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Discovery application

Goal

Wanna scale some apps ? Want to automatically reconfigure loadbalancers ? Clusters ? :o

Give this app some arguments and it'll do the work :

  • subnet (CIDR formatted)
  • a check to issue on all hosts of specified subnet (see Checks)
  • action to do if a host is found (see Actions)
  • action to do if a host disappeared (see Actions)

I'll need a Redis endpoint to work !

Checks

  • Supported:
    • TCP connection
  • Planned:
    • HTTP request

Actions

  • Supported:
    • Remote shell exec via SSH
  • Planned:
    • HTTP request

Actions support substituing :

  • <HOST> is a specific host targeted by a check
  • <TIME> will be the time when the action was triggered

Basic usage

// Subnet on which do the tests : <SUBNET_ADDRESS> CIDR-formatted like "192.168.1.0/24"
Subnet yourNetwork = new Subnet(<SUBNET_ADDRESS>);

// Redis connection to use
Stocker redis = new Stocker(<REDIS_IP_ADDRESS>, <REDIS_PORT>);

// Action to do if a host is up
HostAction actionIfUp = new HostAction(HostAction.ActionType.SSHExec,
     <SSH_HOST>, <SSH_PORT>, <SSH_USER>, <SSH_PASS>,
     "echo \"<HOST> became UP at <TIME>\"  >> /log/file");

// Action to do if a host is down
HostAction actionIfDown = new HostAction(HostAction.ActionType.SSHExec,
     <SSH_HOST>, <SSH_PORT>, <SSH_USER>, <SSH_PASS>, 
     "echo \"<HOST> became DOWN at <TIME>\"  >> /log/file");

// Issue discovery
Discover disco = new Discover(Discover.CheckType.tcp, yourNetwork, 6379, actionIfUp, actionIfDown, redis, "SuperNetworkName");
disco.startDiscovery();

Docker environment

Intended for test purposes only

Use the docker-compose.yml file to spin up three containers and a dedicated network

  • a Redis host
  • an alpine-based SSH server to receive actions
    • the Discovery service will write in the homedir of a user called John (/home/John) when a up is up or down
  • a dotnet container with application mounted in /app
$ cd Discovery
// Switch on docker_tests branch
$ git checkout docker_tests

$ docker-compose up -d

// This is manually done. Intended for test purposes. 
$ docker exec -it discovery_disco_1 bash
// Cd in application directory
root@disco:/# cd /app
// Get the libs
root@disco:/app# dotnet restore
// Run the app. The subnet will be scanned onlyn once for test purposes.
root@disco:/app# dotnet run

// You can spin up additional containers to scan with the following command (or another service who is listening on port TCP 6379 (see Program.cs))
$ docker run -d -p 6379:6379 --network discovery_disco_net redis

// You can SSH with John's account on SSH server to see the logfile :
$ ssh john@localhost -p 4444
sshserver:~$ ls

TODO

See Projects.