Monday, October 20, 2014

Another weekend project

It takes quite a lot of energy to finish watching the entire five seasons of Breaking Bad. To finish it strong, this weekend I decided to try something that I haven't done for almost 18 years.

Monday, September 01, 2014

Gitcon, runtime configuration via a Git repo

This weekend, aside from taking kid to football game and various classes, changing diapers and watching "Breaking bad", I've been working on an new small open source library, Gitcon, which allows Java application to decouple some configuration into a standalone source repository so that software owner can modify configuration without deploying application for every modification. It is a cheap approach to dynamic configuration.

By the way, I was very surprise to find out that the term "Gitcon" has not been reserved for "Git conference" so far.


What led me to this project was a set of requirements:
  1. As a start, the configuration means properties file
  2. As a start, only Git source repository needs to be supported
  3. As a start, it only needs to gets configuration for once when application starts. The configuration is used to populate Spring application context where beans are mostly singletons. Software owner needs to restart application to pick up configuration change.
  4. The library must be very friendly to Spring
  5. It gets file from Git repo authenticated via SSH key.
  6. The SSH private key must be configurable
  7.  This is outside the scope of the library, but the SSH key comes from S3, which is authenticated by instance profile
  8. When SSH key is not specified, default one in user's home directory is applied. This is for development purpose.
  9. One Spring context may includes multiple properties coming from multiple repositories authenticated with different SSH keys.
  10. One properties file can include another under the same repository
 These requirements are the minimal goals that the first version of Gitcon must achieve in order to replace configurations of some existing applications.


The design is fairly straightforward. All it needs is to cope with the limitations from Jsch that JGit relies on.

1. S3FileFactoryBean

S3FileFactoryBean is something that takes an IAM, a bucket and a key, downloads a file from S3 into local temporary directory, returns the file and deletes it when Spring context closes. Since the logic is generic to the purpose of Gitcon, it lives in a neutral package, kaufman-aws as artifact org.cyclopsgroup:kaufan-aws:0.0.2.

<bean id="gitSshKeyFile" class="">
    <constructor-arg value="my-s3-bucket" />
    <constructor-arg value="my-app/git-ssh-private.key" />

2. Clone, checkout Git repo with JGit

The easiest way to clone a Git repo is to use JGitLocalResourceRepository. With support from Eclipse JGit, this class defines Git repository URI, the access to Git repository and optionally the path to SSH private key. You may find out more details in Javadoc. An example:

<bean id="gitResourceRepo"
        value="" />
    <property name="sshIdentityFile" ref="gitSshKeyFile" />

3. Create properties

The class GitconPropertiesFactoryBean simply creates Properties instance out of given ResourceRepository and a path to properties file. Since it creates Properties with ExtendedProperties, variable replacement and file inclusion is supported.

<bean id="appProperties"
    <constructor-arg ref="gitResourceRepo" />
    <constructor-arg value="myapp/" />

If you haven't tried, ExtendedProperties interprets properties file in a different way than Properties and exposes the content with a much more user friendly API. It is an ancient class from commons-collections, if a human is as old as this class, he would probably get a driver license by now.

4. Expand properties in Spring

This is done by a simple setup in Spring. It doesn't belong to Gitcon but I put it here so that the story is complete. The following config does the work.

<context:property-placeholder properties-ref="appProperties" />

To learn more

Like other CyclopsGroup projects, Gitcon Maven site is published to Very soon I will come up with a few wiki pages with official guides and examples.

Javadoc can be found here. Source code is in Github. The first version, org.cyclopsgroup:gitcon:0.0.1 has been published into Maven central repository.

If you have question, please feel free to contact me in Github, Facebook or Google+. Thank you for reading.

Sunday, March 09, 2014

The longest week

A week ago I came out from a surgery room in Memorial hospital in South Bend and had one of my most painful moments in life. In the following week, pain pill and IV were my friends. Now after a week of recovery, I finally got back to my sanity and sit in front of my computer.

Feb 25th noon, I fell down on an icy drive way on my way to the car. It wasn't a light fall. When it happened I heard a sharp pop and saw my right foot bent up. This is something I have only seen on YouTube. Fortunately my wife was with me, it could be a whole lot worse without her. At the very second I fall on the ground many things passed my mind. My pregnant wife, my daughter whom I read story to, my travel plan in next month, my job in Chicago, and the fact that my son will grow up with a cripple daddy who probably can't hold him. Then came the pain, which confirmed what happened is real.

For the second time in life, an ambulance took me to hospital. A nurse looked at CT scan in hospital and said, "how could you fall to break leg like this". It is a good question, I ask myself this question all the time.

The bed in hospital is a really good bed. Softness is controlled electrically, and buttons are everywhere to adjust position in all imaginable ways. If I were 10 years younger I would be curious, playing with the bed and discovering all hidden features. But in reality, all I worried is how does mommy explain to Yilin daddy's absence.

Finally Yilin came and visited me at night. My girl was a little scared. She saw my leg and covered eyes with hands. However it didn't take long before she warmed up, climbed up and down the room and made funny face to nurses. Before leaving she asked me, "Daddy why can you still talk?", then she skipped away.

The surgery occurred on the next day. Tibia was broken into 3 pieces and Fibula into 2. The orthopedic doctor decided to insert a titanium rod into the broken bone and fix it with nails on both ends. I didn't see how it was done on surgery table, but it sounded to me that the surgery is a walk in the park for the doctor. It went well and then it was just the matter of long, painful recovery process -- swelling, bone recovery, and celebration party.

There's so much that I wanted to do,  articles to read, work to catch up, movies to watch. I'm always lack of time but in hospital, finally I had enough time, enough resource but I couldn't do any of them. Trapped in a narrow space hour after hour, with pain and insomnia day after day, my mindset changed into a state where brain is frozen and eyes are wide open. Not being able to do anything meaningful for long time becomes the biggest torture for me, which is way much worse than the pain itself.

However don't worry my friends. In the beginning of this blog I mentioned I got back to sanity finally. Right now, things are getting better everyday. I moved from hospital to a sofa in home, then started walking with a pair a crutches once a while. The bruise looks different every morning. I had hard time sleeping, but day time becomes enjoyable. Now I'm sitting in a wheelchair, which Yilin is super excited about.

As I started reading news I realized I just missed a very turbulent week. The Ukraine crisis, terrorism in Kunming and missing Malaysia airplaine, all happened in the same week. Lives are lost and many need help much more than I do. I hope they get better every day as well.