{
  "nbformat": 4,
  "nbformat_minor": 0,
  "metadata": {
    "colab": {
      "name": "Install Scala in Colab.ipynb",
      "version": "0.3.2",
      "provenance": [],
      "private_outputs": true,
      "collapsed_sections": [],
      "toc_visible": true,
      "include_colab_link": true
    },
    "kernelspec": {
      "name": "python3",
      "display_name": "Python 3"
    },
    "accelerator": "GPU"
  },
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {
        "id": "view-in-github",
        "colab_type": "text"
      },
      "source": [
        "<a href=\"https://colab.research.google.com/gist/shadaj/323ad2393b46c1b71df435728a052c24/install-scala-in-colab.ipynb\" target=\"_parent\"><img src=\"https://colab.research.google.com/assets/colab-badge.svg\" alt=\"Open In Colab\"/></a>"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {
        "id": "zYzgRayyZ2z8",
        "colab_type": "text"
      },
      "source": [
        "# Scala Installer for Colaboratory\n",
        "This notebook installs [Almond](http://almond.sh), a Scala kernel for Jupyter, into Colaboratory and configures it to make the preinstalled Python libraries accessible to Scala code (through [ScalaPy](https://github.com/shadaj/scalapy)).\n",
        "\n",
        "Because this installer is built on Almond, you get complete Scala support inside your notebooks, including the ability to get code completions and access to the [Jupyter-specific APIs](https://almond.sh/docs/api-jupyter). In addition, this installer configures Almond to be able to load preinstalled modules in Colab such as `numpy` and `tensorflow` through ScalaPy.\n",
        "\n",
        "If coming to this notebook from GitHub, make sure to **not reset your runtime** when running this notebook. In order to install the Scala kernel, the installer writes data to the runtime filesystem, so resetting would clear out the kernel.\n",
        "\n",
        "## Post-installation Setup\n",
        "After installing the Scala kernel, you will need to **completely restart the Jupyter instance** for the Scala notebook you want to run. If you are not yet connected to a Jupyter server (check the top right of your screen), you are fine and can immediately start running code.\n",
        "\n",
        "However, if you previously started a Jupyter server, you must now go to `Runtime > Manage Sessions` and terminate the session for the Scala notebook. Then after reloading the page, you will see a button to connect to a server, which will start up a new Jupyter server that will now have the Scala kernel loaded.\n",
        "\n",
        "**Note:** if your session expires and the machine is shut down, you will need to re-run this installer because Colab resets the filesystem"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {
        "id": "QVJoUDPtb9gX",
        "colab_type": "text"
      },
      "source": [
        "Install the Almond kernel into the global Jupyter kernels."
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "id": "949yQj6ltEoW",
        "colab_type": "code",
        "colab": {}
      },
      "source": [
        "%%shell\n",
        "SCALA_VERSION=2.12.8 ALMOND_VERSION=0.3.0+16-548dc10f-SNAPSHOT\n",
        "curl -Lo coursier https://git.io/coursier-cli\n",
        "chmod +x coursier\n",
        "./coursier bootstrap \\\n",
        "    -r jitpack -r sonatype:snapshots \\\n",
        "    -i user -I user:sh.almond:scala-kernel-api_$SCALA_VERSION:$ALMOND_VERSION \\\n",
        "    sh.almond:scala-kernel_$SCALA_VERSION:$ALMOND_VERSION \\\n",
        "    --sources --default=true \\\n",
        "    -o almond-snapshot --embed-files=false\n",
        "rm coursier\n",
        "./almond-snapshot --install --global --force\n",
        "rm almond-snapshot"
      ],
      "execution_count": 0,
      "outputs": []
    },
    {
      "cell_type": "markdown",
      "metadata": {
        "id": "FXlAFUtPcEPo",
        "colab_type": "text"
      },
      "source": [
        "Finally, we modify the kernel definition to preload the Python 3 native library to enable usage of modules such as `numpy` and `tensorflow` in ScalaPy."
      ]
    },
    {
      "cell_type": "code",
      "metadata": {
        "id": "1kVqkjNBU6K6",
        "colab_type": "code",
        "colab": {}
      },
      "source": [
        "%%shell\n",
        "echo \"{\n",
        "  \\\"language\\\" : \\\"scala\\\",\n",
        "  \\\"display_name\\\" : \\\"Scala\\\",\n",
        "  \\\"argv\\\" : [\n",
        "    \\\"bash\\\",\n",
        "    \\\"-c\\\",\n",
        "    \\\"env LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libpython3.6m.so:\\$LD_PRELOAD java -jar /usr/local/share/jupyter/kernels/scala/launcher.jar --connection-file {connection_file}\\\"\n",
        "  ]\n",
        "}\" > /usr/local/share/jupyter/kernels/scala/kernel.json"
      ],
      "execution_count": 0,
      "outputs": []
    }
  ]
}