Sunday, August 25, 2019

One upgrade to rule them all

Up to now, the way of updating dbdeployer was the same as installing it for the first time, i.e. looking at the releases page, downloading the binaries for your operating system, unpacking it and finally replacing the existing binaries.

This is not the procedure I follow, however, as for me updating means just compile the latest version I have just finished coding. For this reason, when Simon Mudd mentioned to me that dbdeployer should update itself over the Internet, I didn’t immediately grasp the concept. But then he talked to me again, and he even coded a sample script that does what he suggests: look for the latest release, download it, and replace the current executable with the latest one.

The only problem with that approach is that dbdeployer should then be distributed with one binary and one update script (and we should make sure that more tools such as curl and gunzip are available in the host computer), while I have pushed the concept that the binary executable should be the only thing needed. Thus I spent a few hours converting the script ideas into dbdeployer internal workings, and given that it had already all the components in place (such as downloading files from the internet and unpacking them) it was done quickly. As a result, dbdeployer can now look online for newer versions of itself, and get its own replacement painlessly.

The new functionality is dbdeployer update, which works almost silently to do what you expect, if the version online is higher than the local one, and protects you against accidentally fetching an outdated version or binaries from the wrong operating system.

This is the last update that you need to do manually. After that, the next ones can be fetched directly with dbdeployer itself.

The new command has several options, mostly added for the advanced user:

$ dbdeployer update -h
Updates dbdeployer in place using the latest version (or one of your choice)

  dbdeployer update [version] [flags]


$ dbdeployer update
# gets the latest release, overwrites current dbdeployer binaries

$ dbdeployer update --dry-run
# shows what it will do, but does not do it

$ dbdeployer update --new-path=$PWD
# downloads the latest executable into the current directory

$ dbdeployer update v1.34.0 --force-old-version
# downloads dbdeployer 1.34.0 and replace the current one
# (WARNING: a version older than 1.36.0 won't support updating)

      --OS string           Gets the executable for this Operating system
      --docs                Gets the docs version of the executable
      --dry-run             Show what would happen, but don't execute it
      --force-old-version   Force download of older version
  -h, --help                help for update
      --new-path string     Download updated dbdeployer into a different path
      --verbose             Gives more info

The option that would also benefit casual users is --dry-run, as it shows which release it would get the executable from, without actually changing anything.

You may ask: why would I want to update using an older version? Although at first sight is not a sound idea, there are at least two reasons for that:

  1. there was a bug in the latest release. It isn’t an uncommon occurrence, and much as I would like to claim my code is bug free, I know that’s a pipe dream. So, if a bug is found that affects your workflow, a safe course of action is getting the previous release.
  2. From time to time, I publish experimental releases out of a branch. You may want to try them out, and then go back to the comfort of the latest non-experimental one.

If you don’t know what the releases contain, you can look them up without using a browser, with the command dbdeployer info releases. For example:

$ dbdeployer info releases latest
Remote version: v1.36.1
Release:        dbdeployer 1.36.1
Date:           2019-08-18T13:23:53Z

- Fix a bug in 'dbdeployer update': it only worked with --verbose enabled
- Fix output of 'dbdeployer update': it now confirms that the update has

 dbdeployer-1.36.1-docs.linux.tar.gz (5.9 MB)
 dbdeployer-1.36.1-docs.osx.tar.gz (6.1 MB)
 dbdeployer-1.36.1.linux.tar.gz (5.8 MB)
 dbdeployer-1.36.1.osx.tar.gz (5.9 MB)

There is another feature that complements dbdeployer update: it’s the ability of setting up command line completion for dbdeployer.

$ dbdeployer defaults enable-bash-completion -h
Enables bash completion using either a local copy of or a remote one

  dbdeployer defaults enable-bash-completion [flags]

      --completion-file string   Use this file as completion
  -h, --help                     help for enable-bash-completion
      --remote                   Download from GitHub
      --remote-url string        Where to downloads from (default "")
      --run-it                   Run the command instead of just showing it

This command retrieves the latest completion file, and helps you to install it in the right position. By default, it gets the file and doesn’t change anything in your bash_completion directory: it tells you what commands to run. You can let it do the copying (which may require sudo access) using --run-it.