lec2

Mutex & Cond

• Cond broadcast/signal before unlock

Channel

• Channel blocks until both writing and reading side is ready.
• Start a go routine reading/writing the channel, then write/read the channel.

New and not New

One may construct an object via obj := Obj {}, or some constructor function NewObj() that returns an address of an object.

new(Type) returns an address of an object that has zero value. This serves as a default New* type constructor.

It is conventional to wrap a obj := Obj {} inside a New* type constructor and return its address.

RPC

semantics under failure:

• at-least-once: the rpc ensures that the procedure is executed at least once by the server. This does not align with most systems.
• at-most-once: the procedure is executed at most once by the server. This is the requirement of most systems.
• exactly-once: quite hard to implement, available under ideal circumstances.

So RPC are not identical to procedure calls.