ch.4

Question 1

what are the issues with soft modularity?

Answer 1

1. caller and callee share a memory
   - write to something its not suppose to
   - arbitrary access to state (no boundaries)
   - buffer overflow attacks
2. caller and callee share an interpreter
   - no control over runaway modules (propagation of effects)
   - no module level permission (modules can delete its entire self)
   - cannot mange permissions
   - modules share fate (prop of effects)

Question 2

what are the advantage of a client server model?

Answer 2

1. don’t rely on shared state
2. many errors cannot propagate as requests are marshaled
3. can limit the time it waits for a response ( no infinite loops)
4. only communicate using messages, so it encourages well-defined interfaces

Question 3

what are two challenges of a client server mode?

Answer 3

1. improper timeouts could lead to a functions running too many times (server needs enough time to process requests)
2. the server could fail to send back a request

Question 4

what are remote procedure calls? (RPC)

Answer 4

a protocol that one program can use to request a service from a program located in another computer on a network without having to understand the network’s details

Question 5

what is idempotence?

Answer 5

doesn’t change the state of the program, side effect free & can be executed multiple times

Question 6

synchronous RPC

Answer 6

the client is forced to wait for the server before proceeding with further actions

Question 7

asynchronous RPC

Answer 7

the server can perform tasks while the client also performs tasks