##Introduction Skynet is a communication protocol for building massively distributed apps in Go. It is not constrained to Go, so it will lend itself nicely to polyglot environments. The first planned language addition is Ruby.
##Tell me more: Servers die, stop communicating, catch on fire, get killed by robots from the future, and should not be trusted.
If your site won’t work with a Chaos Monkey, it isn’t safe. Enter Skynet. Each Skynet module is self–contained and self–aware – if you have one server with an authentication module on it, and that server melts, Skynet will notice, kill it, and automatically create a new one. (if you let it)
Skynet probably won’t die unless your data center gets hit by a comet. We recommend at least 2 data centers in that scenario.
Skynet Services are where the work gets done. These are the processes that service the requests, process the API calls, get the external data, log the requests, authenticate the users, etc.
Before you can run skynet you'll need to have at least one doozerd process running.
##How? Each process in SkyNet receives its configuration from a centralized configuration repository (currently Doozer - possibly pluggable in the future).
Configuration changes are pushed to each process when new skynet services are started. This means that starting a new service automatically advertises that service's availability to the rest of the members of the skynet cluster.
Processes are monitored, and restarted when they die, and are removed from the cluster configuration management system so that clients do not create new connections. Currently connected clients will notice these removals and adjust their internal pool of connections as services are added/removed/die.
Skynet makes heavy usage of Doozer. You'll need at least 1 Doozer instance to run Skynet, but we recommend a cluster of multiple Doozer nodes to ensure high availability. With only 1 instance you leave yourself with a single point of failure.
##Services Services are the heart of your Skynet clusters, they will accept requests via bson rpc requests, although this is abstracted away, you won't have to deal with the protocol, you will just pass objects. Keep in mind that a Service may also be a client. In the case of a Composite style application, a request could be made to one service that makes requests either synchronously or asynchronously to additional Skynet services.
#####Sweet! How do I create a service? Check out the service documentation page on the wiki: https://github.com/bketelsen/skynet/wiki/Services
Examples can be found in the examples/ directory.
##Clients Clients are responsible for sending requests to Skynet services, and processing their requests.
Clients contain a pool of connections to a given service, up to a specified size to load balance requests across. Instances are removed from Skynet when they crash, the pools are smart enough to remove any connections to any instances that are no longer available and replace them with connections to valid instances to maintain the pool.
To use the Go client in your own program to call Skynet services, see Creating a simple client The Go client is part of this project. Clients in other languages are also available:
To build a Client in your favorite language see the Skynet Protocol Guide
####Sky The "sky" command is a management gateway into the Skynet cluster. It will allow you to probe the network and look for services/versions, hosts, regions etc in your cluster, as well as run administration commands to operate on instances that match the criteria. You can register/unregister/stop/restart services as well as deploy new services to hosts matching your filters.
####Interactive Shell Another option is to use the interactive shell "sky cli". Which will open a shell you can interact with. Setting filters will allow any future commands to only apply to resources that meet those conditions. It supports history, and tab completion of commands, as well as services, hosts, regions, versions Skynet is already aware of.
####Dashboard The dashboard is a live updating web ui. Where you can see the current topology of your network, what regions/hosts/instances are up, average response times, last request, number of connections, if they are registered or not.
In the future you will be able to live search your logs, as well as see graph data surrounding the health of your cluster.
##Internals #####Query The sky command and the client connectivity logic is all backed by Query. A struct that can be used to search the cluster for instances of services, regions, hosts, service names, service versions that Skynet is currently aware of. It's exposed for any custom need you may have for searching the cluster.
#####Instance Listener You can create an instance listener by passing it a Query object, and be notified anytime an instance matching your Query is added/removed/changed.
The wiki has tons of documentation and tutorials on how to get started.
The examples/ directory has example services & clients
Also in the examples/ directory is a Vagrant setup with chef recipes to deploy a mock cluster using virtual machines so that you can see it in action. The wiki has a nice walkthrough on setting up and running a simulated cluster with Vagrant: https://github.com/bketelsen/skynet/wiki/Vagrant-Example
Work In Progress
Entire node failure / netsplit
Although a lot of work has gone into keeping instances up, and restarting, and the configuration management system to stay cleaned up. We still have a feature out standing to better handle an entire node crashing, or not being able to be communicated with.
#####Monitor CPU/Memory/Load Skynet will be aware of system utilization and number of requests going to specific instances of a service, and will be able to have a configurable threshold for it to restart or remove itself from the pool of instances for it's particular Service/Version, and return itself to the queue when the system has leveled out, or restart has completed
#####Time Series Data / Metrics We all love metrics and graphs, skynet will make sure you get your daily fix. More than likely we will utilize something like graphite to log time series data regarding number of requests, which calls are being made, response times, cpu/memory/load so that you can determine the state of your skynet cluster quickly with a dashboard of metrics.
After this functionality has been added we'd like to create a nice web interface to be hit and see live statistics going on across the system at that moment and refreshed live.
#####Test Suite / Benchmarks / Refactoring / Docs Skynet has evolved quite a bit from the original idea/implementation, much experimentation and R&D has been done to come up with the best approach, now that a lot of this has been finalized a full test suite will be coming, as well as some cleanup in areas of the codebase that were just quick prototypes to prove theories and need to be clean interfaces.
Also the addition of godocs, and other wiki pages to help better describe internals, and tips/tricks.
#####Skylib for other languages Skylib is the core of skynet's internals and is how services/clients find each other, by implementing skylib in a variety of languages we will allow services and clients of many different languages to become a part of the skynet cluster.
- Group name: Skynet-dev
- Group home page: http://groups.google.com/group/skynet-dev
- Group email address firstname.lastname@example.org
- IRC: #skynet-dev on freenode
##Issues: Github Issues now the canonical source of issues for Skynet.
##Open Source - MIT Software License Copyright (c) 2012 Brian Ketelsen
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