Aug – Dec 2020

• I learnt about fundamentals of systems design while completing the projects for this class.

• Specifically, I learnt how to :
  • implement protocols for file transfer, using socket based API, between two multithreaded processes running on the same machine,
  • implement protocols for file transfer, using shared memory based API, between two multithreaded processes running on the same machine, and
  • implement remote procedure calls for file transfer in a distributed system.

• Tools used: C, Valgrind, C++, gRPC, Protobuf, POSIX C API for multithreading, shared memory and synchronization using semaphores

• Theory concepts learnt
  • Polices used by operating systems scheduler, such as,
    First Come First Serve, Shortest Job First, Round Robin
  • Memory managment techiques like
    Paging and segmentation as well as caching policy using Least Recently Used(LRU)
  • Virtualization concepts, models and techniques,
    Virtual Machine Monitor/ Hypervisor responsibilites, paravirtualization, OS protection rings and modes
  • Distributed File Systems and Distributed Shared Memory
    consistency models such as sequential and weak, file sharing semantics like session based and periodic updates
  • Cloud computing terminology
    Infrastructure as a Service like Amazon EC2, Platform as a Service like Google App Engine, Software as a Service like Gmail

Selected Figures

Figure 1: Flow of control diagram, between two processes using shared memory, to showing read-write sequence implemented using POSIX semaphores. Keyed off examples and notes here.

Figure 2: Flow of control (a)between a client and web proxy via sockets and (b) between web proxy and a cache server using shared memory. CMQ in the figure represents a central message queue using POSIX API. SHM refers to Shared Memory.

Figure 3: Flow of Control diagram for Store command used in simple distributed file system. Locking for files prevents concurrent writes.