uScale Loadbalancer

                           __
    __  ________________ _/ /__ 
   / / / / ___/ ___/ __ `/ / _ \
  / /_/ (__  ) /__/ /_/ / /  __/
  \__,_/____/\___/\__,_/_/\___/ 

The uScale loadbalancer is a simple high-availability loadbalancer written in C# using Watson and can be used with any HTTP/HTTPS application.

Setup

Run the app with setup in the command line arguments to run the setup script and create a system.json file.

Definitions

• A 'Host' is defined as a virtual resource accessible by hostname as found in the HTTP request's Host header. Hosts is an array, so you can have multiple managed virtual resources

• A 'Node' is a physical resource mapped to a host by its hostname and port. Nodes is an array, so you can have multiple nodes mapping to a host

• Nodes are polled at an interval according to their configuration, and removed from rotation when the maximum number of failures are reached

• Node polling continues while a node is failed to detect return-to-service conditions

• The HeartbeatUrl for a Node must be a full URL including the protocol, i.e. http://10.1.1.1:80/loopback. This URL must always return a 200 to indicate that the Node is online and available

• The HandlingMode should either be Proxy or Redirect:

  • Proxy: uscale will submit a request on behalf of the requestor and marshal the response back to the requestor.
  • Redirect: uscale will send an HTTP redirect according to the configuration

• The BalancingScheme should always be set to RoundRobin (for now)

Performance and Scale

It is recommended that you use Redirect for HandlingMode as this will unburden uscale from having to proxy each connection.

Sample Configuration

{
  "EnableConsole": true,
  "RedirectStatusCode": 302,
  "RedirectStatusString": "Moved Temporarily",
  "Hosts": [
    {
      "Name": "MyApp",
      "HttpHostNames": [
        "www.myapp.com",
        "myapp.com"
      ],
      "Nodes": [
        {
          "Hostname": "10.1.1.1",
          "Port": 80,
          "Ssl": false,
          "HeartbeatUrl": "http://10.1.1.1:80/loopback",
          "PollingIntervalMsec": 2500,
          "MaxFailures": 4,
          "Failed": false
        },
        {
          "Hostname": "10.1.1.2",
          "Port": 80,
          "Ssl": false,
          "HeartbeatUrl": "http://10.1.1.2:80/loopback",
          "PollingIntervalMsec": 2500,
          "MaxFailures": 4,
          "Failed": false
        }
      ],
      "LastIndex": 0,
      "BalancingScheme": "RoundRobin",
      "HandlingMode": "Redirect",
      "AcceptInvalidCerts": true
    }
  ],
  "Server": {
    "DnsHostname": "+",
    "Port": 9000,
    "Ssl": false
  },
  "Auth": {
    "AdminApiKeyHeader": "x-api-key",
    "AdminApiKey": "admin"
  },
  "Logging": {
    "SyslogServerIp": "127.0.0.1",
    "SyslogServerPort": 514,
    "MinimumSeverityLevel": 1,
    "LogRequests": false,
    "LogResponses": false,
    "ConsoleLogging": true
  },
  "Rest": {
    "UseWebProxy": false,
    "WebProxyUrl": "",
    "AcceptInvalidCerts": true
  }
}

Admin APIs

Using the admin API key, a set of RESTful APIs can be used to gather visibility into the loadbalancer during runtime. The admin API key header defined in the Auth section of the config can be included as a header or as a querystring key-value pair.

GET /_loadbalancer/config?x-api-key=admin
GET /_loadbalancer/connections?x-api-key=admin
GET /_loadbalancer/hosts?x-api-key=admin