-- A SimGrid Lua implementation of the Chord DHT
+-- Copyright (c) 2011-2012, 2014. The SimGrid Team.
+-- All rights reserved.
+
+-- This program is free software; you can redistribute it and/or modify it
+-- under the terms of the license (GNU LGPL) which comes with this package.
+
require("simgrid")
-nb_bits = 24
-nb_keys = 2^nb_bits
-comp_size = 0
-comm_size = 10
-timeout = 50
-max_simulation_time = 1000
-stabilize_delay = 20
-fix_fingers_delay = 120
+nb_bits = 24
+nb_keys = 2^nb_bits
+comp_size = 0
+comm_size = 10
+timeout = 50
+max_simulation_time = 1000
+stabilize_delay = 20
+fix_fingers_delay = 120
check_predecessor_delay = 120
-lookup_delay = 10
+lookup_delay = 10
--- current node (don't worry, globals are duplicated in each process)
+-- current node (don't worry, globals are duplicated in each simulated process)
my_node = {
id = my_id,
next_finger_to_fix = 1,
fingers = {},
- predecessor = nil
+ predecessor = nil,
comm_recv = nil
}
-- Arguments:
-- - my id
-- - the id of a guy I know in the system (except for the first node)
-function node(my_id, known_id)
+function node(...)
+
+ -- TODO simplify the deployment file
+ local known_id
+ local args = {...}
+ my_node.id = tonumber(args[1])
+ if #args == 4 then
+ known_id = tonumber(args[2])
+ end
- simgrid.info("Hello, I'm a node")
+ -- initialize the node
+ for i = 1, nb_bits do
+ my_node.fingers[i] = my_node.id
+ end
+ my_node.comm_recv = simgrid.task.irecv(my_node.id)
-- join the ring
- local success = false
+ local join_success = false
if known_id == nil then
-- first node
create()
- success = true
+ join_success = true
else
- success = join(known_id)
+ join_success = join(known_id)
end
-- main loop
local next_check_predecessor_date = now + check_predecessor_delay
local next_lookup_date = now + lookup_delay
- local task
- my_node.comm_recv = simgrid.task.irecv(my_node.id)
+ local task, err
while now < max_simulation_time do
- task = simgrid.comm.test(node.comm_recv)
+ task, err = my_node.comm_recv:test()
if task then
-- I received a task: answer it
my_node.comm_recv = simgrid.task.irecv(my_node.id)
handle_task(task)
+ elseif err then
+ -- the communication has failed: nevermind
+ my_node.comm_recv = simgrid.task.irecv(my_node.id)
else
-- no task was received: do periodic calls
if now >= next_stabilize_date then
elseif now >= next_check_predecessor_date then
check_predecessor()
next_check_predecessor_date = simgrid.get_clock() + check_predecessor_delay
+
elseif now >= next_lookup_date then
random_lookup()
next_lookup_date = simgrid.get_clock() + lookup_delay
end
end
+-- Makes the current node leave the ring
+function leave()
+
+ simgrid.info("Leaving the ring")
+ -- TODO: notify others
+end
+
-- This function is called when the current node receives a task.
-- - task: the task received
function handle_task(task)
- local type = task[type]
+ local type = task.type
if type == "find successor" then
+ simgrid.info("Received a 'find successor' request from " .. task.answer_to ..
+ " for id " .. task.request_id)
+
-- is my successor the successor?
- if is_in_interval(task[request_id], my_node.id + 1, my_node.fingers[1]) then
- task[type] = "find successor answer"
- task[answer] = my_node.fingers[1]
- task:dsend(task[answer_to])
+ if is_in_interval(task.request_id, my_node.id + 1, my_node.fingers[1]) then
+
+ simgrid.info("Sending back a 'find successor answer' to " ..
+ task.answer_to .. ": the successor of " .. task.request_id ..
+ " is " .. my_node.fingers[1])
+
+ task.type = "find successor answer"
+ task.answer = my_node.fingers[1]
+ task:dsend(task.answer_to)
else
-- forward the request to the closest preceding finger in my table
- task:dsend(closest_preceding_node(task[request_id]))
+
+ simgrid.info("Forwarding the 'find successor' request to my closest preceding finger")
+ task:dsend(closest_preceding_node(task.request_id))
end
elseif type == "get predecessor" then
- task[answer] = my_node.predecessor
- task:dsend(task[answer_to])
+ task.type = "get predecessor answer"
+ task.answer = my_node.predecessor
+ task:dsend(task.answer_to)
elseif type == "notify" then
-- someone is telling me that he may be my new predecessor
- notify(task[request_id])
+ notify(task.request_id)
elseif type == "predecessor leaving" then
-- TODO
-- ignoring
else
- error("Unknown type of task received: " .. task[type])
+ error("Unknown type of task received: " .. task.type)
end
end
return id <= b
end
+-- Returns whether the current node is in the ring.
+function has_joined()
+
+ return my_node.fingers[1] ~= nil
+end
+
+-- Creates a new Chord ring.
+function create()
+ my_node.predecessor = nil
+ my_node.fingers[1] = my_node.id
+end
+
+-- Attemps to join the Chord ring.
+-- - known_id: id of a node already in the ring
+-- - return value: true if the join was successful
+function join(known_id)
+
+ simgrid.info("Joining the ring with id " .. my_node.id .. ", knowing node " .. known_id)
+
+ local successor = remote_find_successor(known_id, my_node.id)
+ if successor == nil then
+ simgrid.info("Cannot join the ring.")
+ return false
+ end
+
+ my_node.predecessor = nil
+ my_node.fingers[1] = successor
+ return true
+end
+
-- Returns the closest preceding finger of an id with respect to the finger
-- table of the current node.
-- - id: the id to find
function closest_preceding_node(id)
for i = nb_bits, 1, -1 do
- if is_in_interval(my_node.fingers[i].id, my_node.id + 1, id - 1) then
+ if is_in_interval(my_node.fingers[i], my_node.id + 1, id - 1) then
-- finger i is the first one before id
- return my_node.fingers[i].id
+ return my_node.fingers[i]
end
end
end
-- Finds the successor of an id
-- id: the id to find
--- return value: the id of the successor, or -1 if the request failed
+-- return value: the id of the successor, or nil if the request failed
function find_successor(id)
if is_in_interval(id, my_node.id + 1, my_node.fingers[1]) then
-- return value: the id of the successor, or nil if the request failed
function remote_find_successor(ask_to, id)
- local task = simgrid.task.new(comp_size, comm_size)
- task[type] = "find successor"
- task[request_id] = id
- task[answer_to] = my_node.id
+ local task = simgrid.task.new("", comp_size, comm_size)
+ task.type = "find successor"
+ task.request_id = id
+ task.answer_to = my_node.id
+ simgrid.info("Sending a 'find successor' request to " .. ask_to .. " for id " .. id)
if task:send(ask_to, timeout) then
-- request successfully sent: wait for an answer
+
+ simgrid.info("Sent the 'find successor' request to " .. ask_to ..
+ " for id " .. id .. ", waiting for the answer")
+
while true do
- task = simgrid.comm.wait(my_node.comm_recv, timeout)
+ task = my_node.comm_recv:wait(timeout)
my_node.comm_recv = simgrid.task.irecv(my_node.id)
if not task then
-- failed to receive the answer
+ simgrid.info("Failed to receive the answer to my 'find successor' request")
return nil
else
-- a task was received: is it the expected answer?
- if task[type] ~= "find successor answer" or task[request_id] ~= id then
+ if task.type ~= "find successor answer" or task.request_id ~= id then
-- this is not our answer
+ simgrid.info("Received another request of type " .. task.type)
handle_task(task)
else
-- this is our answer
- return task[answer]
+ simgrid.info("Received the answer to my 'find successor' request for id " ..
+ id .. ": the successor is " .. task.answer)
+ return task.answer
end
end
end
+ else
+ simgrid.info("Failed to send the 'find successor' request to " .. ask_to ..
+ " for id " .. id)
end
return successor
-- return value: the id of its predecessor, or nil if the request failed
function remote_get_predecessor(ask_to)
- local task = simgrid.task.new(comp_size, comm_size)
- task[type] = "get predecessor"
- task[answer_to] = my_node.id
+ local task = simgrid.task.new("", comp_size, comm_size)
+ task.type = "get predecessor"
+ task.answer_to = my_node.id
if task:send(ask_to, timeout) then
-- request successfully sent: wait for an answer
while true do
- task = simgrid.comm.wait(my_node.comm_recv, timeout)
+ task = my_node.comm_recv:wait(timeout)
my_node.comm_recv = simgrid.task.irecv(my_node.id)
if not task then
return nil
else
-- a task was received: is it the expected answer?
- if task[type] ~= "get predecessor answer" then
+ if task.type ~= "get predecessor answer" then
-- this is not our answer
handle_task(task)
else
-- this is our answer
-- FIXME make sure the message answers to this particular request
- return task[answer]
+ return task.answer
end
end
end
end
-- this node is a candidate to become my new successor
- if candidate ~= nil and is_in_interval(candidate, my_node.id + 1, successor -1) then
+ if candidate ~= nil and is_in_interval(candidate, my_node.id + 1, successor - 1) then
my_node.fingers[1] = candidate
end
-- - candidate the possible new predecessor
function remote_notify(notify_to, candidate_predecessor)
- local task = simgrid.task.new(comp_size, comm_size)
- task[type] = "notify"
- task[request_id] = candidate_predecessor
+ local task = simgrid.task.new("", comp_size, comm_size)
+ task.type = "notify"
+ task.request_id = candidate_predecessor
task:dsend(notify_to)
end
local id = find_successor(my_node.id + 2^i)
if id ~= nil then
if id ~= my_node.fingers[i] then
- fingers[i] = id
+ my_node.fingers[i] = id
end
my_node.next_finger_to_fix = (i % nb_bits) + 1
end
