OmbuLabs Blog

The Lean Software Boutique

Articles about Open Source

Announcing AfipBill

If you live in Argentina and you ever use AFIP, you should already know that their platform is not the best in terms of user friendliness. We wanted to integrate OmbuShop with AFIP (using their API) in order to generate and print the bills for each seller. Unfortunately, there is no way to do this because the API doesn't generate a printable version (PDF) of the bill.

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Introducing Pecas: Dashboards for Freckle

At Ombu Labs we are big fans and happy customers of Freckle. We use their widget to track all the hours that we spend on client projects, open source development, and our own products.

Today I'm happy to introduce Pecas, time tracking leaderboards for Freckle! Pecas is an open source tool that integrates with your account and generates beautiful leaderboards per project and per teammate.

Here is a sample dashboard for all your projects:

A sample leaderboard in the Pecas web interface

On top of that, it will send you an email alert if you haven't tracked any hours during a work day. If it's a holiday, it won't bother you. :)

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Introducing Infractores

I've always been a big fan of scratching your own itch. My latest itch was the insane amount of parking violations that I see everyday in Buenos Aires, near our office.

We decided to build a simple tool that would allow anyone with a Twitter account to report a parking violation. All you need to do is submit a geolocated tweet and a couple of photos (as evidence!)

Here is an example:

You can check out this tool over here: http://www.infractoresba.com.ar

This page shows all the parking violations reported by users to @InfractoresBA or with the #InfractoresBA hashtag. It's as simple as that.

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Protect your sensitive data in Git

If you are working with open source or if you are going to open source a repository, you should ensure that none of your sensitive data (API Keys, Credentials, Passwords) can be accessed by anyone.

One thing that a lot of people forget, is that this information stay forever in your repository history, if you do not rewrite the history of your repository.

For instance, what usually happens is that you commit a file with sensitive information. In this Example I added accidentally my ssh-key to the repo:

$ git commit -am 'init git repo'
[master (root-commit) 917a1e1] init git repo
 2 files changed, 52 insertions(+)
 create mode 100644 id_rsa
 create mode 100644 id_rsa.pub

After doing a couple of additions, working and editing, I realise that I should never have commited the ssh-key. *facepalm*

Alright, then I just do a simple git rm --cached id_rsa and everything is back to normal. I also add this file to a .gitignore, so that this cannot happen in the future anymore.

(master) $ git rm --cached id_rsa
rm 'id_rsa'
(master) $ git status
A  .gitignore
D  id_rsa
(master) $ git commit -am 'remove id_rsa'
[master c69deb9] remove id_rsa
 2 files changed, 1 insertion(+), 51 deletions(-)
 create mode 100644 .gitignore
 delete mode 100644 id_rsa

So if we now have a look in our commit list, we can still see our first commit where I added my ssh-key. If I checkout this commit, I still have the contents of my ssh-key available.

(master) $ git log
917a1e1 - init git repo (24 minutes ago) <Sirko Sittig>
(master) $ git checkout 917a1e1
((detached from 917a1e1)) $ cat id_rsa
-----BEGIN RSA PRIVATE KEY-----
MIIJKQIBAAKCAgEAoequrqsM42na3OpvBFYOpqvzJumr3/kxJTuluXbPyJzVjMXf
d/uhFUJgSqq4AJGOFLLPpQ+9jwfA+WraIxZ9R7p8LgpNdUwKsmGnUvofeD/9Rs1y
YZO8EAjl1URLJ379nN+L5KKPS/48Q4iGp57iwuGzrXLHccLyW5+Z0iMuHlKBQzPx
...

To ensure that ALL of this data gets properly removed, I need to remove this file from all the commits in the repository with git filter-branch. The command git rm --cached git rm docs is not sufficient in this case.

(master) $ git filter-branch --tree-filter 'rm -f id_rsa' HEAD
Rewrite c69deb9779a30e6335ab1a8ac1a0825cfc9302e4 (6/6)
Ref 'refs/heads/master' was rewritten

So far so good, but what about my other branches that have been created? bash (master) $ git checkout new-feature (new-feature) $ ls drwxrwxr-x 3 sirko sirko 4096 Dec 31 13:20 ./ drwx------ 56 sirko sirko 12288 Dec 31 12:37 ../ drwxrwxr-x 8 sirko sirko 4096 Dec 31 13:20 .git/ -rw-rw-r-- 1 sirko sirko 3243 Dec 31 13:20 id_rsa -rw-r--r-- 1 sirko sirko 748 Dec 31 12:41 id_rsa.pub -rw-rw-r-- 1 sirko sirko 64 Dec 31 13:20 my_document.txt

Apparently git filter-branch is applying this changes only to the current branch, which is actually not what I want. To make this work, it seems that I have to run git filter-branch in every existing branch, which makes it pretty annoying. After reading more in the (git docs)[https://git-scm.com/docs/git-filter-branch], I found that I need to apply the --all option.

(master) $ git filter-branch --tree-filter 'rm -f id_rsa' HEAD --all
Rewrite c69deb9779a30e6335ab1a8ac1a0825cfc9302e4 (7/7)
Ref 'refs/heads/master' was rewritten
WARNING: Ref 'refs/heads/master' is unchanged
Ref 'refs/remotes/origin/master' was rewritten
WARNING: Ref 'refs/remotes/origin/master' is unchanged
Ref 'refs/remotes/origin/new-feature' was rewritten
(master) $ git checkout new-feature
(new-feature) $ ll
total 44
drwxrwxr-x  3 sirko sirko  4096 Dec 31 13:41 ./
drwx------ 57 sirko sirko 12288 Dec 31 13:41 ../
drwxrwxr-x  8 sirko sirko  4096 Dec 31 13:41 .git/
-rw-rw-r--  1 sirko sirko   748 Dec 31 13:41 id_rsa.pub
-rw-rw-r--  1 sirko sirko    64 Dec 31 13:41 my_document.txt

That seems to be exactly what I want and in the end I just need to git push --all --force my changes. After doing this, all collaborators should dump their local versions and clone a fresh version from the origin.

Another alternative to working with git filter-branch is BFG which has some more nifty features.

This tool provides some commands to completely remove big files as well as passwords from your Git history. Sadly I could not get it properly working, big files are still persistent as a git object and passwords can not be deleted because they are protected by 'HEAD'. I could not really find a solution for these problems. Maybe you are more lucky!

The easiest and much simpler solution is to initialize a new git repository, after making sure to have all sensitive information removed. The downside is obviously the loss of the project's Git history.

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How to report a bug

The simplest way to contribute to an open source project is to file an issue. Here are a few steps for you to file issues that are useful for the project maintainers.

1. Make sure it hasn't been reported yet

A quick Google search should return one or more results about the issue. If it's user error, just change the way you are using the code and move on.

If that doesn't work, find the project (it's probably on Github) and search through open and closed issues. If it's filed and open, try to add more information to make it easier to solve. (Please please please don't just add another +1 to a series of +1s)

If you couldn't find any issues, submit an issue (Beware: some projects will encourage you to post to their mailing list before filing an issue)

2. Submit a useful issue report

Don't just post the title of the error and what you were doing when it happened.

Please be as specific as possible!

Post information about:

  • The environment (a snapshot of Gemfile.lock could help)
  • The error message (a good candidate for the issue's title)
  • The backtrace should always be included in the description
  • If there is some configuration involved, add it to the description

3. Bonus points

  • Try a couple of alternatives and see what results you get. Save all the output, which might be useful for the issue's resolution. I know that most of us try different solutions before filing an issue.

  • If you want to show the maintainer an example of the problem, you could create a sample application that generates the problem, using the same configuration and the same dependencies you have in your application.

  • If you found the problematic line in the library, you could enhance the tests to cover the scenario that you are seeing. The best libraries have near 100% code coverage, so adding another scenario could be easier than you think. You don't need to find the solution, but seeing a failing spec will definitely make it easier to find a solution.

4. Share your monkeypatch

Most of us will monkeypatch our application and move on. This sucks!

You should file the issue, so that other programmers will benefit from your "wasted" effort.

If you monkeypatched it in a horrible way, add it to the issue as well. The project maintainer or other programmers might find that it isn't such a horrible patch after all.

To sum things up

I've explained a couple of ways that you can make a contribution to an open source project. I started with the simpler steps and then I moved on to the more advanced contributions.

Ideally, detailed issue reports will become pull requests in the future. You (or someone else) might send the pull request, but it all begins with a detailed description of the problem you are seeing.

Don't just say "It doesn't work!", don't be that person! Next time file an issue so that we can all benefit from your pain.

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Adding Docker to a Ruby gem

As a maintainer of a few Ruby gems, I have to decide what is accepted and what gets rejected into the gems. The other day someone submitted a pull request to add a Dockerfile to DatabaseCleaner

I thought it was a good idea, because the current version of DatabaseCleaner requires you to have Postgres, MySQL, Redis, and Mongo up and running before you run rake.

Here are the steps:

  1. Download the Docker Toolbox, a 176+ MB package.

  2. Install the package, which will expand to 400+ MB in your filesystem.

  3. In the terminal: docker-machine start default

  4. Then within your project: docker-compose up (before this I had to run eval "$(docker-machine env default)" because of this issue). Get ready to wait for a few minutes while it sets up your virtual machine.

  5. Finally: docker-compose run --rm gem

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