Second Assignment Tutorial lecture

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1 Secnd Assignment Tutrial lecture INF5040 (Open Distributed Systems) Faraz German Department f Infrmatics University f Osl Octber 17, 2016

2 Grup Cmmunicatin System Services prvided by grup cmmunicatin systems: Abstractin f a Grup Multicast f messages t a Grup Membership f a Grup Reliable messages t a Grup Ordering f messages sent t a Grup Failure detectin f members f the Grup A strng semantic mdel f hw messages are handled when changes t the Grup membership ccur 2

3 Spread An pen surce tlkit that prvides a high perfrmance messaging service that is resilient t faults acrss lcal and wide area netwrks. Des nt supprt very large grups, but reliability and rdering des prvide a strng mdel f Integrates a membership ntificatin service int the stream f messages Supprts multiple link prtcls and multiple client interfaces The client interfaces prvided with Spread include native interfaces fr Java and C. Als nn native Pearl, Pythn and Ruby interfaces

4 Spread Prvides different types f messaging services t applicatins Messages t entire grups f recipients Membership infrmatin abut wh is currently alive and reachable Prvides bth rdering and reliability guarantees

5 Level f service When an applicatin sends a Spread message, it chses a level f service fr that message. The level f service selected cntrls what kind f rdering and reliability are prvided t that message. Spread Service Type Ordering Reliability UNRELIABLE MESS Nne Unreliable RELIABLE MESS Nne Reliable FIFO MESS FIFO by Sender Reliable CASUAL MESS Casual (Lamprt) Reliable AGREED MESS Ttal Order (Cnsistent w/ Casual) Reliable SAFE MESS Ttal Order Safe

6 Ordering Nne N rdering guarantee Any ther message sent with Nne rdering can arrive befre r after this message FIFO by Sender All messages sent by this cnnectin f FIFO rdering are delivered in FIFO rder Causal (Lamprt) See TvS 6.2 All messages sent by all cnnectins are delivered in an rder cnsistent with Causal rder (Lamprt) Cnsistent with FIFO rdering Ttal Order (Cnsistent w/causal) All messages sent by all cnnectins are delivered in the exact same rder t all recipients Cnsistent with Causal rder

7 Reliability Unreliable Reliable Safe The message may be drpped r lst The message will nt be recvered by Spread The message will be reliably delivered t all recipients wh are members f the grup t which the message was sent Spread will recver message t vercme any netwrk lsses The message will nly be delivered t a recipient if the daemn that recipient is cnnected has the message The daemn shuld knws all ther Spread daemns in the netwrk If a membership change ccurs, and as a result the daemn cannt determine whether all daemns in the ld membership have the message, then the daemn will deliver the Safe message after a TRANSITIONAL_MEMBERSHIP message.

8 Dwnlad and Installatin Spread can be dwnladed frm: I recmmend yu t dwnlad bth the binaries and surce Binaries cntains the daemn distributin fr different architecture Surce cntains the Spread surce cde and example apps Example f cnfiguratin file (sample.spread.cnf) in the dcs flder. Run the Spread daemn Yu can use the Spread mnitr t check the status f yur daemn :./spread l y c spread.cnf and./spmnitr

9 Java Interface t Spread Tlkit The Spread library cnsists f a package, 10 classes. spread Eclipse: Imprt the classes int a new Java prject r use the Ant build file Main classes: SpreadCnnectin, which represents a cnnectin t a daemn, SpreadGrup, which represents a spread grup SpreadMessage, which represents a message that is either being sent r being received with spread.

10 Cnnecting/Discnnecting T establish a cnnectin t a spread daemn SpreadCnnectin cnnectin = new SpreadCnnectin(); cnnectin.cnnect(inetaddress.getbyname( "daemn.address.cm"), 1010, "privatename", false, false); Server Address Prt Unique Cnnectin name T terminate the cnnectin t the daemn, cnnectin.discnnect();

11 Jining/Leaving T jin a grup n the cnnectin SpreadGrupgrup = new grup.jin(cnnectin, SpreadGrup(); "grup"); Spread cnnectin n Which the grup is jined Name f the grup t jin T leave a grup: grup.leave();

12 Multicasting T multicast a message t ne r mre grups: SpreadMessage message = new SpreadMessage(); message.setdata(data); message.addgrup("grup"); message.setreliable(); This creates a new utging message T send the message: cnnectin.multicast(message);

13 Receiving T receive a message SpreadMessage message = cnnectin.receive(); receive() will blck until a message is available if(message.isregular()) System.ut.println("New message frm " + message.getsender()); else System.ut.println("New membership message message.getmembershipinf().getgrup()); return a MembershipInf bject, which prvides infrmatin abut the membership change

14 Message Factry A utility included with the java interface t spread An bject f the MessageFactry class is used t generate any number f utging messages based n a default message. messagefactry = new MessageFactry(message); T change the default at a later time messagefactry.setdefault(message); T get a message frm the message factry SpreadMessage message = messagefactry.createmessage();

15 Listeners An alternative way f receiving messages Interfaces: BasicMessageListener AdvancedMessageListener cnnectin.add(listener); After being added t a cnnectin, the listener will be alerted whenever a new message is received n the cnnectin. T remve a listener frm the cnnectin cnnectin.remve(listener);

16 Exceptins When an errr ccurs in a Spread methd, a SpreadExceptin is thrwn E.g. receive() is called n a SpreadCnnectin() bject befre cnnect() is called n that bject Any methd that is declared as thrwing a SpreadExceptinmust be placed within a try catch blck try{ cnnectin.multicast(message); }catch(spreadexceptin e){ e.printstacktrace (); System.exit(1); }

17 Secnd Prgramming Assignment A distributed applicatin that mdels a replicated bank accunt Implementatin Replicated state machine paradigm Grup cmmunicatin System Architecture A standard Spread server (daemn) A set f clients representing the replicas

18 Tasks Create a cnnectin t a Spread server. Initialize the balance n the accunt t 0.0. Jin a grup whse name is <accunt name>. Wait until it detects that <number f replicas> clients have jined the grup. Applicatin starts frm this pint, but shuld handle the dynamic additin f new replicas. The client shuld receive and analyze messages abut membership changes.

19 Cmmands t be accepted by the client balance Print the current balance n the accunt. depsit <amunt> Increase r decrease the balance by <amunt>. On all the replicas in the grup. addinterest <percent> Increase the balance by <percent> percent f the current value. On all the replicas in the grup. exchange <frm> <t> Change the currency f the accunt frm e.g. NOK t USD. Check currency table in assignment descriptin fr exchange rates. memberinf Prints the names f the current members f the grup. sleep <duratin> exit Let the client t d nthing fr <duratin> secnds. It is nly useful in a batch file.

20 Testing envirnment Spread is installed in all linux ifi cmputers /lcal i.e. /lcal/bin, /lcal/lib etc. Daemn cnfiguratin/addresses fr the assignment Yu can use any ifi machine t start yur wn server: spread -l y -c spread.cnf Example address: rubin.ifi.ui.n 4333 Yu can run the server and the clients in the same machine but it is a gd idea t test yur applicatin in a distributed envirnment with mre than 3 distributed clients.

21 Synpsis f running the client Fr Java java accuntreplica <server address> <accunt name> <number f replicas> [file name] Yu can als develp a graphical user interface if yu d nt want t use the cmmand line.

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