Adapting codes to IMAS - Adapting codes to IMAS based Docker (22.09)

1.1. Introduction

• Docker is a tool which allows to start containers i.e. lightweight, isolated environments (OS, libraries, configurations)

  • You can install Docker for Mac, Windows or Linux: documentation

• To work with a container you need an image to start from

• Images can be found in public or private repositories:

  • Base operating systems e.g. Ubuntu or CentOS
  • Ready-to-start interpreters e.g. Python or PHP
  • Database management systems e.g. MySQL or PostgreSQL

• A container executes one or more processes in its isolated environment

• The process might be a daemon e.g. Apache HTTP Server or it can be an interactive terminal

• Dockerization advantages:

  • Quick prototyping and testing

    • For example, you can easily spawn multiple versions of PostgreSQL and test your SQL queries against them

  • Better dissemination

    • The product owner can share a Docker image and anyone interested can use it straight away

  • Enhanced security

    • A container is isolated and runs a limited number of processes
    • Even if it gets hacked, the rest of the system remains unharmed

  • Easier maintenance

    • The images are usually built in an automatic way via CI/CD pipelines or regularly scheduled jobs
    • No matter how complex the environment is, once the image recipe is created all interested users can instantiate containers at will

1.2. IMAS Docker

• The IMAS environment is available under a few flavors

• The most important is imas/ual, which contains Data Dictionary and Access Layer

• The images are available in a private Docker registry https://rhus-71.man.poznan.pl, which requires logging in first:

  docker login rhus-71.man.poznan.pl
  

1.2.1. Interactive session

• To pull the image:

  docker pull rhus-71.man.poznan.pl/imas/ual
  

• To tag the image with shorter name:

  docker tag rhus-71.man.poznan.pl/imas/ual imas/ual
  

• To begin an interactive session:

  docker run -it imas/ual
  

  • -it stands for --interactive and --tty, which allows to establish the session

1.2.2. Running codes in the container

• A collection of simple IMAS codes to start with can be found here: https://github.com/tzok/imas-hello-world
• The examples cover C++, Fortran, Java and Python
• All codes create the summary IDS in shot=1 and run=1, each with a different value in the comment field
• There is a helper Python script python/read.py which allows to verify correctness of those codes

1.2.2.1. C++

Source code of cpp/hello.cpp:

#include <UALClasses.h>
#include <pwd.h>
#include <unistd.h>

int main() {
    uid_t uid = geteuid();
    struct passwd *pw = getpwuid(uid);

    IdsNs::IDS ids(1, 1, 0, 0);
    ids.createEnv(pw->pw_name, "test", "3");

    ids._summary.ids_properties.comment = "Hello World from C++";
    ids._summary.ids_properties.homogeneous_time = 1;
    ids._summary.time.resize(1);
    ids._summary.time(0) = 0.1;
    ids._summary.put();

    ids.close();
    return 0;
}