P4L1 - Remote Procedure Calls

Question 1

What is the purpose of RPC?

Answer 1

• To remove boilerplate
• To hide cross-machine complexities
• To decouple the communication protocol from the procedure-call logic. (You can focus on what the cross-machine function does and not how it communicates)

Question 2

List the benefits of RPC

Answer 2

1. Offers a high-level interface for data movement and communication
2. Handles a lot of the errors that may arise from low-level communication/transmission interactions
3. Hides complexities of cross-machine interactions

Question 3

T/F: By default, RPCs have asynchronous call semantics

Answer 3

False, RPCs have synchronous call semantics

Question 4

T/F: RPC is meant to be more than a transport-level protocol and it should support different types of protocols (UDP,TCP or others)

Answer 4

True!

Question 5

Describe the high level structure of RPC

Answer 5

Client sends a request to perform some operation which the server has implemented. Server calls implementation of the operation and returns the result to the client

Question 6

Describe steps of RPC

Answer 6

1. Register - server “registers” procedure, arg types, location…
2. Bind - Client finds and “binds” to the desired server
3. Call - Client makes RPC call; control passed to client stub
4. Marshall - Client stub “marshals” arguments into buffer
5. Send - Client sends messages to server
6. Receive - Server receives message; passes to server-stub
7. Unmarshal - Server stub unmarshals the args
8. Actual Call - Server stub calls local procedure
9. Result - Server performs operation and computes result

Question 7

T /F: When using RPC, the client and server don’t need to be developed together

Answer 7

True!

Question 8

RPC systems rely on the use of ____ ____ ____ which serve as a protocol of how the client-server agreement will be expressed

Answer 8

Interface Definition Languages (IDL)

Question 9

T/F: An RPC system can use an IDL that is language-agnostic

Answer 9

True

Question 10

What is the purpose of the IDL

Answer 10

It is used to define the interface. It helps the RPC system generate stubs and to generate information that is used in the service discvoery process

Question 11

T/F: The IDL is used for the implementation of the service

Answer 11

False!

Question 12

_____ is the mechanism used by the client to determine which server to connect to, based on the service name and the version number

Answer 12

Binding

Question 13

To support binding, there needs to be some systems software that maintains a database of all available services, known as ____

Answer 13

registry

Question 14

A registry is essentially the _____ _____ for the services

Answer 14

yellow pages

Question 15

T/F: Pointers are able to be used in RPC

Answer 15

If configured, the REFERENCED data can be copied instead of the pointers during marshalling

Question 16

How are partial failures handled in RPC?

Answer 16

RPC incorporate a special error notification that tries to capture what went wrong with an RPC request

Question 17

What is SunRPC?

Answer 17

RPC package developed by Sun for UNIX systems

Question 18

List the design choices of the SunRPC

Answer 18

1. One registry per machine
2. Language-Agnostic IDL known as XDR
3. Allows use of poitners
4. Has mechanisms for dealing with errors

Question 19

The server specifies the interface that it supports in a ____ file for SunRPC

Answer 19

.x

Question 20

What is the name of the registry process that runs on every machine with SunRPC

Answer 20

portmapper

Question 21

What is another popular RPC system other than SunRPC

Answer 21

Java RMI - Java Remote Method Invocation