Tuesday, March 10, 2015

Facebook: All time ranges must be midnights - Not every day is like another, some days are 23h and some are 25h long

Facebook has funny thing about their API. They require timestamps used in their report to be on midnight boundary in your local timezone.

Originally I wrote this code:

facebook_time = DateTime.parse(@run_date.to_s).utc.in_time_zone('America/Los_Angeles').midnight.to_i
time_interval="{time_start:#{facebook_time}, time_stop:#{facebook_time+24*3600}}"

That worked great until daylight savings kicked in, and failed with "All time ranges must be midnights", so after a bit of debugging I changed it to this one:

facebook_time = DateTime.parse(@run_date.to_s).utc.in_time_zone('US/Pacific-New').midnight.to_i
facebook_time_end = DateTime.parse((@run_date+1).to_s).utc.in_time_zone('US/Pacific-New').midnight.to_i
time_interval="{time_start:#{facebook_time}, time_stop:#{facebook_time_end}}"
I hope this will help someone spend less time debugging.

Friday, February 20, 2015

Creating Users and Databases

It is tedious to create database. Well, not really hard, just annoying.

While 3 lines of code to create database, create user and grant user privileges to the database are not hard to write, one needs to remember correct syntax and to place same text 2-3 times.

To mitigate this issue, I created a tiny template to help me with it. It is available at:

Or embedded here for your convenience:

Sunday, January 4, 2015

Did you ever wanted to know when a webpage changed?

There is a new web service - WebFollower - what it does is a simple simple, but still important task.
Here is how it works - you sign-up with your Facebook account and go to the dashboard.
On the dashboard you add URLs you'd like to monitor and web follower crawler checks if page has changed. If it didn't than nothing happens and WebFollower's crawler checks it again later. If it did change WebFollower sends you an email notifying you that page changed. If you want to be notified of change when page changes again, you'll need to re-enable it on the dashboard.

That's it - a simple and hopefully useful service.

Monday, August 25, 2014

Setting up ghost on the Openshift

In past few days I decided that I would like to keep track on my progress in how I learn new stuff. After some consideration I hope a good way to organize my work would be to use Ghost: is just a blogging platform funded on Kickstarter last year. I have heard all the hype when Ghost got funded and tried to use it early on, but it was disaster to when it was first released. Also, I didn't have a good use case to keep working at it, but now... here is an opportunity.

Quick googling ghost resulted in number of links as a community seem to be sprouting around it. I read a good introduction on setting it up and on its current features on "Ghost for Beginners". The site covers how to set Ghost on Ghost(PRO), AWS and DigitalOcean, but there was nothing about my favorite hosting solution - OpenShift. So I figured I can write a post on setting Ghost on OpenShift.

At first I tried to set it up using OpenShift's console, but that yielded in an error:

Attempting to install through web interface failed twice, I was a bit discouraged, so finally I attempted to try running rhc command from terminal. That worked like a charm:

rhc app create ghost nodejs-0.10 --env NODE_ENV=production --from-code https://github.com/openshift-quickstart/openshift-ghost-quickstart.git

And here is terminal output:

Application Options
Domain:                _MY_DOMAIN_
Cartridges:            nodejs-0.10
Source Code:           https://github.com/openshift-quickstart/openshift-ghost-quickstart.git
Gear Size:             default
Scaling:               no
Environment Variables: NODE_ENV=production

Creating application 'ghost' ... done

Waiting for your DNS name to be available ... done

Cloning into 'ghost'...
The authenticity of host 'ghost-_MY_DOMAIN_.rhcloud.com (' can't be established.
RSA key fingerprint is cf:ee:77:cb:0e:fc:02:d7:72:7e:ae:80:c0:90:88:a7.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'ghost-_MYDOMAIN_.rhcloud.com,' (RSA) to the list of known hosts.

Your application 'ghost' is now available.

  URL:        http://ghost-_MY_DOMAIN_.rhcloud.com/
  SSH to:     53fba91d5004466ac7000306@ghost-_MY_DOMAIN_.rhcloud.com
  Git remote: ssh://53fba91d5004466ac7000306@ghost-_MY_DOMAIN_.rhcloud.com/~/git/ghost.git/
  Cloned to:  /Users/_MY_USER_/Source/ghost

Run 'rhc show-app ghost' for more details about your app.

Ghost correctly appears in the console after that:

Here is a snapshot of Ghost homepage:

I added the user, and published test post:

Adding a custom domain name boils down to:
    1. add an alias using RHC
       rhc alias add ghost MY_CUSTOM_NAME.MY_DOMAIN.COM
    2. setting up DNS alias:
       from: MY_CUSTOM_NAME 
       to: ghost-_MY_DOMAIN_.rhcloud.com
       as: CNAME (alias)
    3. setting up DNS name in config.js:
       edit config.js and replace:
         url: 'http://'+process.env.OPENSHIFT_APP_DNS,
         url: 'http://_MY_CUSTOM_NAME.MY_DOMAIN.COM/'

I use namecheap.com and have had a great experience with them for a couple of years now. They have very easy to use admin panel (not the most intuitive, but very efficient).

Adding google analytics to the blog:
  go to your RHC folder with the application
  edit file: content/themes/YOUR_THEME/default.hbs
  just before end < /head> tag insert your GA code.
  git commit -a # to commit to code repository
  git push # to push to OpenShift

I will update this post with other steps I plan to undertake, staring from ensuring that there is a scheduled backup, over adding google analytics and google adsense to the blog.

Thursday, May 22, 2014

FIX: Django, uwsgi, Apache, ProxyPass, host is localhost and using ProxyPreserveHost

I just spent some time trying to figure out how to set our Django application.

Our setup is:
  Apache (handles HTTPS and client certificates) is front-end proxy to uwsgi
  uwsgi is used to run Django application in the backend.

The problem we faced is that our redirects were broken as links build by django used 'localhost' instead of name of the virtual host. After looking through solutions, and finding some of the issues like:

I looked into django handling of get_host() and tried to understand what's happening.
Long story short, Apache passed HOST header as 'localhost', this led to search of apache documentation, as I was thinking that I reset headers using 
   RequestHeader set X-FORWARDED-PROTOCOL ssl
   RequestHeader set X-FORWARDED-SSL on
   RequestHeader set X-FORWARDED-HOST *hostname*
   RequestHeader set HTTP_HOST *hostname*
   RequestHeader set HOST *hostname*
but apparently, apache does not pass these through the proxy... so... drumroll, saving grace is:
and side note, ProxyPreserveHost needs to be on the VirtualHost level or higher.

I hope this short post will save you some time :)

Tuesday, March 11, 2014

MacOSX & Chrome: How to make scrollbars ALWAYS visible in your web application

If you are, like me, annoyed that overflow: scroll does not display scrollbars on all MacOSX computers in chrome; you can actually force Chrome to behave by just adding this to your CSS:

::-webkit-scrollbar {
    -webkit-appearance: none;
    width: 7px;
::-webkit-scrollbar-thumb {
    border-radius: 4px;
    background-color: rgba(192,192,192,.3);
    -webkit-box-shadow: 0 0 1px rgba(255,255,255,.5);

Friday, February 28, 2014

How to calculate MD5 and SHA1 fingerprints using web browser?

Downloads and fingerprints

MD5 and SHA1 fingerprints often listed next to the large files one can downloads from files are there to ensure that data downloaded is the same as the data on the server. It is a good policy to always check if downloaded file has the same fingerprint as the one provided from the trusted source.

How to perform MD5 or SHA1 check using web browser?

While you can download the command line tools (shasum and md5sum) or use GUI tools to calculate MD5 and SHA1 checksum, it seems that today's browsers should be suited to let you do that calculation without resorting to specialized applications. One such tools that does not require you to download software, but lets you check MD5 and SHA1 sums right from the browser is Checksum MD5 and SHA1 calculator. This handy tool let you pick one or more files, and without uploading them anywhere check them right from the comfort of your device. It works with most of the modern browsers (IE10+, Chrome, Firefox, Safari) and it even works with your mobile devices if you ever need to do that sort of calculation (for example for .apk you just downloaded).