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Showing entries 1 to 17

Displaying posts with tag: Caching (reset)

Tech Messages | 2013-03-10
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A special extended edition of Tech Messages for 2013-03-07 through 2013-03-10:

Some sharding support and cache locality optimization support for PHP MySQL driver
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It is time for christmas presents: some sharding support and cache locality optimizations are coming with PECL/mysqlnd_ms 1.5. PECL/mysqlnd_ms is a plugin for the mysqlnd library. The plugin adds replication and load balancing support to any PHP MySQL API (mysql, mysqli, PDO_MySQL) if compiled to use the mysqlnd library.

As a MySQL user you can choose between a wide variety of clustering solutions to scale-out. Your options range from eventual consistent solutions to strong consistent ones, from built-in (MySQL Replication, MySQL Cluster) to third party or home-grown. PECL/mysqlnd_ms is a client side load

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5 Tips to Cache Websites and Boost Speed
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Read the original article at 5 Tips to Cache Websites and Boost Speed

Often when we think about speeding up and scaling, we focus on the application layer itself.  We look at the webserver tier, and database tier, and optimize the most resource intensive pages.

There's much more we can do to speed things up, if we only turn over the right stones.  Whether you're using WordPress or not, many of these principals can be applied.  However we'll use WordPress as our test case.

Test Your Website speed

There are web-based speed testing tools that will help with this

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It’s about Time.
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WHAT TIME IS IT?

This post started with a simple question: “Does the function NOW() get executed every time a row is examined?” According to the manual,  “Functions that return the current date or time each are evaluated only once per query …. multiple references to a function such as NOW() … produce the same result. …. (However,) as of MySQL 5.0.12, SYSDATE() returns the time (the row is) executes. “

  • CURDATE() returns the current date.
  • CURTIME() returns the current time.
  • UTC_DATE() returns the current UTC date.
  • UTC_TIME() returns the current UTC time.
  • NOW() return the current date and time.
  • UTC_TIMESTAMP() returns the current UTC date and time.
  • SYSDATE() returns the
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Database Architectures & Performance
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For decades the debate between shared-disk and shared-nothing databases has raged. The shared-disk camp points to the laundry list of functional benefits such as improved data consistency, high-availability, scalability and elimination of partitioning/replication/promotion. The shared-nothing camp shoots back with superior performance and reduced costs. Both sides have a point.

First, let’s look at the performance issue. RAM (average access time of 200 nanoseconds) is considerably faster than disk (average access time of 12,000,000 nanoseconds). Let me put this 200:12,000,000 ratio into perspective. A task that takes a single minute in RAM would take 41 days in disk. So why do I bring this up?

Shared-Nothing: Since the shared-nothing database has sole ownership of its data—it doesn’t share the data with other nodes—it can operate in the



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Advanced Squid Caching in Scribd: Cache Invalidation Techniques
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Having a reverse-proxy web cache as one of the major infrastructure elements brings many benefits for large web applications: it reduces your application servers load, reduces average response times on your site, etc. But there is one problem every developer experiences when works with such a cache – cached content invalidation.

It is a complex problem that usually consists of two smaller ones: individual cache elements invalidation (you need to keep an eye on your data changes and invalidate cached pages when related data changes) and full cache purges (sometimes your site layout or page templates change and you need to purge all the cached pages to make sure users will get new visual elements of layout changes). In this post I’d like to look at

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Introduction to memcached
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These are the slides to a talk I did earlier this week for students of the professional bachelor in ICT course at KaHo St. Lieven. I wanted to give a clear and simple introduction to the memcached service, as I think it’s an invaluable tool in today’s web development.

10x Performance Improvements in MySQL – A Case Study
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The slides for my presentation at FOSDEM 2010 are now available online at slideshare. In this presentation I describe a successful client implementation with the result of 10x performance improvements. My presentation covers monitoring, reviewing and analyzing SQL, the art of indexes, improving SQL, storage engines and caching.

The end result was a page load improvement from 700+ms load time to a a consistent 60ms.

10x Performance Improvements – A Case Study View more presentations from Ronald Bradford.
Using the Query Cache effectively
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Maximize your strengths, minimize your weaknesses.

You can apply this approach to many things in life, I apply it to describing and using MySQL the product, and it’s components. The Query Cache like many features in MySQL, and indeed features in many different RDBMS products (don’t get me started on Oracle *features*) have relative benefits. In one context it can be seen as ineffective, or even detrimental to your performance, however it’s course grain nature makes it both trivial to disable dynamically (SET GLOBAL query_cache_size=0;), and also easy to get basic statistics on current performance (SHOW GLOBAL STATUS LIKE ‘QCache%’;) to determine effectiveness and action appropriately.

The Query Cache is course grained, that is it is rather simple/dumb in nature. When you understand the path of execution of a query

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Advanced Squid Caching in Scribd: Logged In Users and Complex URLs Handling
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It’s been a while since I’ve posted my first post about the way we do document pages caching in Scribd and this approach has definitely proven to be really effective since then. In the second post of this series I’d like to explain how we handle our complex document URLs and logged in users in the caching architecture.

First of all, let’s take a look at a typical Scribd’s document URL: http://www.scribd.com/doc/1/Improved-Statistical-Test.

As we can see, it consists of a document-specific part (/doc/1) and a non-unique human-readable slug part (/Improved-Statistical-Test). When a user comes to the site with a wrong slug in the document URL, we need

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Database Sharding at Netlog, with MySQL and PHP
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This article accompanies the slides from a presentation on database sharding. Sharding is a technique used for horizontal scaling of databases we are using at Netlog. If you’re interested in high performance, scalability, MySQL, php, caching, partitioning, Sphinx, federation or Netlog, read on …

This presentation was given at the second day of FOSDEM 2009 in Brussels. FOSDEM is an annual conference on open source software with about 5000 hackers. I was invited by Kris Buytaert and Lenz Grimmer to give a talk in the MySQL Dev

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Caching and Actually Speeding Things Up
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Image by Peter Forret via Flickr

I've ran into many people throughout my career that were under the impression that caching is a cure for cancer, world hunger and global warming. I myself often fall pray to the "just add more memory" approach for solving problems.
Some 5 years ago, while I was working with ASP classic and VB 6 (yes, you are allowed to chuckle now) on my online movie collection, I came up with the idea that nothing actually beats a flat and pre-processed HTML file for speed. I mean, this may seem obvious and no matter how many times I tried to add cache and do all sorts of tricks, nothing would beat a static file. The problem here is that
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Advanced Squid Caching for Rails Applications: Preface
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Since the day one when I joined Scribd, I was thinking about the fact that 90+% of our traffic is going to the document view pages, which is a single action in our documents controller. I was wondering how could we improve this action responsiveness and make our users happier.

Few times I was creating a git branches and hacking this action trying to implement some sort of page-level caching to make things faster. But all the time results weren’t as good as I’d like them to be. So, branches were sitting there and waiting for a better idea.

Few months ago my good friend has joined Scribd and we’ve started thinking on this problem together. As the result of our brainstorming we’ve managed to figure out what were the problems

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Caching and TTL behavior
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So, I am working on MemProxy some.  Mainly, I am trying to implement more of the Cache-Control header's many options.  The one that has me a bit perplexed s-maxage.  Particularly when combined with max-age.

s-maxage is the maximum time in seconds an item should remain in a shared cache.  So, if s-maxage is set by the application server, my proxy should keep it for that amount of time at the most.  Up until now, I have just been looking at max-age.  But, s-maxage is the proper one for a proxy to use if it is present.  I do not send the s-maxage through because this is a reverse proxy and, IMO, that is proper behavior for an application accelerating proxy.  However, I do send forward the max-age value that is set by the application servers.  If no max-age is set, I send a default as defined in the script.  Also, if

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Kickfire: stream-processing SQL queries
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Some of you have noticed Kickfire, a new sponsor at this year’s MySQL Conference and Expo. Like Keith Murphy, I have been involved with them for a while now. This article explains the basics of how their technology is different from the current state of the art in complex queries on large amounts of data.

Kickfire is developing a MySQL appliance that combines a pluggable storage engine (for MySQL 5.1) with a new kind of chip. On the surface, the storage engine is not that revolutionary: it is a column-store engine with data compression and some other techniques to reduce disk I/O, which is kind of par for the course in data warehousing today. The chip is the really exciting part of the technology.

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Dog-pile Effect and How to Avoid it with Ruby on Rails memcache-client Patch
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We were using memcache in our application for a long time and it helped a lot to reduce DB servers load on some huge queries. But there was a problem (sometimes called a “dog-pile effect”) - when some cached value was expired and we had a huge traffic, sometimes too many threads in our application were trying to calculate new value to cache it.

For example, if you have some simple but really bad query like

SELECT COUNT(*) FROM some_table WHERE some_flag = X

which could be really slow on a huge tables, and your cache expires, then ALL your clients calling a page with this counter will end up waiting for this counter to be updated. Sometimes there could be tens or even hundreds of such a queries

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Memcached: How do you install memcached? (CentOS 64 bit, Linux, Redhat, Fedora)
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Memcached is a very popular open source object caching server. It was developed to speed up livejournal.com by Danga Interactive.  We use memcached for a lot of our sites.  We use it for different purposes but one main purpose is to cache query results so we don’t have to keep hitting database.  As most [...]   [Read more...]
Showing entries 1 to 17

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