Introduction to Interprocess Communication. Introduction to Interprocess Communication

Transcription

1 Introduction to Interprocess Communication Saverio Giallorenzo 1

2 The rocess Text Data Heap Stack C AddNumbers: std clc pushf.top i = 3,14 e = 2,71 y = hi x = 5 SUB1 MAIN rocess Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 2

3 rocess Control Block Text Data Heap Stack C AddNumbers: std clc pushf.top i = 3,14 e = 2,71 y = hi x = 5 SUB1 MAIN rocess process state process number process counter REGISTERS memory limits pointers Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 3

4 Interprocess Communication rocess 2 sort (4,5,2,7) merge (2,4,5,7) rocess 1 sort (11,9,14) merge (9,11,14) rocess 3 Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 4

5 Interprocess Communication rocess 2 Why do processes sort (4,5,2,7) rocess 1 communicate? Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 5

6 Interprocess Communication rocess 2 sort (4,5,2,7) rocess 1 Why do processes communicate? Information sharing - e.g., concurrent access to files; Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 5

7 Interprocess Communication rocess 2 sort (4,5,2,7) rocess 1 Why do processes communicate? Information sharing - e.g., concurrent access to files; Computation speed - same aim divided in multiple tasks; Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 5

8 Interprocess Communication rocess 2 sort (4,5,2,7) rocess 1 Why do processes communicate? Information sharing - e.g., concurrent access to files; Computation speed - same aim divided in multiple tasks; Modularity - reuse processes; Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 5

9 Interprocess Communication rocess 2 sort (4,5,2,7) rocess 1 Why do processes communicate? Information sharing - e.g., concurrent access to files; Computation speed - same aim divided in multiple tasks; Modularity - reuse processes; Convenience - multitasking. Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 5

10 Interprocess Communication rocess 2 How do processes sort (4,5,2,7) rocess 1 communicate? Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 6

11 Interprocess Communication rocess 2 sort (4,5,2,7) rocess 1 How do processes communicate? Shared Memory V Message assing Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 6

12 Shared Memory v Message assing Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 7

13 Shared Memory quick (and dirty); shared segment of memory; hack-ish, processes bypass memory protections of the OS. Saverio Giallorenzo 8

14 Message assing model scales from local to remote processes; needs a communication link Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 9

15 Message assing: the communication link Two concerns of implementation: hysical Logical Saverio Giallorenzo 10

16 Message assing: the communication link Two concerns of implementation: hysical Logical Saverio Giallorenzo 10

17 Logical Implementation Direct communication send(, msg) receive(, msg) Saverio Giallorenzo 11

18 Logical Implementation Direct communication send(, msg) receive(id, msg) (asymmetric) Saverio Giallorenzo 12

19 Logical Implementation Indirect communication send(a, msg) A receive(a, msg) Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 13

20 Logical Implementation Indirect communication send(a, msg) receive(a, msg) R A receive(a, msg) send(a, msg) S Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 14

21 Logical Implementation Synchronous communication Blocking send 1 request 2 ack receive 3 Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 15

22 Logical Implementation Synchronous communication Nonblocking send 1 send 2 2 receive Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 16

23 Logical Implementation Synchronous communication Blocking receive 1 send receive 2 3 Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 17

24 Logical Implementation Synchronous communication Nonblocking receive 1 send receive 2 Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 18

25 Logical Implementation Buffering Saverio Giallorenzo 19

26 Logical Implementation Zero Capacity Buffering 0 Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 19

27 Logical Implementation Zero Capacity Buffering Blocking 0 Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 19

28 Logical Implementation Buffering Zero Capacity Bounded Capacity Blocking Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 19

29 Logical Implementation Buffering Zero Capacity Bounded Capacity Blocking Blocking Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 19

30 Logical Implementation Buffering Zero Capacity Bounded Capacity Unbounded Capacity Blocking Blocking Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 19

31 Remote Invocation Request-reply protocols send( sum,x=17,y=25 ); // wait receive( res ); Low-level e.g., sockets receive( req ); switch ( req[0, 3] ){ case sum : res = sum( req ); break; case sub : } res = sub( req ); break; send( res ); Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 20

32 Remote Invocation Sockets try { /* make connection to server socket */ Socket toserver = new Socket( , 6013 ); rintwriter pout = new rintwriter( toserver.getoutputstream(), true ); /* write the request to the server */ pout.println( sum,x=17,y=25 ); toserver.close(); /* accept response connection from server */ tome = new ServerSocket( 6012 ); tome.accept(); InputStream in = tome.getinputstream(); BufferedReader bin = new BufferedReader( new InputStreamReader( in ) ); /* read the data from the socket */ String response = bin.readline() /* close the socket connection */ tome.close(); } catch (IOException ioe) { System.err.println(ioe) }; Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 21

33 Remote Invocation Request-reply protocols low-level support for requesting the execution of a remote operation; support for RC and RMI, discussed below Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 22

34 Remote Invocation Request-reply protocols low-level support for requesting the execution of a remote operation (HTT, FT, etc. are Request-reply protocols); support for RC and RMI (next); Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 23

35 Remote Invocation Remote rocedure Calls Communication library Client Stub rocedure Server Stub rocedure res = sum@( 17, 25 ); Low-level e.g., Sockets ossibly over App. level rotocol sum( int x, int y ){ return x + y; } Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 24

36 Remote Invocation Remote rocedure Calls programming with interfaces (recall, an interface specifies the procedures and the variables available to others); Separation of concerns: interfaces remain the same but their implementation may change; High degree of heterogeneity. Saverio Giallorenzo 25

37 Remote Invocation Remote Method Invocation Communication module Remote Reference Module Remote Reference Module proxy res =.sum( 17, 25 ); sum( int x, int y ){ return x + y; } Saverio Giallorenzo sgiallor@cs.unibo.it DISI@Unibo 26

38 Remote Invocation Remote Method Invocation Full object-oriented paradigm for programming distributed systems; Strictly Java. Saverio Giallorenzo 27

39 Remote Invocation Remote rocedure Calls Remote Method Invocation Request-reply rotocols Saverio Giallorenzo 28