class Hoodoo::Services::Discovery::ByDRb::DRbServer

A registry of service endpoints, implenented as a DRB server class. An internal implementation detail of Hoodoo::Services::Middleware, in most respects.

Public Class Methods

new() click to toggle source

Create an instance ready for use as a DRb “front object”.

# File lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb, line 100
def initialize
  @repository = {}
end

start( port = nil ) click to toggle source

Start the DRb server. Does not return (joins the DRb thread). If the server is already running, expect an “address in use” connection exception from DRb.

port: Passed to ::uri method.

# File lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb, line 63
def self.start( port = nil )

  uri = self.uri( port )

  # $SAFE and taint tracking is being removed from ruby 2.7+
  # https://bugs.ruby-lang.org/issues/16131
  # Set to 0 to disable taint tracking in earlier versions
  $SAFE = 0

  # Have to allow a tained port string from "outside" just to be able
  # to start the service on a given port; so untaint that deliberately.
  #
  # http://ruby-doc.com/docs/ProgrammingRuby/html/taint.html

  uri.untaint()
  $stop_queue = ::Queue.new

  ::DRb.start_service( uri,
                       FRONT_OBJECT,
                       :tcp_acl => LOCAL_ACL )

  # DRB.thread.exit() does not reliably work; sometimes, it just hangs
  # up. I don't know why. On OS X and under Travis, sporadic failures
  # to return from the "stop()" method would result. Instead, we use a
  # relatively elaborate queue; sit here waiting for a message to be
  # pushed onto it, then just let this method exit naturally, ignoring
  # the value that appeared on the queue.
  #
  # The sleep makes it more reliable too, indicating some kind of nasty
  # race condition on start-vs-wait-to-shutdown.

  sleep( 1 )
  $stop_queue.pop()
end

uri( port = nil ) click to toggle source

URI for DRb server used during local machine development as a registry of service endpoints. Whichever service starts first runs the server which others connect to if subsequently started.

port: Optional integer port number for DRb service. If specified, this is used; else the HOODOO_DISCOVERY_BY_DRB_PORT_OVERRIDE environment variable is used; else a default of 8787 is chosen. Passing nil explicitly also leads to the use of the environment variable or default value.

# File lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb, line 43
def self.uri( port = nil )

  port ||= ENV[ 'HOODOO_DISCOVERY_BY_DRB_PORT_OVERRIDE' ] || 8787

  # Use IP address, rather than 'localhost' here, to ensure that "address
  # in use" errors are raised immediately if a second server startup
  # attempt is made:
  #
  #   https://bugs.ruby-lang.org/issues/3052
  #
  "druby://127.0.0.1:#{ port }"

end

Public Instance Methods

add( resource, version, uri ) click to toggle source

Add an endpoint to the list. If the endpoint was already added, it will be overwritten with the new data.

resource: Resource as a String or Symbol, e.g. “Product”
version: Endpoint’s implemented API version as an Integer, e.g. 1
uri: URI at which this service may be accessed, including the endpoint path (e.g. “localhost:3002/v1/products”), as a String.

# File lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb, line 119
def add( resource, version, uri )
  @repository[ "#{ resource }/#{ version }" ] = uri
end

find( resource, version ) click to toggle source

Find an endpoint in the list. Returns URI at which the service may be accessed as a String, or ‘nil’ if not found.

resource: Resource as a String or Symbol, e.g. “Product”
version: Endpoint’s implemented API version as an Integer, e.g. 1

# File lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb, line 129
def find( resource, version )
  @repository[ "#{ resource }/#{ version }" ]
end

flush() click to toggle source

Flush out the repository, clearing all stored service records. This is usually for test purposes only.

# File lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb, line 136
def flush
  @repository = {}
end

ping() click to toggle source

Check to see if this DRb service is awake. Returns true.

# File lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb, line 106
def ping
  return true
end

stop() click to toggle source

Shut down this DRb service.

# File lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb, line 142
def stop
  $stop_queue.push( true )
end