--
-- mdcliapi2.lua - Majordomo Protocol Client API (async version)
--
-- Author: Robert G. Jakabosky <moc.mlaerderahs|ybbob#moc.mlaerderahs|ybbob>
--
local setmetatable = setmetatable
local mdp = require"mdp"
local zmq = require"zmq"
local zpoller = require"zmq.poller"
local zmsg = require"zmsg"
require"zhelpers"
local s_version_assert = s_version_assert
local obj_mt = {}
obj_mt.__index = obj_mt
function obj_mt:set_timeout(timeout)
self.timeout = timeout
end
function obj_mt:destroy()
if self.client then self.client:close() end
self.context:term()
end
local function s_mdcli_connect_to_broker(self)
-- close old socket.
if self.client then
self.poller:remove(self.client)
self.client:close()
end
self.client = assert(self.context:socket(zmq.DEALER))
assert(self.client:setopt(zmq.LINGER, 0))
assert(self.client:connect(self.broker))
if self.verbose then
s_console("I: connecting to broker at %s…", self.broker)
end
-- add socket to poller
self.poller:add(self.client, zmq.POLLIN, function()
self.got_reply = true
end)
end
--
-- Send request to broker and get reply by hook or crook
--
function obj_mt:send(service, request)
-- Prefix request with protocol frames
-- Frame 0: empty (REQ emulation)
-- Frame 1: "MDPCxy" (six bytes, MDP/Client x.y)
-- Frame 2: Service name (printable string)
request:push(service)
request:push(mdp.MDPC_CLIENT)
request:push("")
if self.verbose then
s_console("I: send request to '%s' service:", service)
request:dump()
end
request:send(self.client)
return 0
end
-- Returns the reply message or NULL if there was no reply. Does not
-- attempt to recover from a broker failure, this is not possible
-- without storing all unanswered requests and resending them all…
function obj_mt:recv()
self.got_reply = false
local cnt = assert(self.poller:poll(self.timeout * 1000))
if cnt ~= 0 and self.got_reply then
local msg = zmsg.recv(self.client)
if self.verbose then
s_console("I: received reply:")
msg:dump()
end
assert(msg:parts() >= 3)
local empty = msg:pop()
assert(empty == "")
local header = msg:pop()
assert(header == mdp.MDPC_CLIENT)
return msg
end
if self.verbose then
s_console("W: permanent error, abandoning request")
end
return nil -- Giving up
end
module(...)
function new(broker, verbose)
s_version_assert (2, 1);
local self = setmetatable({
context = zmq.init(1),
poller = zpoller.new(1),
broker = broker,
verbose = verbose,
timeout = 2500, -- msecs
}, obj_mt)
s_mdcli_connect_to_broker(self)
return self
end
setmetatable(_M, { __call = function(self, ...) return new(...) end })