Class: Hoodoo::Services::Discovery::ByDRb::DRbServer

Inherits:
Object
  • Object
show all
Defined in:
lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb

Overview

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

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ DRbServer

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



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# File 'lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb', line 89

def initialize
  @repository = {}
end

Class Method Details

.start(port = nil) ⇒ Object

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.



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# File 'lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb', line 63

def self.start( port = nil )

  uri = self.uri( port )

  $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) ⇒ Object

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.



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# 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

Instance Method Details

#add(resource, version, uri) ⇒ Object

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.



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# File 'lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb', line 108

def add( resource, version, uri )
  @repository[ "#{ resource }/#{ version }" ] = uri
end

#find(resource, version) ⇒ Object

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



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# File 'lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb', line 118

def find( resource, version )
  @repository[ "#{ resource }/#{ version }" ]
end

#flush ⇒ Object

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



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# File 'lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb', line 125

def flush
  @repository = {}
end

#ping ⇒ Object

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



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# File 'lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb', line 95

def ping
  return true
end

#stop ⇒ Object

Shut down this DRb service.



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# File 'lib/hoodoo/services/discovery/discoverers/by_drb/drb_server.rb', line 131

def stop
  $stop_queue.push( true )
end