Distributed-Blackboard/DistBlackboardCentComm.repy at master · GcherkosH/Distributed-Blackboard · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
#This program implements a LEADER ELECTION algorithm for a simple distributed blackboard using Repy and
#uses the Seattle framework to run it in distributed vessels
#========================================================================================================

#mycontext implementation of global variables
mycontext['text_area_comment']=""
mycontext['leader_ip']=""
mycontext['lead_rand_number']=""
mycontext['my_ip']=getmyip()
mycontext['my_randomnumber']=int(randomfloat()*100)
mycontext['vessels']=['129.97.74.12','192.1.249.137','200.19.159.34','140.247.60.126','108.58.13.205','211.68.70.40','128.208.4.199','193.63.75.20','194.29.178.5','193.191.148.227']
mycontext['accesslock'] = getlock()

#====================================================================================
#This function creates the leader message and sends it to sendToNeighbour() function
def propagateLeader():
  mycontext['my_ip']=getmyip()
  mycontext['accesslock'].acquire() # acquire the lock
  message='LEADER:'+mycontext['leader_ip']+':'+mycontext['lead_rand_number']
  mycontext['accesslock'].release() # release the lock
  sendToNeighbour(message)
#==================================================================================
#This function determines the neigbor and sends a mesg to the neighbor
def sendToNeighbour(message):
    ip_index=mycontext['vessels'].index(mycontext['my_ip'])
    no_of_vessels=len(mycontext['vessels'])
    #if i am the last in the list, my neighbor is the first in the listmycontext['accesslock']
    if ip_index==(no_of_vessels-1):
      my_neighbor=mycontext['vessels'][0]
    else:
      my_neighbor=mycontext['vessels'][ip_index + 1]

    #create a tcp connection and send message
    mycontext['accesslock'].acquire() # acquire the lock
    try:
      socketobject = openconn(my_neighbor,mycontext['port_number'])
      socketobject.send(message)
      socketobject.close()
    except:
      print 'No connection to neigbor'
    mycontext['accesslock'].release() # release the lock
#=====================================================================================
#commencing the leader election
def leaderElection():
  mycontext['my_ip']=getmyip()
  mycontext['accesslock'].acquire() # acquire the lock
  #initially i am leder, so i create an election and pass the msg to sendToNeighbour()
  election_msg='ELECTION:'+mycontext['my_ip']+':'+mycontext['my_ip']+':'+str(mycontext['my_randomnumber'])
  mycontext['accesslock'].release() # release the lock
  sendToNeighbour(election_msg)

#=====================================================================================
#html response to be displayed on the browser
def response(sockobj,content):
  mycontext['accesslock'].acquire() # acquire the lock
  htmlresponse = """<html> <head>
    <meta content="text/html; charset=utf-8" http-equiv="content-type">
    <title>Blackboard Group 5</title> </head> <body><h2> Board Content</h2>
    <p>"""+ content+ """</p><br>
    <h3>Submit to board<h3>
    <textarea rows="4" cols="50" name="comment" form="usrform"></textarea>
    <form action="" id="usrform" method="post"> <input type="submit"> </form>
    <h5>Leader IP Address: """+str(mycontext['leader_ip'])+"""</h5>
    <h5>Maximum Random Number: """+str(mycontext['lead_rand_number'])+""" </h5> <br> </body>  </html>"""
  sockobj.send("HTTP/1.1 200 OK\r\nContent-type: text/html\r\n" "Content-length: %i\r\n\r\n%s" % (len(htmlresponse), htmlresponse))
  mycontext['accesslock'].release() # release the lock

#========================================================================================
def board(ip, port, sockobj, thiscommhandle, listencommhandle):
  try:
    msgheader = sockobj.recv(1024) # Receive message,
  except:
    print 'Board did not receive message'
  # React depending on message type: HTTP GET or POST, or some other type of communication.
  # GET type, the vessel returns html to browser
  if msgheader.startswith( 'GET' ):
    response(sockobj,str(mycontext['text_area_comment']))
    stopcomm(thiscommhandle)

  # POST type, the vessel sends the submitted message to all the vessels
  elif msgheader.startswith( 'POST' ):
    #extract the posted content from the msgheader
    posted_comment=msgheader[msgheader.find('comment')+8:]
    response(sockobj,mycontext['text_area_comment'])
    stopcomm(thiscommhandle)

    #open tcp connection to the leader and send the posted comment
    mycontext['accesslock'].acquire() # acquire the lock
    try:
      sock = openconn(mycontext['leader_ip'], mycontext['port_number'])
      sock.send(posted_comment)
      sock.close()
    except:
      print 'Failed to connect to leader'
    mycontext['accesslock'].release() # release the lock

  # Receive message from vessels's left neighbor
  elif msgheader.startswith( 'ELECTION' ):
    message=msgheader.split(":")
    stopcomm(thiscommhandle)
    initiator_ip=message[1]
    candidate_ip =message[2]
    candidate_number=message[3]
    my_ip=mycontext['my_ip']
    my_randomnumber=mycontext['my_randomnumber']

    if initiator_ip == my_ip:
      mycontext['leader_ip']=candidate_ip
      mycontext['lead_rand_number']=candidate_number
      # propagate leader's information to right neighbor
      if mycontext['leader_ip'] is not None:
        propagateLeader()

    else:
      #i am the new candidate to be a leader if my randmom number > received random number from neighbor
      if int(my_randomnumber) > int(candidate_number):
        new_elect_msg='ELECTION:'+initiator_ip+':'+my_ip+':'+str(my_randomnumber)
        sendToNeighbour(new_elect_msg)

      #else, send the original message
      else:
        sendToNeighbour(msgheader)

  elif msgheader.startswith('LEADER'):
    message=msgheader.split(":")
    stopcomm(thiscommhandle)

    leader_ip=message[1]
    lead_rand_number=message[2]
    mycontext['accesslock'].acquire() # acquire the lock
    mycontext['leader_ip']=leader_ip
    mycontext['lead_rand_number']=lead_rand_number
    mycontext['accesslock'].release() # release the lock
    myip=mycontext['my_ip']

  else:
    message=msgheader
    stopcomm(thiscommhandle)
    #if leader, send update to all other vessels
    if mycontext['my_ip'] == mycontext['leader_ip']:
      mycontext['accesslock'].acquire() # acquire the lock
      vessels=mycontext['vessels']
      # Remove leader's ip from vessels
      if mycontext['leader_ip'] in vessels:
        vessels.remove(mycontext['leader_ip'])
      mycontext['accesslock'].release() # release the lock
      # update every other vessel
      for ip in vessels:
        mycontext['accesslock'].acquire() # acquire the lock
        try:
          socketobject = openconn(ip,mycontext['port_number'])
          socketobject.send(message)
          socketobject.close()
        except:
          print 'Connection failed'
        mycontext['accesslock'].release() # release the lock

    # Add update to mycontext['text_area_comment']
    mycontext['text_area_comment'] = mycontext['text_area_comment'] +'<br>'+ message

#====================================================================================
# program execution starts here
if callfunc == 'initialize':

  if len(callargs) > 1:
    raise Exception("Too many call arguments")

  # Running remotely (assuming that we pass input argument only remotely):
  # whenever this vessel gets a connection on its IPaddress:Clearinghouseport it'll call function board
  elif len(callargs) == 1:
    mycontext['port_number'] = int(callargs[0])
    ip = getmyip()

  # Running locally:
  # whenever we get a connection on 127.0.0.1:12345 we'll call board
  else:
    mycontext['port_number'] = 12345
    ip = '127.0.0.1'

  listencommhandle = waitforconn(ip,mycontext['port_number'],board)
  sleep(5)
  leaderElection()