Resume and bio of the author Couple of articles related to my hobby - robotics
My impressions about immigration to Australia. In Russian only. Recipes for everyday problems solving
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Software-related posts A lot of info about hardware
Different tools you might find useful Posts about various web technologies
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Andrey Mikhalchuk’s Blog

Technoblog about life

Nov 15, 2013 How to make browser offline cache retrieve new version of the page when browser is online, but keep using cache when it is offline

Offline cache is awesome! For certain things. For most regular web pages it is unfortunately not. Here is web developer’s most frequent use for the offline cache: make browser use cached version of the page when browser is offline but refresh it when it gets online. What could be simpler and more natural purpose for the OC? Well, unfortunately it wasn’t designed to work like this out of the box. Even when your browser goes online it will keep using the cached version “indefinitely” until the cache manifest is updated. So what do we do in this situation?

Nov 12, 2013 AWS EC2 ssh not responding in RHEL 6.4 AMI

I was fighting with an AWS bug today seeming just ridiculous for a system that makes ssh the only way to access the server. With no console login EC2 users are completely dependent on flawless sshd operation and Amazon team just did a really bad job preparing the RHEL 6.4 image.
So here are the symptoms: you create an image from a perfectly working system with the purpose to clone it. Then you create new instance from the AMI and it seems working fine too, you can ssh to it no problem. After a reboot or too it suddenly stops responding to ssh thought the rest of the system seems working fine (HTTP server for instance). Server logs do not show any errors. Reboots do not help and EC2 doesn’t provide console access to the server.
Here is the solution:

Nov 8, 2013 How to use large / multiline text as a field in mongodb

I’m working on a project that requires storing large multiline chunks of text in MongoDB. The chunks should be inserted in the database during initial database population, so I need to enter them somewhere in db population script. Unfortunately you can’t just put something like this:

db.tests.insert( {
name: 'test',
text: 'this is
my superawesome
multiline content'
} )

Javascript/JSON do not support multiline text like this. Fortunately there are several options that made my life easier. Here they are:

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