the error is passed to the callback, allowing you to handle it appropriately.

const levelup = require('levelup');
const leveldown = require('leveldown');
const deferredLeveldown = require('deferred-leveldown');

const db = levelup(deferredLeveldown(leveldown('./mydb')));

db.put('key', 'value', (err) => {
  if (err) return console.error('Error:', err);
  console.log('Put operation completed');
});

db.get('nonexistentKey', (err, value) => {
  if (err) return console.error('Error:', err);
  console.log('Got value:', value);
});

Other packages similar to deferred-leveldown

levelup

LevelUP is a higher-level module for working with LevelDB, providing a more user-friendly API. Unlike deferred-leveldown, LevelUP does not defer operations but can be used in conjunction with deferred-leveldown to achieve similar functionality.

subleveldown

SublevelDOWN is a package that provides namespaced sublevels for LevelDB. It allows you to create isolated sub-databases within a LevelDB instance. While it does not defer operations, it can be used alongside deferred-leveldown for more complex database structures.

memdown

MemDOWN is an in-memory backend for LevelUP, useful for testing and temporary data storage. It does not provide deferred operations but can be used as a fast, in-memory alternative to LevelDOWN.

README

DeferredLevelDOWN

A mock LevelDOWN implementation that queues operations while a real LevelDOWN instance is being opened.

DeferredLevelDOWN implements the basic AbstractLevelDOWN API so it can be used as a drop-in replacement where LevelDOWN is needed.

put(), get(), del() and batch() operations are all queued and kept in memory until a new LevelDOWN-compatible object can be supplied.

The setDb(db) method is used to supply a new LevelDOWN object. Once received, all queued operations are replayed against that object, in order.

batch() operations will all be replayed as the array form. Chained-batch operations are converted before being stored.

Contributing

DeferredLevelDOWN is an OPEN Open Source Project. This means that:

Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit. This project is more like an open wiki than a standard guarded open source project.

See the CONTRIBUTING.md file for more details.

Contributors

DeferredLevelDOWN is only possible due to the excellent work of the following contributors:

Rod Vagg	GitHub/rvagg	Twitter/@rvagg
John Chesley	GitHub/chesles	Twitter/@chesles
Jake Verbaten	GitHub/raynos	Twitter/@raynos2
Dominic Tarr	GitHub/dominictarr	Twitter/@dominictarr
Max Ogden	GitHub/maxogden	Twitter/@maxogden
Lars-Magnus Skog	GitHub/ralphtheninja	Twitter/@ralphtheninja
David Björklund	GitHub/kesla	Twitter/@david_bjorklund
Julian Gruber	GitHub/juliangruber	Twitter/@juliangruber
Paolo Fragomeni	GitHub/hij1nx	Twitter/@hij1nx
Anton Whalley	GitHub/No9	Twitter/@antonwhalley
Matteo Collina	GitHub/mcollina	Twitter/@matteocollina
Pedro Teixeira	GitHub/pgte	Twitter/@pgte
James Halliday	GitHub/substack	Twitter/@substack

License & copyright

Copyright (c) 2013-2015 DeferredLevelDOWN contributors (listed above).

DeferredLevelDOWN is licensed under the MIT license. All rights not explicitly granted in the MIT license are reserved. See the included LICENSE.md file for more details.

Changelog

[1.0.0] - 2015-04-28

Changed

• Upgrade to abstract-leveldown@2.1.2 (@ralphtheninja)