An example deploying a Chord-based distributed hash table with Disnix
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README.md

disnix-chord-example

A public Disnix example deploying a Distributed Hash Table (DHT) consisting of a network of Chord nodes. It has been based on OpenChord.

Usage

There are three ways to try to deploy this example.

The deployment/DistributedDeployment folder contains all neccessary Disnix models, such as a services, infrastructure and distribution models required for deployment.

Deployment using Disnix in a heterogeneous network

For this scenario only installation of the basic Disnix toolset is required.

First, you must manually install a network of machines running the Disnix service. Then you must adapt the infrastructure model to match to properties of your network and the distribution model to map the services to the right machines.

We can deploy the system by running the following command:

$ disnix-env -s services.nix -i infrastructure.nix -d distribution.nix

Hybrid deployment of NixOS infrastructure and services using DisnixOS

For this scenario you need to install a network of NixOS machines, running the Disnix service. This can be done by enabling the following configuration option in each /etc/nixos/configuration.nix file:

$ services.disnix.enable = true;

You may also need to adapt the NixOS configurations to which the network.nix model is referring, so that they will match the actual system configurations.

The system including its underlying infrastructure can be deployed by using the disnixos-env command:

$ disnixos-env -s services.nix -n network.nix -d distribution.nix

Deployment using the NixOS test driver

This system can be deployed without adapting any of the models in deployment/DistributedDeployment. By running the following instruction, the system can be deployed in a network of virtual machines:

$ disnixos-vm-env -s services.nix -n network.nix -d distribution.nix

The disadvantage of using the virtualization extension is that no upgrades can be performed and thus the locking mechanism cannot be used.

Deployment using NixOps for infrastructure and Disnix for service deployment

It's also possible to use NixOps for deploying the infrastructure (machines) and let Disnix do the deployment of the services to these machines.

A virtualbox network can be deployed as follows:

$ nixops create ./network.nix ./network-virtualbox.nix -d vboxtest
$ nixops deploy -d vboxtest

The system can be deployed as follows:

$ disnixos-env -s services.nix -n network.nix -d distribution.nix --use-nixops

Testing

To test the Chord network, you can connect to any machine in the network, e.g. through NixOps or a "plain" SSH connection:

$ nixops ssh -d vbox test1

Start the OpenChord console by running the following command:

$ /nix/var/nix/profiles/disnix/default/bin/openchord-console

We can join any Chord node deployed by Disnix as a bootstrap node:

> joinN -port 9000 -bootstrap localhost:8001

We can see the references as follows:

> refsN

The above command shows you one predecessor and all the successors of the current node in the ring.

We can also add an object to the distributed hash table and view the table's content:

> insertN -key test -value test
> entriesN

For more details on how to use the console, consult the OpenChord manual that comes with the package:

$ nix-build deployment/top-level/all-packages.nix -A openchord
$ okular result/share/doc/openchord/manual/manual.pdf

License

The ChordServer package uses the OpenChord API that is GPLv2 licensed. As a result, the ChordServer package that can be found in the src/ folder is covered by the same license. See the license header in the Java class for more information.

The remainder of this repository is MIT licensed.