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Pre-Requisites

Apps

  • As a DevOps engineer, you should be aware of the basics of programming and the software development lifecycle.

Compilers

  • Older compilers used to compile directly into machine code which was specific to a processor set. So, it could not be run on other machines.
  • Modern compilers convert to an intermediate code called as Byte Code which is then run by the interpreter (in case of interpreted languages)

Languages

Java

  • JDK (Java Development Kit) - tool to develop, build and run Java applications
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    • javac - used for compiling
    • javadoc - used for documentation
    • jdb - used for debugging
  • Java code compilation and execution process
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    • Source code is compiled into byte-code
  • Java Archive (JAR) is a packaging format to package multiple java .class files and dependent libraries into a single distributable package in .jar format.
    • jar cf MyApp.jar MyClass.class Service1.class Service2.class ... - to create a jar file
    • java -jar MyApp.jar - run a jar file
  • Web Archive (WAR) is a packaging format to package all the contents of .jar along with images and static contents required to build a web application.
  • JavaDoc is a tool to automatically generate documentation of the code
    • javadoc -d doc MyClass.java - generate documentation for the given java file
  • Java Application Build Process
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  • Application build process can be automated using Build Tools like Maven, Gradle & ANT. They use configuration files where we can specify build steps
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JavaScript / NodeJS

  • JavaScript was originally developed as a client side scripting language
  • NodeJS brought JS to the server side
  • NodeJS can handle a large number of concurrent connections by implementing a non-blocking IO model
  • Node Package Manager (NPM) is a package manager and repository of publicly available NodeJS packages
    • npm -v - get the NPM version
    • npm install serverless - install a package
    • npm install -g serverless - install a package globally
    • npm uninstall serverless - uninstall a package
    • npm search serverless - search a package
  • When importing a package in the code, node looks at the local node_modules folder under the application folder. If not found, it looks at the global node_modules directory. To see the list of paths node scans, run node -e "console.log(module.paths)"
  • Application dependencies are stored as configuration in package.json file at the root of the application directory.

Python

  • Server-side scripting language heavily used in Analytics
  • Both Python2 and Python3 can be installed on the system simulatneously
  • Pip Install Package (PIP) - package manager for Python
    • pip2 install numpy - python2
    • pip3 install numpy - python3
    • pip -V - check which python pip is pointing to
    • pip show numpy - show where a package is installed
    • pip install numpy --upgrade - version upgrade a package
    • pip uninstall numpy - uninstall a package
  • Application dependencies should be written in requirements.txt and installed by running pip install -r requirements.txt

Last updated: 2022-09-23