Distributed Systems

True or false? Distributed computing always follows a client-server architecture.

False

True or false? A client initiates an RPC call to a remote server but didn't receive a reply and times out. The client tries again and succeeds. In this, the client achieved exactly-once call semantic, just like a local function.

False

True or false? In RPC implementation, only the client program (the caller) needs the "stub" implementation of the remote function, not the server, because the function resides locally in the server and is called locally.

False

True or false? In pub/sub system, subscriptions mean subscribers specifying which events/message they are interested in sending their interests to known publishers.

False

True or false? View-synchronous communication in group communication refers to whatever messages are sent by a sender should be received by all group members exactly once, but not twice.

False

Which ones are true regarding descriptive models of distributed computing?

Fundamental model abstracts away details and only have entities and the interaction among them Architectural model describes roles and responsibilities of participating entities

Suppose you want to analyze the correctness and properties of a distributed computing problem. Which descriptive model you will take into account? Architectural models Fundamental models Physical models

Fundamental models

What is true regarding space-time coupling of remote invocation techniques?

Group communication is always space decoupled but may not be in time RPC is usually space-time coupled but can be decoupled in time, but not in space Publish-subscribe system is both time and space decoupled

In which way(s) message queues (MQ) differ from publish-subscribe (PS) systems

MQ allows point-to-point communication whereas PS enables one-to-many communication PS allows filtering and routing of messages based on message content, which MQ usually does not allow they both offer indirect communication but MQ mostly offers time decoupling whereas PS offers space decoupling

RPC (remote procedure call) semantic entails which of the following?

Marshaling of passed arguments (if any) Retransmission of results Retry request message Filtering duplicate requests

True or false? A channel-based subscription model in the publish-subscribe system is somewhat equivalent to a message queue between the publisher and subscriber.

True

True or false? A communication network itself is not a distributed system unless certain "applications" are running on it

True

True or false? In remote invocation, IDL (interface definition language) is designed to allow procedures implemented in different programming languages to invoke one another.

True

True or false? ZeroMQ, the messaging library, can implement a publish-subscribe system without any broker node.

True

RPC, as implemented in xmlrpc, is synchronous because

the caller calls the function and waits for the results to come before moving to the next step in the program

Transparency in distributed computing means

the collection of machines appears as one single machine in the eye of a client/user

Message queues are good for situations

when producers and consumer know from which queue they will write or read when a producer wants to connect to a certain consumer by both attaching to the same queue