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Distributed Systems CS 15-440

Distributed Systems CS 15-440. Project 1: File Storage and Access Kit ( FileStack ) Recitation 1 , Aug 29, 2013 Dania Abed Rabbou and Mohammad Hammoud. Logistics. Solo project Programming Language: Java Design Document Due Date: Sept. 9, 2013 Project Due Date: Sept. 25, 2013

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Distributed Systems CS 15-440

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  1. Distributed SystemsCS 15-440 Project 1: File Storage and Access Kit (FileStack) Recitation 1, Aug 29, 2013 Dania Abed Rabbou and Mohammad Hammoud

  2. Logistics • Solo project • Programming Language: Java • Design Document Due Date: Sept. 9, 2013 • Project Due Date: Sept. 25, 2013 • Q&A: Piazza, Office Hours, & Appointments

  3. Learning Objective • Apply the knowledge of client-server communication and Remote Method Invocation (RMI) to build a Distributed File System (DFS)

  4. Distributed File System (DFS) • Why File Systems? • To organize data (as files) • To provide a means for applications to store, access, and modify data • Why Distributed File Systems (DFSs)? • Sharing and managing data in distributed systems • Big data continues to grow • A DFS can hold sheer volumes of data (contrary to a local file system) and provide access to these data to many clients dispersed across networks

  5. Entities & Architecture • Storage Servers (SSs) • Each SS stores files in its local file system (in a temporary directory) • Naming Server (NS) • NS stores metadata, which mapsfiles to storage servers (much like DNS) • Clients • Perform operations on files (e.g., list, read, write etc.) • Architecture • Based on client-server architecture

  6. Client Operations • Operations on files/directories: • CreateFile, CreateDirectory, Read, Write, Size, List, Delete, IsDirectory • Auxiliary operation: • getStorage • Ideally, SSs must handle all file operations • In our case, NS handles some, to maintain integrity and reduce communication overhead

  7. Communication (3) CreateFile, CreateDirectory, IsDirectory, Delete, List, GetStorage (1) Registration (4) Results, Storage Server (2) Duplicate Files, Create, Delete (5) Read, Write, Size (6) Results Request-Reply Communication Paradigm

  8. Communication via Sockets • A Socket is an end-point of communication that is identified by an IP address and port number • A client sends requests to a server using a client socket • A server receives clients’ requests via a listening socket

  9. Communication via Sockets (cont’d.) Service Socket Listening Socket Client Socket

  10. Implicit Communication using RMI • We refer to the act of “performing an operation” as “invoking a method” • RMI library makes remote method invocations appear to be local method invocations abc RMI’s Provided Transparency Storage Server Local File System Network P Read”abc” Read”abc” Client Data Data Client P RMI’s Reality

  11. Stubs and Skeletons invoke implementer method SKELETON YES NO Is read defined in the remote Interface? invoke implementer method STUB Stub.read(“abc”)

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