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  File System vs Core Data: the image cache test

Code for this project is on GitHub While doing a full re-write of Droplr's iOS app for the 2.0 launch, I couldn't find any good file/image caches out there had a particular feature I really wanted: extending item expiration whenever it's touched. I set out to write my own — which wasn't that much of a challenge — but somewhere along the process I had this crazy idea that perhaps (SQLite-backed) Core Data would be a much better tool for the job: No mismatch between cache index ...

   File system.Image cache,Multimedia     2012-02-01 08:52:02

  Some Thoughts on Twitter's Availability Problems

As a regular user of Twitter I've felt the waves of frustration wash over me these past couple of weeks as the service has been hit by one outage after another. This led me to start pondering the problem space [especially as it relates to what I'm currently working on at work] and deduce that the service must have some serious architectural flaws which have nothing to do with the reason usually thrown about by non-technical pundits (i.e. Ruby on Rails is to blame). Some of my suspicions ...

   Twitter,Architecture,Availability,Design     2011-08-12 07:39:21

  Why We Moved Off The Cloud

Cloud computing is often positioned as a solution to scalability problems. In fact, it seems like almost every day I read a blog post about a company moving infrastructure to the cloud. At Mixpanel, we did the opposite. I’m writing this post to explain why and maybe even encourage some other startups to consider the alternative.First though, I wanted to write a short bit about the advantages of cloud servers since they are ideal for some use cases.Low initial costs. Specifically, you...

   Cloud,Cloud computing,Mixpanel,Get off,Disadvantage,Drawback     2011-10-28 10:22:32

  Find files by size in Linux

In Linux systems, you may encounter a situation where there is no enough space on the system while you are trying to install some new packages or writing some data. In this case, you may want to clear some unneeded files. A frequent need will be find the largest files in the system so that they can be deleted first and disk space can be released quickly. In this post, we will show a simple command to find files by size so that we know what files are taking the specified space on the system, This...

   LINUX,FILESIZE,FIND     2020-04-25 08:02:45

  Unknown system variable 'query_cache_size' in DbVisualizer while accessing MySQL

DbVisualizer is a very popular GUI application to view the data stored on a database. It supports various databases such as Oracle, MySQL etc. It relies on different database drivers to connect to the database server and access the data stored there.  In this post, we will try to solve one problem when accessing the latest MySQL database(8.0+) through DbVisualizer. MySQL database starting from 8.0 has lots of changes which may not be compatible with old version of software or libraries whic...

   MYSQL,MYSQL 8,DBVISUALIZER,QUERY_CACHE_SIZE     2018-06-30 03:48:17

  How to optimize MySQL insert statement

For a big data system, one problem is the data access efficiency, one more problem is that the data insertion is very slow. We had a service system, the data loading process would take 4-5 hours. This time consuming operation is risky since if the program is interrupted during the loading process, it might be rerun, this will be troublesome. So it's necessary to improve the insertion efficiency for big data systems. Here we provide two optimization suggestions. 1. Combine multiple insert stateme...

   MySQL,insert,optimization     2012-10-24 22:03:13

  Amazon is a good company but doesn't have the best business model

Public opinion about a company is usually based on its performance. If it performs well, people will praise it, otherwise people will blame it. In 1999, Apple was still a broken apple(Steve Jobs's talent and effort was paid off yet). Public opinion about Apple was the closed model caused Apple's failure. They built hardware themselves, developed software themselves and delivered service themselves, this is certainly not sustainable. But Steve Jobs let everyone see this new model. In order to con...

   Business model,Amazon,Apple, Microsoft     2013-07-02 11:34:45

  SQLite C/C++ function interfaces

Some simple introduction to the SQLite function interfaces. First let's check some error codes defined in SQLite3 (They are in SQLite3.h file in the SQLite installation).#define SQLITE_OK           0   /* Successful result */  /* beginning-of-error-codes */  #define SQLITE_ERROR        1   /* SQL error or missing database */  #define SQLITE_INTERNAL     2&nb...

   SQLite,Function interface,C/C++     2012-07-04 12:23:43

  Introducing LocalDB, an improved SQL Express

Updated 2011-11-28: Added reference to the walkthrough of using LocalDB in Visual Studio 2010 and to the new LocalDB Installer. Updated 2011-11-02: Added reference to .NET Framework 4 support for LocalDB in the Q&A section. Introduction It gives me great pleasure to introduce a new version of SQL Express called SQL Express LocalDB. LocalDB is created specifically for developers. It is very easy to install and requires no management, yet it offers the same T-SQL language, programming surfac...

   LocalDB,Microsoft,SQL Express     2012-03-31 00:13:43

  Cache Reheating - Not to be Ignored

An important aspect to keep in mind with databases is the cost of cache reheating after a server restart. Consider the following diagram which shows several cache servers (e.g., memcached) in front of a database server.This sort of setup is common and can work quite well when appropriate; it removes read load from the database and allows more RAM to be utilized for scaling (when the database doesn’t scale horizontally). But what happens if all the cache servers restart at the same time, s...

   Database,Cost,Cache reheating,Advice     2011-09-21 09:47:29

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