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https://github.com/Level/party
Open a leveldb handle multiple times.
https://github.com/Level/party
level leveldb multileveldown nodejs
Last synced: about 2 months ago
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Open a leveldb handle multiple times.
- Host: GitHub
- URL: https://github.com/Level/party
- Owner: Level
- License: mit
- Created: 2014-02-17T12:21:18.000Z (over 10 years ago)
- Default Branch: master
- Last Pushed: 2023-02-01T22:02:09.000Z (over 1 year ago)
- Last Synced: 2024-04-14T00:38:23.706Z (5 months ago)
- Topics: level, leveldb, multileveldown, nodejs
- Language: JavaScript
- Homepage:
- Size: 60.5 KB
- Stars: 145
- Watchers: 5
- Forks: 13
- Open Issues: 4
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
README
# level-party
Open a leveldb handle multiple times, transparently upgrading to use
[`multileveldown`](https://npmjs.org/package/multileveldown) when more than 1 process try to use the same leveldb data directory at once and re-electing a new master when the primary unix socket goes down.
[![level badge][level-badge]](https://github.com/Level/awesome)
[](https://www.npmjs.com/package/level-party)
[](https://www.npmjs.com/package/level-party)
[](https://github.com/Level/party/actions/workflows/test.yml)
[](https://codecov.io/gh/Level/party)
[](https://standardjs.com)
[](https://common-changelog.org)
[](https://opencollective.com/level)
## Example
Normally with [`level`](https://npmjs.org/package/level), when you try to open
a database handle from more than one process you will get a locking error:
```
events.js:72
throw er; // Unhandled 'error' event
^
OpenError: IO error: lock /home/substack/projects/level-party/example/data/LOCK: Resource temporarily unavailable
at /home/substack/projects/level-party/node_modules/level/node_modules/level-packager/node_modules/levelup/lib/levelup.js:114:34
```
With `level-party`, the database open will automatically drop down to using
multilevel over a unix socket using metadata placed into the level data
directory transparently.
This means that if you have 2 programs, 1 that gets:
```js
const level = require('level-party')
const db = level(__dirname + '/data', { valueEncoding: 'json' })
setInterval(function () {
db.get('a', function (err, value) {
console.log('a=', value)
})
}, 250)
```
And 1 that puts:
```js
const level = require('level-party')
const db = level(__dirname + '/data', { valueEncoding: 'json' })
const n = Math.floor(Math.random() * 100000)
setInterval(function () {
db.put('a', n + 1)
}, 1000)
```
and you start them up in any order, everything will just work! No more
`IO error: lock` exceptions.
```
$ node put.js & sleep 0.2; node put.js & sleep 0.2; node put.js & sleep 0.2; node put.js & sleep 0.2
[1] 3498
[2] 3502
[3] 3509
[4] 3513
$ node get.js
a= 35340
a= 31575
a= 37639
a= 58874
a= 35341
a= 31576
$ node get.js
a= 35344
a= 31579
a= 37643
a= 58878
a= 35345
^C
```
Hooray!
## Seamless failover
level-party does seamless failover. This means that if you create a read-stream
and the leader goes down while you are reading that stream level-party will resume your stream on the new leader.
[**This disables leveldb snapshotting**](https://github.com/level/leveldown#snapshots) so if your app relies on this you should disable this by setting `opts.retry = false`:
```js
const db = level('./data', { retry: false }) // will not retry streams / gets / puts if the leader goes down
```
## Windows support
`level-party` works on Windows as well using named pipes.
## API
### `db = level(...)`
The arguments are exactly the same as [`level`](https://npmjs.org/package/level). You will sometimes get a real leveldb handle and sometimes get a `multileveldown` handle back in the response.
## Install
With [npm](https://npmjs.org) do:
```
npm install level-party
```
## Contributing
[`Level/party`](https://github.com/Level/party) 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 [Contribution Guide](https://github.com/Level/community/blob/master/CONTRIBUTING.md) for more details.
## Donate
Support us with a monthly donation on [Open Collective](https://opencollective.com/level) and help us continue our work.
## License
[MIT](LICENSE)
[level-badge]: https://leveljs.org/img/badge.svg