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Vagrant based dev servers

Introduction

Follow "Setup procedure" below to quickly install a dev server on your computer, regardless of what operating system you are using. The procedure relies on Virtualbox, Vagrant and Fabric. Your working copy is on your computer, but it is shared with a virtual machine (VM) which actually renders the site.

History

A dev server requires a lot of software components to run properly, and it would be time-consuming to set them up manually. It is possible to make an automated (e.g. scripted) setup procedure, but it's not easy to support this capability on many different platforms. Hence we support one platform (Ubuntu) and expect that developers use a virtual machine if Ubuntu is not their primary operating system.

For some time, we provided dev servers as Virtualbox images, which were prepared by (manually) creating a VM with Ubuntu installed, and then running our setup script inside the VM. This worked well except that it was time-consuming to create these images (especially with chapter-specific databases and media files), and the files were very large (on the order of 5--10 GB) and time consuming to download. That is what motivated the development of an alternative setup process, where the VM is created and prepared on your machine (with few manual steps).

With this new procedure, we should be able to standardize the platform that all development and production servers use (currently it's Ubuntu 20.04) without tying developers to that platform.

Setup procedure

Preparation

The site VM is 64-bit Ubuntu, so it will probably not work if your computer runs a 32-bit operating system, although such computers are rare as of 2017.

On some computers, particularly Lenovo computers, you will need to enable hardware virtualization in the BIOS in order to run VMs. If you don't, this issue may manifest itself in Vagrant silently failing to boot your VM.

Base components

This setup procedure does have some prerequisites of its own, which you will need to install according to your own platform:

  • Git
  • Virtualbox
  • Vagrant (make sure you install the 64-bit version)
  • Python 2.7
  • Python libraries fabric and fabtools (can be installed using pip, which comes with Python; make sure to install version 1, not version 2 of fabric, so run pip install "fabric<2")

If you are on a Linux system, it's likely that everything can be installed using a package manager on the command line, e.g. by running sudo apt-get install git virtualbox vagrant python2 python-pip && sudo pip install fabric fabtools.

If you are on a Windows system, it's easiest if you install the PyCrypto binaries before trying to install Fabric. In addition, you should modify the PATH environment variable (the system one, not the user one) in Control Panel -> System -> Environment Variables... by append C:\Python27 and C:\Python27\Scripts, in order to put python, pip and fab on your PATH. (You may also want to append the path to the bin folder in your git installation for an SSH client.) You will need to restart Command Prompt after making this change. To append items to PATH, in Windows 10 you can edit Path and hit New to add new entries. In previous versions of Windows, you should add them to the end of your PATH, separated by semicolons. Finally, you may find that the Git Bash shell does not interact well with Fabric. The Windows Command Prompt works much better.

Installation

Using a shell, navigate to the directory where you would like to place the code (e.g. within your home directory), and check out our Git repository:

git clone https://github.com/learning-unlimited/ESP-Website.git devsite
cd devsite

If you already have a GitHub account with SSH keys set up, you may want to use git clone [email protected]:learning-unlimited/ESP-Website.git devsite to make it easy to push new code.

Next, use Vagrant to create your VM:

vagrant up

(If you get an error message suggesting that you run vagrant init, you probably forgot to cd devsite.)

Note that you will not be able to see the VM, since it runs in a "headless" mode by default.

The following command connects to the running VM and installs the software dependencies:

fab setup

The development environment can be seeded with a database dump from an existing chapter, subject to a confidentiality agreement and security requirements on the part of the developer. The preferred way to load a database dump is automatically over HTTP; this assumes you've been provided with a download URL. If you have, run the following command. (NOTE: Run only one of the next three commands. They are alternative ways to created the database.)

fab loaddb

You will be prompted to provide the URL. On future runs of fab loaddb, the database will be automatically reloaded from this URL. (If you mistype the URL, you can edit it by vagrant ssh-ing into the VM and editing /mnt/encrypted/fabric/dbconfig.)

Alternatively, the loaddb task accepts an optional argument to load a database dump in .sql or any other Potgres-supported dump format. If you've acquired a database dump, you can load a database by running the following, replacing /path/to/dump with the path to your database dump:

fab loaddb:/path/to/dump

Finally, you can set up your dev server with an empty database. At some point during this process, you will be asked to enter information for the site's superuser account.

fab emptydb

(If this step fails with an error "Operation now in progress", see the "Problems" section at the end.)

These commands can also be used on a system that has already been set up to bring your database up to date. They will overwrite the existing database on your dev server.

Now you can run the dev server:

fab runserver

Once this is running, you should be able to open a Web browser on your computer (not within the VM) and navigate to http://localhost:8000, where you will see the site.

Usage

The working copy you checked out with Git at the beginning contains the code you should use when working on the site. It has been shared with the VM, and the VM does not have its own copy of the code.

If you need to debug things inside of the VM, you can open your shell, go to the directory where you checked out the code, and run vagrant ssh.

  • The location of the working copy within the VM is /home/vagrant/devsite
  • The location of the virtualenv used by the VM is /home/vagrant/venv This is different from the conventional configuration (where the virtualenv is in an env directory within the working copy) so that the virtualenv is outside of the shared folder. This is necessary to allow correct operation if the shared folders don't support symbolic links. The virtualenv is loaded automatically when you log in to the dev server.

Usual workflow

Once you have everything set up, normal usage of your vagrant dev server should look something like this.

Before you start anything:

vagrant up

To run your dev server:

fab runserver

Other useful command examples:

fab manage:shell_plus
fab psql:"SELECT * FROM pg_stat_activity"

Once you're done:

vagrant halt

One last command! When your devserver gets out of date, this command will update the dependencies, run migrations, and generally make things work again:

fab refresh

If you want to add some custom shortcuts that don't need to go in the main fabfile, you can add them in a file called local_fabfile.py in the same directory as fabfile.py. Just add from fabfile import * at the top, and then write whatever commands you want.

For instructions on contributing changes and our git workflow, see contributing.rst.

Problems

  1. The vagrant up command errors out, or times out while waiting for the VM to boot. (You may also want to investigate some of these for errors later in the process.)

    If it errors out with a Ruby stack trace, there is a known issue with Vagrant/VirtualBox on IPv6 static networking.

    One other thing to try is to run the VM not headlessly. You can run the VM directly from VirtualBox. You can also do this in Vagrant by uncommenting the line # vb.gui = true in Vagrantfile, then running vagrant reload. VirtualBox may give a more helpful error message, or you may be able to observe the VM getting stuck waiting for a keypress that never comes, say on the bootloader.

    • If you have an older computer running a 32-bit operating system, then you might be out of luck since the VM runs 64-bit Ubuntu. Also check that you didn't install the 32-bit version of Vagrant.
    • Check that hardware virtualization is enabled in your BIOS, particularly if you're running a Lenovo computer.

  2. When running fab emptydb or fab loaddb, it fails with an error "Operation now in progress" OR with error "error 47 from memcached_mget: SERVER HAS FAILED AND IS DISABLED UNTIL TIMED RETRY".

    You need to restart memcached. First ssh into the VM with the command vagrant ssh, then run

    sudo service memcached restart

    Now try your fab command again.

  3. I forgot the passphrase for the encrypted partition.

    You won't be able to recover the data, but you can start over by dropping the tablespace encrypted and then re-running fab setup.

Some other common dev setup issues are discussed here.

Creating a new dev VM

Changes to the base VM should be needed very rarely, but you can't stay on the same Ubuntu version forever. Outline of steps used for the most recent upgrade:

  1. Find a Vagrant .box file for Virtualbox with the version of Ubuntu that you want. You might do this by downloading a publicly available one or by running sudo do-release-upgrade from an older base VM. Be sure to start from a base VM, not your current dev server with a database on it. If you start from a publicly available image, make sure to set the hostname to ludev and the username to vagrant.
  2. Run esp/update_deps.sh on the VM from step 1. This isn't strictly required but will make dev setup easier in the future, especially dev setup testing.
  3. Follow Vagrant's documentation to export the box you have to a .box file.
  4. Upload the .box file to S3. If you don't have access, ask someone.
  5. Update the Vagrantfile with the new VM's URL.

Upgrading your personal dev VM

If the base VM has been changed (see above), you will want to upgrade your development server. However, upgrading Ubuntu within a virtual machine can cause problems with your database. Therefore, you'll need to export your database, create a new virtual machine, then import your database:

  1. Make a copy of esp/esp/local_settings.py somewhere with a different name (e.g. on your desktop as "old_local_settings.py"). The original local_settings.py file will get overwitten by the end of this process and you will want to restore some of the settings from your previous VM setup.
  2. From within the "devsite" folder, run fab dumpdb. This action will save your database as a dump file in the devsite folder called devsite_django.sql. You can also specify a filename if you would like with fab dumpdb:filename.
  3. Run vagrant destroy (note: this destroys your virtual machine. Only do it once you are sure your database has been backed up and you are ready to continue).
  4. Now follow the VM installation instructions above, starting at vagrant up.
  5. After running fab setup, run fab loaddb:devsite_django.sql. If you specified a different filename when you dumped your database, use that name instead.
  6. Open your old local_settings.py file and your new local_settings.py file with a text editor. You will likely want to copy over most of your old local settings. The only thing that MUST remain from the NEW version is the NEW DATABASE PASSWORD.