lunatechian (lunatech-ian)

one relating to, belonging to, or resembling lunatech

build your own base debian docker image

This is for somewhat paranoid people. I am not a fan of grabbing docker images from docker hub, especially for base OS images. I would rather build my own images, the process is not too complex. Below is the quick way to get a base debian os container build:
sudo apt-get install debootstrap
sudo debootstrap jessie jessie/
sudo sh  -c "cd jessie/ && tar cf ../jessie.tar ."
sudo sh -c "docker import - debootstrap/jessie < jessie.tar"
Now you can check if you have the images:
$ sudo docker images

REPOSITORY              TAG                 IMAGE ID            CREATED             SIZE
debootstrap/jessie      latest              814d88e17a23        15 minutes ago      274MB

$ sudo docker run -i -t debootstrap/jessie /bin/bash
root@92d078f4f147:/# lsblk ^C

Faster setup of virtualenv with devpi

Setting up the virtualenv can take a significant amount of time because it pulls down packages from PyPI. I was surprised that it does not try to use the locally installed packages. One way to speed up the rebuild is to use a local caching mirror of PyPI. This can be accomplished by using devpi.

Step 1: Install devpi package

sudo pip install devpi

Step 2: Add the following lines in your /root/.pip/pip.conf file

index-url  = http://localhost:3141/root/pypi/+simple/
extra-index-url  =

From now on, pip will first try to get the package from devpi-server running on your localhost first and if you do not have devpi-server running, will fallback to .

Step 3: Start the devpi-server on your localhost: devpi-server. Try installing a few packages or build a virtualenv. The command devpi-server -start will start the server and put it in background.

TODO - figure out how to start this from init.

They’re our servants, tools

"You can see that our real problem is another thing entirely. The machines only do figuring for us in a few minutes that eventually we could do for our own selves. They’re our servants, tools. Not some sort of gods in a temple which we go and pray to. Not oracles who can see into the future for us. They don’t see into the future. They only make statistical predictions—not prophecies. There’s a big difference there, but Reinhart doesn’t understand it. Reinhart and his kind have made such things as the SRB machines into gods. But I have no gods. At least, not any I can see."

The Variable Man, by Philip K. Dick

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Caching is not a silver bullet

Let us take a this hypothetical situation. You have to serve a web page. You want the whole page to be sent back in 500 ms (milliseconds). If your user has a good network and he is not too far from your webserver, you can further assume that around 50 ms will be spent on the network. This means that you have 450 ms to collect all the data about this web request, do the fancy manipulations (sorting/filtering/updating files etc.) and serve it to the user. You need to make four external calls to get this data - 2 of them to an external web service and 2 of them to your own database.

Now assume that one of your external webservice calls take one second to send back the result 50% of the time and one of your database queries can take upto a second to give back the result 25% of the time. What will you do to make sure none of your users ever have to wait for more than 500 ms to get back the page? (500 ms excludes the time taken to download the images/css/do fancy javascript magic).

Read more on my website

GPL still matters

Today morning I came across this piece of writing - Does GPL still matter?. The whole article is based on a few anecdotes from CEOs and marketing droids. They have gotten quite a few points wrong in the article.

GPL is a developer friendly license. The basic premise of the GPL is that the user should not subtract from the freedom he gets when redistributing software. GPL is not restrictive. It merely insists that whoever takes from the common pool must contribute back to the pool.

I would like to point to these 2 articles in support of GPL -

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interesting meetup on July 14

I attended the Hackers and Founders meetup yesterday. It was a high energy meetup and I liked it. When I walked in, I was already 2 hours late but there were still quite a few people around. I walked in, took a name tag and tried to "merge in". Merging was easy - the folks were friendly and did not mind if you joined the discussion.

Some observations

  • I did not have a good answer for "what are you working on right now" :-) . This made me realize that from a technology perspective, I have not worked on anything interesting for some time now. I have tinkered with a few things in the past 6 months (man!), but have not really done a deep dive on any of them.
  • There was a focus on programming language in the group. I am not sure if the choice of a programming language is really a big deal when creating a webapp. Rails, PHP, Python, Perl, Java - all have a good web framework. One of the arguments was that it would be difficult to organize PHP code in a coherent manner. In my opinion, that is a matter of discipline instead of language.
  • I did not find people thinking of totally different ideas. Or maybe, the folks were not telling those ideas :-) . The ideas floated around ads, community, social networking, websites etc.
  • I am not a unique case when it comes to the case of creating a startup. A few folks there had a regular job and were planning on side projects.
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