+++ /dev/null
--- 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
-check_predecessor_delay = 120
-lookup_delay = 10
-
--- current node (don't worry, globals are duplicated in each simulated process)
-my_node = {
- -- FIXME: my_id does not exist.
- id = my_id,
- next_finger_to_fix = 1,
- fingers = {},
- predecessor = nil,
- comm_recv = nil
-}
-
--- Main function of each Chord process
--- Arguments:
--- - my id
--- - the id of a guy I know in the system (except for the first node)
-function node(...)
-
- simgrid.debug("Hi! This is my first message; I just entered the program!")
- -- TODO simplify the deployment file
- local known_id
- local args = {...}
- my_node.id = math.tointeger(args[1])
- simgrid.debug("My id is now " .. my_node.id)
- if #args == 4 then
- known_id = math.tointeger(args[2])
- simgrid.info("Updated my known_id to " .. known_id)
- end
-
- -- initialize the node and the fingertable;
- -- at the beginning, this node only knows itself (we need to discover others)
- for i = 1, nb_bits, 1 do
- my_node.fingers[i] = my_node.id
- end
-
- -- Let's make sure we can receive messages!
- my_node.comm_recv = simgrid.task.irecv(my_node.id)
-
- -- join the ring
- local join_success = false
- --simgrid.info(known_id)
-
- if known_id == nil then
- -- only the first node ("Jacqueline") will enter here
- -- as configured in file ../../msg/chord/chord.xml
- simgrid.debug("I'm the node that is in charge. Going to create everything.")
- create()
- join_success = true
- else
- -- Communicate to the first node and join the ring
- -- This will also initialize
- -- my_node.predecessor and my_node.successor
- join_success = join(known_id)
- end
-
- -- At this point, finger[1] does not necessarily actually point
- -- to the *real* successor; it might be that the first node still
- -- didn't notify us that another node joined with
- -- an ID that satisfies my_id <= ID <= current_successorId
-
- -- TODO Remove this, but make sure my_node.predecessor is initialized somewhere
- --if my_node.id == 1 then
- --my_node.predecessor = 1
- --end
-
- -- main loop
- if join_success then
-
- local now = simgrid.get_clock()
- local next_stabilize_date = now + stabilize_delay
- local next_fix_fingers_date = now + fix_fingers_delay
- local next_check_predecessor_date = now + check_predecessor_delay
- local next_lookup_date = now + lookup_delay
-
- local task, err
-
- simgrid.debug("I'm now entering the main loop.")
-
- while now < max_simulation_time do
-
- task, err = my_node.comm_recv:test()
- simgrid.info(now .. " " .. next_stabilize_date .. " " .. now + stabilize_delay .. " " .. next_fix_fingers_date .. " " .. next_check_predecessor_date .. " " .. next_lookup_date)
-
- if task then
- -- I received a task: answer it
- simgrid.info("I received a task of type '" .. task.type .."'! My id is " .. my_node.id)
- my_node.comm_recv = simgrid.task.irecv(my_node.id)
- handle_task(task)
- elseif err then
- -- the communication has failed: nevermind, we'll try again
- simgrid.info("Error while receiving a task! My id is " .. my_node.id)
- my_node.comm_recv = simgrid.task.irecv(my_node.id)
- else
- -- no task was received: do periodic calls
-
- if now >= next_stabilize_date then
- simgrid.debug("Stabilizing...")
- stabilize()
- simgrid.debug("Finished stabilizing!")
- next_stabilize_date = simgrid.get_clock() + stabilize_delay
-
- --elseif now >= next_fix_fingers_date then
- --fix_fingers()
- --next_fix_fingers_date = simgrid.get_clock() + fix_fingers_delay
-
- --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()
- --simgrid.debug("I'm now executing a lookup, as lookup_delay makes me do this. " .. simgrid.get_clock())
- --next_lookup_date = simgrid.get_clock() + lookup_delay
-
- else
- ---- nothing to do: sleep for a while
- simgrid.debug("Didn't have to stabilize, update my fingers, check my predecessors or do a random lookup; hence, I'm starting to sleep now...")
- simgrid.process.sleep(5)
- simgrid.debug("Slept for 5s")
- end
- end
- now = simgrid.get_clock()
- end -- while
-
- -- leave the ring
- leave()
- end
-end
-
--- Makes the current node leave the ring
-function leave()
-
- simgrid.info("Leaving the ring, because max_simulation_time was reached.")
- -- TODO: notify others
-end
-
--- This function is called when the current node receives a task
--- and can not immediately deal with it; for instance, if the host
--- waits on a response for a 'find successor' query but receives a
--- 'get predecessor' message instead; we cannot just discard this
--- message so we deal with it here.
---
--- - task: the task received
-function handle_task(task)
-
- simgrid.debug("Handling task in handle_task()")
- local type = task.type
-
- if type == "find successor" then
-
- task.answer_to = math.tointeger(task.answer_to)
- task.request_id = math.tointeger(task.request_id)
-
- simgrid.info("Received a 'find successor' request from " .. string.format("%d", task.answer_to) ..
- " for id " .. string.format("%d", task.request_id))
-
- -- Is my successor have the right host? This can happen if there are holes
- -- in the ring; for instance, if my id is 13 and my successor is 17 and
- -- 14,15,16 don't exist but I'm asked for 15, then yes, 17 is the right
- -- answer to the request.
- --
- -- Test: my_node.id + 1 <= task.request_id <= my_node.fingers[1]
- -- ^^^
- -- TODO: Why the +1? We could receive this message from a host that forwarded
- -- this message (and the original sender doesn't know us),
- -- so why do we exclude ourselves?
- 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 " ..
- string.format("%d", task.answer_to) .. ": the successor of " .. string.format("%d", task.request_id) ..
- " is " .. string.format("%d", my_node.fingers[1]))
-
- task.type = "find successor answer"
- -- TODO: Can we remove the "" here?
- task.answer = math.tointeger(my_node.fingers[1])
- simgrid.info("Answer" .. task.answer)
- task:dsend(math.tointeger(task.answer_to))
- else
- -- forward the request to the closest preceding finger in my table
-
- 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
- simgrid.info("Received a 'find predecessor' request from " .. string.format("%d", task.answer_to) ..
- " for id. Sending back an answer.")
-
- task.type = "get predecessor answer"
-
- --for i,v in pairs(my_node) do
- --print(my_node.id, i, v)
- --end
- --print(my_node.predecessor)
- if my_node.predecessor ~= nil then
- task.answer = math.tointeger(my_node.predecessor)
- --print(my_node.predecessor)
- else
- -- FIXME: This is completely wrong here. Fix this;
- -- we need to figure out what to send if we don't know our
- -- predecessor yet (this DOES happen and this means that task.answer
- -- is initialised with nil and when task.answer is accessed (not here), it will
- -- break in Lua 5.3 (because it is nil).
- simgrid.critical("Don't know my predecessor yet!")
- my_node.predecessor = remote_get_predecessor(my_node.fingers[1])
- task.answer = my_node.predecessor
- end
-
- --print("It will break now, since task.answer is nil here.")
- --task.answer = my_node.predecessor
- --print(task.answer)
- --print("Before")
- task:dsend(math.tointeger(task.answer_to))
- --print("After dsend returned")
-
- elseif type == "notify" then
- -- someone is telling me that he may be my new predecessor
- simgrid.info("Host id " .. task.request_id .. " wants to be my predecessor")
- notify(math.tointeger(task.request_id))
-
- elseif type == "predecessor leaving" then
- -- TODO
- simgrid.debug("predecessor leaving")
-
- elseif type == "successor_leaving" then
- -- TODO: We could / should use something like table.remove(my_node.fingers, 1) here
- simgrid.debug(type)
-
- elseif type == "find successor answer" then
- -- ignoring, this is handled in remote_find_successor
- simgrid.debug(type)
-
- elseif type == "get predecessor answer" then
- -- ignoring, this is already handled in
-
- else
- error("Unknown type of task received: " .. task.type)
- end
-
- simgrid.info("I'm leaving handle_task() now.")
-end
-
--- Returns whether an id belongs to the interval [a, b[.
--- The parameters are normalized to make sure they are between 0 and nb_keys - 1.
--- 1 belongs to [62, 3].
--- 1 does not belong to [3, 62].
--- 63 belongs to [62, 3].
--- 63 does not belong to [3, 62].
--- 24 belongs to [21, 29].
--- 24 does not belong to [29, 21].
-function is_in_interval(id, a, b)
- -- normalize the parameters
- -- TODO: Currently, nb_bits = 24; so a,b,id < 24! Really?
- id = id % nb_bits
- a = a % nb_bits
- b = b % nb_bits
-
- -- make sure a <= b and a <= id
- if b < a then
- b = b + nb_keys
- end
-
- if id < a then
- id = id + nb_keys
- end
-
- return id <= b
-end
-
--- Returns whether the current node is in the ring.
-function has_joined()
-
- return my_node.fingers[my_node.id] ~= nil
-end
-
--- Creates a new Chord ring.
-function create()
- simgrid.debug("I've now initialized my predecessor and fingertable.")
- --my_node.predecessor = my_node.id
- 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)
- simgrid.info("Returned from remote_find_successor; my successor is " .. successor)
- if successor == nil then
- simgrid.critical("Cannot join the ring.")
- return false
- end
-
- -- We don't know the predecessor yet, so we initialize it with NULL
- my_node.predecessor = nil
- my_node.fingers[1] = successor
-
- -- Everything was successfull!
- 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
--- - return value: the closest preceding finger of that id
-function closest_preceding_node(id)
-
- for i = nb_bits, 1, -1 do
- if is_in_interval(my_node.fingers[i], my_node.id + 1, id - 1) then
- -- finger i is the first one before id
- simgrid.info("fix_fingers: The closest preceding node for " .. id .. " is finger " .. i .. " (node " .. my_node.fingers[i] .. ")")
- 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 nil if the request failed
-function find_successor(id)
-
- if is_in_interval(id, my_node.id + 1, my_node.fingers[1]) then
- -- my successor is the successor
- simgrid.info("Looking for successor of " .. id .. ", but I determined it's my own successor: " .. my_node.fingers[1])
- return my_node.fingers[1]
- else
- -- ask to the closest preceding finger in my table
- simgrid.info("fix_fingers: Looking for successor of " .. id .. ", checking closest preceding node")
- local ask_to = closest_preceding_node(id)
- simgrid.info("fix_fingers: Looking for successor of " .. id .. ", checking closest preceding node")
- return remote_find_successor(ask_to, id)
- end
-
-end
-
--- Asks a remote node the successor of an id.
--- ask_to: id of a remote node to ask to
--- id: the id to find
--- 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 -- This is the id we want to find
- task.answer_to = my_node.id -- This is where the answer needs to go
- -- (back to us)
-
- simgrid.info("Sending a 'find successor' request to " .. ask_to .. " for id " .. id .. " (timeout=".. timeout .. ")")
- if task:send(ask_to, timeout) then
- -- request successfully sent: wait for an answer
-
- while true do
- simgrid.info("New iteration in while loop of remote_find_successor(); I'm still waiting for a response!")
- --print(task.request_id)
- simgrid.info("Starting to wait for a message; timeout=" .. timeout)
- task = my_node.comm_recv:wait(timeout)
- simgrid.info("Finished to wait")
- -- TODO Do we need this?
- --for i,v in pairs(task) do
- --print(i, v)
- --end
- --simgrid.info("I will crash!")
- --task.answer = math.tointeger(task.answer)
- --simgrid.info("Ich denke task.type ist leer")
- --simgrid.info("Before irecv: " .. my_node.id)
-
- -- Even if the recv above failed (timeout occurred) -- we want to be
- -- able to receive a message if it comes in, even without us explicitly
- -- calling the recv() method.
- my_node.comm_recv = simgrid.task.irecv(my_node.id)
-
- if not task then
- -- failed to receive the answer
- return nil
- else
- -- a task was received: is it the expected answer (i.e., the response to
- -- our query and for the id we're interested in)
- if task.type ~= "find successor answer" or task.request_id ~= id then
- -- this is not our answer, but we still need to handle it.
- simgrid.info("Wrong request of type " .. task.type .. " received, expected 'find successor answer'")
- handle_task(task)
-
- else
- -- this is our answer
- simgrid.info("Received the answer to my 'find successor' request for id " ..
- id .. ": the successor is " .. task.answer)
-
- -- TODO: Do we need math.tointeger here?
- return math.tointeger(task.answer)
- end
- end
- end
- else
- simgrid.info("Failed to send the 'find successor' request to " .. ask_to ..
- " for id " .. id)
- end
-
- -- This can never be reached, because if this host finds the successor, it
- -- will return it right away!
- simgrid.info("Whooops! I should never reach this statement, because I didn't find a successor!")
-
- -- We need to return the successor here
-end
-
--- Asks a remote node its predecessor.
--- ask_to: id of a remote node to ask to
--- 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 = math.tointeger(my_node.id)
- -- TODO c.heinrich: Remove this
- --task.note = "Bla " .. ask_to .. " at time " .. simgrid.get_clock()
-
- simgrid.info("Sending request for '" .. task.type .."' to id '" .. ask_to .. "'")
- if task:send(ask_to, timeout) then
- simgrid.info("Done sending the request to " .. ask_to)
- -- request successfully sent: wait for an answer
- -- We need to iterate here because we might receive other
- -- messages too (but not the answer to the request we just sent);
- -- hence, we loop here.
- while true do
- simgrid.info("Starting to wait. My id: " .. my_node.id)
- task = my_node.comm_recv:wait(timeout)
- simgrid.info("Finished to wait. My id: " .. my_node.id .. " ask_to is " .. ask_to)
- my_node.comm_recv = simgrid.task.irecv(my_node.id)
-
- if not task then
- -- failed to receive the answer
- simgrid.info("Task not received - is null?")
- return nil
- else
- -- a task was received: is it the expected answer?
- if task.type ~= "get predecessor answer" then
- -- this is not our answer
- simgrid.info("Task is NOT 'get predecessor answer'")
- handle_task(task)
- else
- -- this is our answer
- -- FIXME make sure the message answers to this particular request
- --simgrid.info(task.answer)
- for i,v in pairs(task) do
- print(my_node.id, i, v)
- end
- simgrid.info("Task is answer for predecessor! The answer is: ")
- if (task.answer) then print("NIL!\n") else print("Not NIL\n") end
- return task.answer
- end
- end
- end
- end
-
- return successor
-end
-
--- Checks the immediate successor of the current node.
-function stabilize()
- local candidate
- local successor = my_node.fingers[1]
- if successor ~= my_node.id then
- simgrid.info("Getting remote predecessor from ".. successor)
- candidate = remote_get_predecessor(successor)
- simgrid.info("Received ".. candidate .. " as candidate")
- else
- candidate = my_node.predecessor
- end
-
- simgrid.info("Still stabilizing")
- -- candidate might become my new successor
- if candidate ~= nil and is_in_interval(candidate, my_node.id + 1, successor - 1) then
- simgrid.info("I'm updating my successor to " .. math.tointeger(candidate))
- my_node.fingers[1] = math.tointeger(candidate)
-
- -- If candidate is not my_node.id, then I should notify candidate that I'm here.
- -- (So this node updates it's predecessor to me)
- --remote_notify(candidate, my_node.id)
- end
-
- simgrid.info("Successor: " .. successor .. " and my id: " .. my_node.id)
- -- If candidate is nil, this means that our successor has no predecessor.
- -- So we should tell him about us...
- -- TODO: I think a host that receives a message could automatically add
- -- this other node as a predecessor if it doesn't have any... needs to
- -- be implemented somewhere else, not here.
- if candidate == nil and successor ~= my_node.id then
- remote_notify(successor, my_node.id)
- end
-end
-
--- Notifies the current node that its predecessor may have changed
--- - candidate_predecessor: the possible new predecessor
-function notify(candidate_predecessor)
- if my_node.predecessor == nil or is_in_interval(candidate_predecessor,
- my_node.predecessor + 1, my_node.id - 1) then
- simgrid.info("Updated my predecessor to " .. candidate_predecessor)
- my_node.predecessor = math.tointeger(candidate_predecessor)
- end
-end
-
--- Notifies a remote node that its predecessor my have changed.
--- - notify_to
--- - candidate the possible new predecessor
-function remote_notify(notify_to, candidate_predecessor)
-
- simgrid.info("Updating someone else's predecessor (id: " .. notify_to .. " predecessor to ".. candidate_predecessor .. ")")
- local task = simgrid.task.new("", comp_size, comm_size)
- task.type = "notify"
- task.request_id = candidate_predecessor
- task:dsend(notify_to)
-end
-
--- Refreshes the finger table of the current node,
--- one finger per call.
-function fix_fingers()
-
- local i = math.tointeger(my_node.next_finger_to_fix)
- local id = find_successor(math.tointeger(my_node.id + 2^i))
- simgrid.info("Called fix_fingers(). Next finger to fix: " .. i .. " and I will check " .. my_node.id + 2^i .. ". Request returned " .. id)
-
- if id ~= nil then
- if id ~= my_node.fingers[i] then
- my_node.fingers[i] = id
- simgrid.info("fix_fingers: Updated finger " .. i .. " to " .. id)
- else
- simgrid.info("fix_fingers: id is " .. id)
- end
- my_node.next_finger_to_fix = (i % nb_bits) + 1
- end
-end
-
--- Checks whether the predecessor of the current node has failed.
-function check_predecessor()
- -- TODO
-end
-
--- Performs a find successor request to an arbitrary id.
-function random_lookup()
-
- find_successor(1337)
-end
-
-simgrid.platform(arg[1] or "../../msg/msg_platform.xml")
-simgrid.application(arg[2] or "../../msg/chord/chord90.xml")
-simgrid.run()
