1. A Brief Intro to the RPC Project Framework
COMP 117: Internet Scale Distributed Systems (Spring 2017)
A Brief Intro to the RPC Project Framework
Noah Mendelsohn
Tufts University
Web:

2. Getting the sample code
git clone /comp/117/files/RPC.samples
Instructions and details in RPC assignment handout

3. TCP vs. UDP

4. Streams not messages UDP messages TCP streams COMP 117 support
Limited size
Best-effort delivery
If they arrive, you get the whole message at once
TCP streams
Reliable delivery unless connection breaks
Byte streams: “unlimited” length, no message boundaries
You can write 50 bytes then 30 bytes; reader can read 35 bytes then 45
You might do a 10000byte write, but reader may see only a few on first read
COMP 117 support
Framework: c150streamsocket.h
Demo code: pingstreamclient.cpp, pingstreamserver.cpp (in RPC.samples)
You do not have to submit modified versions of these

5. Review From the Earlier Lecture On Remote Procedure Call

6. RPC: Call remote functions automatically
float sqrt(float n) { …compute sqrt…
return result; }
x = sqrt(4)
CPU
Memory
Storage
CPU
Memory
Storage
float sqrt(float n) { send n;
read s;
return s; }
proxy
Request
invoke sqrt(4)
void doMsg(Msg m) { s = sqrt(m.s);
send s; }
stub
Response
result=2 (no exception thrown)
Interface definition: float sqrt(float n);
Proxies and stubs generated automatically
RPC provides transparent remote invocation

7. How the Demo Programs Work

8. Demo program uses function w/no arguments
This client
int main() {
func1() }
simplefunctionclient.cpp
CPU
Memory
Storage
CPU
Memory
Storage

9. Demo program uses function w/no arguments
…is calling this function
int main() {
func1() }
void func1() { return; }
simplefunctionclient.cpp
CPU
Memory
Storage
CPU
Memory
Storage
Interface definition file: simplefunction.idl
void func1();

10. Demo program uses function w/no arguments
Sample proxy
int main() {
func1() }
void func1() { return; }
simplefunctionclient.cpp
CPU
Memory
Storage
CPU
Memory
Storage
simplefunction.cpp
void void() { send func1;
read DONE; }
simplefunction.proxy.cpp

11. Demo program uses function w/no arguments
int main() {
func1() }
void func1() { return; }
simplefunctionclient.cpp
CPU
Memory
Storage
CPU
Memory
Storage
simplefunction.cpp
void void() { send func1;
read DONE; }
simplefunction.proxy.cpp
Proxy and stub names always match IDL file name

12. Demo program uses function w/no arguments
int main() {
func1() }
simplefunctionclient.cpp
CPU
Memory
Storage
CPU
Memory
Storage
rpcserver is generic main program…doesn’t depend on IDL or func1
void void() { send func1;
read DONE; }
simplefunction.proxy.cpp
int
Main() {
…loop accepting connections{
while(!eof){ dispatchFunction() } } }
rpcserver.cpp linked as simplefunctionserver

13. Demo program uses function w/no arguments
int main() {
func1() }
simplefunctionclient.cpp
CPU
Memory
Storage
CPU
Memory
Storage
void void() { send func1;
read DONE; }
simplefunction.proxy.cpp
…but we name the executable to match the particular use (simplefunctionserver)
int
Main() {
…loop accepting connections{
while(!eof){ dispatchFunction() } } }
rpcserver.cpp linked as simplefunctionserver

14. Demo program uses function w/no arguments
All stubs provide a dispatchFunction
int main() {
func1() }
simplefunctionclient.cpp
CPU
Memory
Storage
CPU
Memory
Storage
void void() { send func1;
read DONE; }
simplefunction.proxy.cpp
void dispatchFunction() { read from socket call __func1() }
void
__func1() {
read args from stream
call func1
send response
int
Main() {
…loop accepting connections{
while(!eof){ dispatchFunction() } } }
rpcserver.cpp linked as simplefunctionserver
simplefunction.stub.cpp

15. Demo program uses function w/no arguments
…that reads function names from the network and calls the right stub
int main() {
func1() }
simplefunctionclient.cpp
CPU
Memory
Storage
CPU
Memory
Storage
void void() { send func1;
read DONE; }
simplefunction.proxy.cpp
void dispatchFunction() { read from socket call __func1() }
void
__func1() {
read args from stream
call func1
send response
int
Main() {
…loop accepting connections{
while(!eof){ dispatchFunction() } } }
rpcserver.cpp linked as simplefunctionserver
simplefunction.stub.cpp

16. Demo program uses function w/no arguments
int main() {
func1() }
void func1() { return; }
simplefunctionclient.cpp
CPU
Memory
Storage
CPU
Memory
Storage
simplefunction.cpp
void void() { send func1;
read DONE; }
simplefunction.proxy.cpp
Response
DONE
Request
invoke func1()
void dispatchFunctiong() { read from socket call __func1() }
void
__func1() {
read args from stream
call func1
send response
int
Main() {
…loop accepting connections{
while(!eof){ dispatchFunction() } } }
rpcserver.cpp linked as simplefunctionserver
simplefunction.stub.cpp

17. Demo program uses function w/no arguments
int main() {
func1() }
void func1() { return; }
simplefunctionclient.cpp
You’ll be implementing proxies and stubs like these…first by hand…then using your RPC generator
CPU
Memory
Storage
CPU
Memory
Storage
simplefunction.cpp
void void() { send func1;
read DONE; }
Response
DONE
Request
invoke func1()
void dispatchFunctiong() { read from socket call __func1() }
void
__func1() {
read args from stream
call func1
send response
int
Main() {
…loop accepting connections{
while(!eof){ dispatchFunction() } } }
simplefunction.proxy.cpp
Interface definition file: simplefunction.idl
rpcserver.cpp linked as simplefunctionserver
simplefunction.stub.cpp

18. Demo program uses function w/no arguments
int main() {
func1() }
void func1() { return; }
simplefunction.proxy.cpp
&
simplefunction.stub.cpp
are provided for you as samples …
Yours will have to support other IDL files with functions that take arguments and return values!
simplefunctionclient.cpp
CPU
Memory
Storage
CPU
Memory
Storage
simplefunction.cpp
void void() { send func1;
read DONE; }
Response
DONE
Request
invoke func1()
void dispatchFunctiong() { read from socket call __func1() }
void
__func1() {
read args from stream
call func1
send response
int
Main() {
…loop accepting connections{
while(!eof){ dispatchFunction() } } }
simplefunction.proxy.cpp
Interface definition file: simplefunction.idl
rpcserver.cpp linked as simplefunctionserver
simplefunction.stub.cpp