Omen

Omen is a distributed data system, running within your load-balanced Node.js service. It has redundant caching and storage, with hash ring orchestration, eventual consistency and latency-optimized routing.

Advantages

• Omen is part of your application. It frees you from installing, configuring and connecting to multiple data services.

• Omen uses the very stable and fast LevelDB database via the leveldown module for disk persistence.

• Modern web services have features such as load balancing, multi-region deployment, process management, monitoring, auto scaling, continuous integration and more. Omen is part of your service, so it gets your service's operational features for free.

• Omen is crazy fast, because:

  • Peers measure latency and use the fastest routes.
  • One ring handles caching and storage, so network requests are reduced.
  • In-process objects can be modified without deserialization.
  • Requests can route internally because clients can also be peers.
  • Frequently-written data can be pre-aggregated locally.
  • Frequently-accessed data can be cached globally.

Install Omen

npm install --save omen

Use Omen

var server = require('za')().listen(8888);

var ring = require('omen')({
  hostPattern: 'app-(eu|use|usw|apn)-(1-5).lighter.io'
});

ring.set('foo', 'bar', function (err) {
  ring.get('foo', function (foo) {
    process.assert(foo == 'bar');
  });
});

omen([options])

The omen library outputs a ring object on which ring methods are called. A ring object is created with several options that govern the ring's bootstrapping and behavior.

options.processCount

The process count specifies the number of CPUs per host, and it defaults to using all available CPUs.

options.dataLocation

The database path is where LevelDB data is stored, with a subdirectory for each worker. The default path is the data directory in the current working directory.

options.replicas

The replicas setting indicates the number of times to replicate a key-value pair around the ring for redundancy. This number includes the main entry as well as duplicates, so it must be at least 1, and the default is 5.

options.cacheSize

The cache size indicates the number of items to keep in LRU cache, with the default being 10,000.

options.basePort

The base port is the first port on which processes will listen, with each subsequent process incrementing that number by 1. The default is 12300. So if a host has 4 processes and uses the default basePort, it will listen on ports 12300, 12301, 12302 and 12303.

options.hostPattern

The host pattern is used to bootstrap the host discovery process. It defaults to the current hostname, so it must be set in order to allow multiple hosts to interact.

The pattern supports parenthetical expressions which can be pipe-delimited lists or a start and end number for a sequence. So if you had 10 hosts across 2 US locales, your host pattern might look like: "omen-us(east|west)-(1-5).domain.tld".

options.isClientOnly (Default: false)

If the current process needs to access the ring, but will not store data as a peer, it should set isClientOnly to true. The default is false.

options.pingDelay (Default: 1e3)

The ping delay is the number of milliseconds a peer waits between attempts to discover all peers or heartbeats to a peer to verify the connection and to measure latency. The default is 1,000 (one second).

options.log

Omen can use a custom log. The default is console.

ring

ring.increment(key[, path, number, fn])

ring.on()

Acknowledgements

We would like to thank all of the amazing people who use, support, promote, enhance, document, patch, and submit comments & issues. Omen couldn't exist without you.

We depend on leveldown, so thanks are due to Rod Vagg, and everyone who contributes to LevelDB and related modules.

Additionally, huge thanks go to Goin’ for employing and supporting Omen project maintainers, and for being an epically awesome place to work (and play).

MIT License

Copyright (c) 2014 Sam Eubank

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

How to Contribute

We welcome contributions from the community and are happy to have them. Please follow this guide when logging issues or making code changes.

Logging Issues

All issues should be created using the new issue form. Please describe the issue including steps to reproduce. Also, make sure to indicate the version that has the issue.

Changing Code

Code changes are welcome and encouraged! Please follow our process:

1. Fork the repository on GitHub.
2. Fix the issue ensuring that your code follows the style guide.
3. Add tests for your new code, ensuring that you have 100% code coverage. (If necessary, we can help you reach 100% prior to merging.)
   • Run npm test to run tests quickly, without testing coverage.
   • Run npm run cover to test coverage and generate a report.
   • Run npm run report to open the coverage report you generated.
4. Pull requests should be made to the master branch.

Contributor Code of Conduct

As contributors and maintainers of Omen, we pledge to respect all people who contribute through reporting issues, posting feature requests, updating documentation, submitting pull requests or patches, and other activities.

If any participant in this project has issues or takes exception with a contribution, they are obligated to provide constructive feedback and never resort to personal attacks, trolling, public or private harassment, insults, or other unprofessional conduct.

Project maintainers have the right and responsibility to remove, edit, or reject comments, commits, code, edits, issues, and other contributions that are not aligned with this Code of Conduct. Project maintainers who do not follow the Code of Conduct may be removed from the project team.

Instances of abusive, harassing, or otherwise unacceptable behavior may be reported by opening an issue or contacting one or more of the project maintainers.

We promise to extend courtesy and respect to everyone involved in this project regardless of gender, gender identity, sexual orientation, ability or disability, ethnicity, religion, age, location, native language, or level of experience.