Remote Procedure Calls Concepts
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Questions and Answers

Which technology was developed to standardize communication between distributed processes?

  • Sockets
  • Message Passing
  • Remote Procedure Call (RPC) (correct)
  • Network File System (NFS)

    • What is a primary goal of using Remote Procedure Calls (RPC)?

  • To manage network routing protocols
  • To allow clients to invoke procedures on remote machines as if they were local (correct)
  • To establish secure socket connections
  • To directly access memory on a remote machine

    • Which of the following is NOT a typical responsibility of an RPC implementation?

  • Sending parameters to the remote host
  • Returning results to the client
  • Connecting to the remote host
  • Managing the operating system's memory allocation (correct)

    • Why are calls by reference not typically possible in RPC?

    <p>Machines in a distributed system have different address spaces (D)</p> Signup and view all the answers

    What is a possible issue related to data representation that RPC implementations need to handle?

    <p>Byte ordering differences (Big Endian vs. Little Endian) (A)</p> Signup and view all the answers

    What paradigm does RPC help implement?

    <p>Request-Reply Paradigm (D)</p> Signup and view all the answers

    Which transport layer protocols do sockets directly interface with?

    <p>TCP and UDP (A)</p> Signup and view all the answers

    What does a socket represent in the context of network communication?

    <p>A logical door between an application process and the transport protocol. (C)</p> Signup and view all the answers

    If a server application is listening on port 443, what service is it MOST LIKELY providing?

    <p>HTTPS (A)</p> Signup and view all the answers

    In a typical RPC interaction, what is the immediate action a client takes after sending a request?

    <p>Waits for the server's response (A)</p> Signup and view all the answers

    Which of the following best describes an 'at most once' RPC execution?

    <p>The client will attempt the RPC only once, and will not retry if it fails. (C)</p> Signup and view all the answers

    What distinguishes 'at least once' RPC execution from 'at most once'?

    <p>'At least once' retries the RPC until acknowledgment is received, while 'at most once' does not. (D)</p> Signup and view all the answers

    What is a key characteristic of an 'idempotent' RPC?

    <p>It can be repeated without changing the outcome. (C)</p> Signup and view all the answers

    What is the primary encoding format used by XML-RPC?

    <p>XML (D)</p> Signup and view all the answers

    How does JSON-RPC differ from XML-RPC regarding data format?

    <p>JSON-RPC uses JSON, XML-RPC uses XML. (C)</p> Signup and view all the answers

    Which feature is unique to JSON-RPC, compared to XML-RPC, as mentioned in the document?

    <p>Support for notifications and out-of-order responses. (C)</p> Signup and view all the answers

    According to the content, which is considered an advantage of JSON over XML?

    <p>JSON is easier to parse and is less verbose. (B)</p> Signup and view all the answers

    Which of the technologies was actively used for the shortest period in total, according to the content?

    <p>Java RMI (A)</p> Signup and view all the answers

    What is the primary function of a client stub in a Remote Procedure Call (RPC)?

    <p>To act as a gateway for distributed system objects, handling outgoing requests and network logic. (D)</p> Signup and view all the answers

    Which process involves transforming the memory representation of an object into a format suitable for transmission?

    <p>Marshalling (B)</p> Signup and view all the answers

    What is a key reason for using a buffer in both user space and kernel space when performing system calls?

    <p>To minimise the number of slow system calls. (D)</p> Signup and view all the answers

    In the context of RPC, what is 'unmarshalling'?

    <p>The process of converting transmitted data back into its original format. (D)</p> Signup and view all the answers

    What distinguishes marshalling from serialization in more complex languages like Java?

    <p>Marshalling considers the location of object class definitions and treats remote objects differently, while serialization doesn't. (B)</p> Signup and view all the answers

    Which of the following is NOT a potential cause of failure in a Remote Procedure Call (RPC)?

    <p>The server receives the request but does not perform the requested action. (C)</p> Signup and view all the answers

    What is meant when a Remote Procedure Call (RPC) exhibits 'exactly once' success mode?

    <p>The RPC will execute only once, without under or over execution. (A)</p> Signup and view all the answers

    What was the initial purpose of SOAP when it was designed in 1998?

    <p>To function as an Object Access protocol. (D)</p> Signup and view all the answers

    Immediately before the client stub makes a system call to send a message in the context of an RPC, what action occurs?

    <p>The client stub packs the parameters into a message. (B)</p> Signup and view all the answers

    Which of the following is NOT a core characteristic of SOAP?

    <p>Fixed messaging roles, always requiring an Enterprise Service Bus. (D)</p> Signup and view all the answers

    Which of these best describes the role of a system call in transition from user space to kernel space?

    <p>A mechanism that facilitates a slow operation during the transition. (B)</p> Signup and view all the answers

    What is the primary purpose of the SOAP extensibility model?

    <p>To allow alterations to the processing model using new information in the header. (A)</p> Signup and view all the answers

    Based on the provided content, where is marshalling used besides RPC?

    <p>.NET framework and the Mozilla Application Framework (B)</p> Signup and view all the answers

    Which of these is a necessary part of an extension to the SOAP framework?

    <p>A URI to name the feature being introduced. (D)</p> Signup and view all the answers

    In the context of SOAP when combined with HTTP and not using Web Services Addressing, what is a limitation described?

    <p>The roles of interacting parties are fixed. (A)</p> Signup and view all the answers

    What is the primary benefit of SOAP's neutrality characteristic according to the text?

    <p>It facilitates SOAP to be used with any transport protocol. (D)</p> Signup and view all the answers

    In SOAP, what is the purpose of the information included in messages due to an extension?

    <p>To enable the extension by providing necessary data for all nodes. (A)</p> Signup and view all the answers

    Which of these best describes the ultimate goal of SOAP's original design?

    <p>To create a format adaptable to any operating system, language, or platform. (B)</p> Signup and view all the answers

    In Java RMI, what is the primary role of a 'stub' object?

    <p>To act as a local proxy, handling message marshalling and delivery. (C)</p> Signup and view all the answers

    What is the main reason why standard Java object passing semantics do not work directly in RMI?

    <p>Because remote objects' references cannot be directly accessed by a Java application, they need to exist in the same JVM. (B)</p> Signup and view all the answers

    What is primarily achieved using Java object serialization?

    <p>Converting the object into a byte stream representation for transfer. (C)</p> Signup and view all the answers

    Which of the following would be a valid use case for SOAP, in contrast to alternatives like REST?

    <p>Complex, secure financial transactions requiring coordination and transaction management. (A)</p> Signup and view all the answers

    In the context of Java RMI, what mechanism is used to actually transmit objects?

    <p>Java Serialization, byte stream. (B)</p> Signup and view all the answers

    Which of the following statements is true regarding the use of Java Serialization in RMI?

    <p>Objects that implement the <code>Serializable</code> interface, and/or <code>Remote</code> interface, can be converted to a byte stream and transferred over the network. (D)</p> Signup and view all the answers

    What is the primary purpose of defining an interface (such as RMIInterface) in Java RMI?

    <p>To specify the methods that can be called remotely on the remote object. (A)</p> Signup and view all the answers

    What is the role of Naming.rebind in the Java RMI server example provided?

    <p>To register the remote object with a registry so that it can be looked up by clients. (B)</p> Signup and view all the answers

    What is the significance of the transient keyword in the given Java serialization example for theunInterestingLongLongList?

    <p>It indicates that the field is not meant to be included in the serialization process. (A)</p> Signup and view all the answers

    What is the purpose of the UnicastRemoteObject class in the Java RMI server code?

    <p>To make the server object available for remote method invocation. (B)</p> Signup and view all the answers

    What technology does gRPC primarily use for its interface definition language?

    <p>Google Protocol Buffers. (A)</p> Signup and view all the answers

    Which of the following best describes Protocol Buffers?

    <p>A framework for serializing structured data that is smaller, faster and simpler than XML. (B)</p> Signup and view all the answers

    Which of the following technologies provides 'soft versioning' to allow interface and data type evolution across teams?

    <p>Apache Thrift. (C)</p> Signup and view all the answers

    In Apache Thrift, what is the role of code generators?

    <p>To automatically generate interface related code for different languages. (C)</p> Signup and view all the answers

    Which concept does gRPC utilize to serialize data before transmitting it over the network?

    <p>Protocol Buffers. (D)</p> Signup and view all the answers

    Study Notes

    RPC RMI SOAP

    • RPC (Remote Procedure Call) was introduced to improve communication between distributed processes, making it more uniform, reusable, and user-friendly.
    • Early RPC implementations, such as Sun's RPC, were used with the Network File System (NFS).
    • RPC technologies allow users to call functions on different physical machines as if they were local processes.

    Introduction

    • When distributed systems use processes to pass messages, these messages frequently contain only basic data.
    • Interpretation of the message must be agreed upon between the sender and receiver.
    • This makes it difficult to reuse components and promote interoperability between systems.

    Review: Sockets

    • A socket is an API (Application Programming Interface) that functions as a "door" between application processes and end-transport protocols.
    • This permits application processes to communicate across a network.
    • Applications using sockets utilize a protocol controlled by the operating system (OS), abstracting communication details from application developers.

    Review: Sockets and Ports

    • Sockets are assigned a free port by the operating system.
    • Each process on a network can be identified through its listening port number.
    • TCP and UDP ports function independently.
    • Default server-side application ports are standardized (e.g., HTTP: 80, HTTPS: 443, SMTP: 25).

    RPC Procedure

    • RPC is a request-response protocol.
    • A client initiates a procedure by sending a request message to a remote server.
    • The request message includes parameters for the function to be executed.
    • The remote server executes the specified function and sends a response message back to the client.
    • The client waits for the response (synchronous request) until the reply is received.

    RPC Events

    • The client contacts the client stub. Parameters are usually pushed onto the stack.
    • The client stub marshals the parameters into a message.
    • The client's operating system sends the message to the server.
    • The server's operating system sends the message to the server stub.
    • The server stub unpacks (unmarshalls) the parameters.
    • The server stub calls the remote procedure.
    • The reply uses the same methodology in reverse.

    Compilation

    • The compilation process involves generating server and client stubs, using the interface specification.
    • Common headers and the RPC library are also involved.

    RPC Stub

    • The stub acts as a gateway for distributed system objects.
    • All outgoing requests to server-side objects are routed through the stub.
    • Includes network logic to ensure reliable communication between the client and server.
    • Responsible for initiating communication, handling marshalling/unmarshalling of messages, and informing the server about the procedure call.

    Marshalling

    • Marshalling transforms an object's in-memory representation into a format suitable for storage or transmission.
    • Parameters in an RPC call are marshaled before being sent to the remote procedure.
    • Marshalling is used in .NET and Mozilla Application Framework.

    Marshalling Example

    • Transitioning between user and kernel space often involves system calls.
    • Minimizing system calls by maintaining a buffer in user and kernel space enhances performance.
    • Commands waiting for execution are marshaled into the user space buffer.
    • When the buffer nears emptiness, a system call is performed to transfer commands to kernel space.

    Marshalling VS Serialisation

    • In Python, marshalling and serialization are often treated as identical.
    • In Java, marshalling involves recording codebases, differing from simple serialization.

    RPC Failures

    • Distributed systems, like RPC components, are susceptible to various failure types.
    • Determining the root cause of an RPC failure can be complex.
    • RPC failures might stem from lost replies, server crashes before starting, unreachable servers, or client crashes before response.

    RPC Success Modes

    • Exactly Once: Guarantees the procedure executes only once, no more or less. Complex implementation.
    • At Most Once: Permits the procedure to be executed at most once. Not suitable for all situations.
    • At Least Once: The operation executes the procedure repeatedly until an acknowledgment is received, overcoming potential lost acknowledgments.

    XML-RPC

    • XML-RPC utilizes XML to encode calls and as its transport mechanism.
    • Multiple parameters and a single result can be sent through its calls.
    • Parameters frequently use various data types, potentially more complex ones like array of integers.

    JSON-RPC

    • JSON-RPC is similar to XML-RPC, but uses JSON instead of XML.
    • It supports notifications, which are calls to the server not requiring a response, and allows multiple calls with potentially out-of-order responses.

    XML vs JSON

    • XML is more verbose and difficult to parse than JSON.
    • JSON represents data as a map, rather than a tree.
    • XML-RPC has faced criticism due to its verbosity in recent years.

    Communication Over the Years

    • Presents a summary of various communication protocols and their respective timeframes

    What do developers want?

    • Developers prefer more application development and less communication overhead.

    Simple Open Access Protocol (SOAP)

    • SOAP was initially an Object Access Protocol in 1998.
    • Designers focused on lightweight XML messaging compatible with various operating systems and platforms.
    • It also promoted access to remote objects through non-HTTP traffic.

    SOAP Characteristics

    • Extensible: Extends the existing protocol with features like security and addressing.
    • Neutral: Adaptable to various transport protocols (e.g., HTTP, SMTP, TCP, UDP, JMS).
    • Independent: Uses any programming model.

    SOAP Processing Model

    • Describes the various steps in SOAP processing, including the use of HTTP, TCP, MSMQ and SMTP.

    SOAP Extensibility Model

    • Designed to allow extensions to its framework for altered processing models, with the inclusion of reliability, security, routing, and the like.
    • Extensions require a URI, node-specific information, and implementation details, including handling communication failure and information transfer.

    SOAP Envelope Example

    • Provides code example showing different SOAP header elements.

    SOAP Advantages and Disadvantages

    • SOAP's advantage is its protocol neutrality, making it flexible to be used with various methods.
    • However, reliance on HTTP and its use of verbose XML make it slow.

    Modern SOAP Usage

    • Though other protocols like REST are now widely used, SOAP is still useful where ACID transactions and robust security are needed, such as within WS-Security, WS-Transactions, and WS-Coordination.

    Remote Method Invocation (RMI)

    • RPC does not directly provide abstraction of object transfer, as RMI does.
    • Java's RMI enables direct transfer of serialized classes, with support for garbage collection.
    • Implementing the Remote or UnicastRemote interface is needed to convert objects into remote objects.

    Java Remote Objects

    • Remote objects are equivalent to local objects in Java.
    • References identify objects; applications don't possess remote object references.
    • A proxy object, called a stub, is representative locally.
    • The stub handles marshalling messages and delivers them to the remote object.

    Remote Method Invocation

    • Describes process with diagrams (Client and Server, relationships between Object A, Object R, stub, proxies and RMI registry).

    RMI Passing By Reference

    • Values in Java are passed by reference. This is a challenge for RMI, where objects must be passed and transferred efficiently.
      • Java uses serialization to transfer objects across the network in an appropriate format.

    Java Serialisation

    • The process of converting an object into a byte stream, including class, member variable, and variable values.
    • This enables the recreation of the target object after transfer across a network (e.g., to another computer).

    Java Serialisation Example

    • Provides code examples for serialisation with data structures.

    Java RMI Remote Interface Example

    • Demonstrates the structure of a Java RMI remote interface (defines methods for remote calls).

    Java RMI Server Example

    • A code example showcasing a Java RMI server implementation.

    Java RMI Client Example

    • A code example showcasing a Java RMI client implementation.

    Apache Thrift

    • Created by Facebook, now an Apache project, with a simple interface definition language (IDL).
    • Offers optimized serialization.
    • Supports various languages with code generators for glue code.
    • Soft versioning allows for interface/data type evolution.

    Apache Thrift

    • This section shows diagrams of Thrift client-server interaction, highlighting protocol layers and code generation process.

    gRPC

    • Developed by Google in 2015, using Protocol Buffers for interface description language.
    • Protocol buffers are known for their streamlined, efficient, and automated serialization mechanisms.
    • Smaller structure than XML.

    Google Protocol Buffers

    • Shows examples of Google Protocol Buffer structure (message definitions for types like Person and PhoneNumber).

    Google Protocol Buffers

    • Provides examples of code usage for data serialization.

    gRPC

    • Describes diagrams showing gRPC client-server request/response flow via protocol buffers, including different client types (Ruby, Android-Java).

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    Related Documents

    RPC RMI SOAP Presentation PDF

    Description

    This quiz covers essential concepts related to Remote Procedure Calls (RPC), focusing on their implementation, characteristics, and related networking protocols. Test your understanding of how RPC standardizes communication between distributed processes and the challenges that may arise during this interaction.

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