《小强升职记》相关电子表格下载GTD Life | 19 Mar 2009

22:40 Product: Redis - Not Just Another Key-Value Store » High Scalability - Building bigger, faster, more reliable websites.

With the introduction of Redis your options in the key-value space just grew and your choice of which to pick just got a lot harder. But when you think about it, that's not a bad position to be in at all.

Redis (REmote DIctionary Server) - a key-value database. It's similar to memcached but the dataset is not volatile, and values can be strings, exactly like in memcached, but also lists and sets with atomic operations to push/pop elements.

The key points are: open source; speed (benchmarked performing 110,000 SET operations, and 81,000 GETs, per second); persistence, but in an asynchronous way taking everything in memory; support for higher level data structures and atomic operations.

The home page is well organized so I'll spare the excessive-copying-to-make-this-post-longer. For a good overview of Redis take a look at Antonio Cangiano's article: Introducing Redis: a fast key-value database.

If you are looking at a way to understand how Redis is different than something like Tokyo Cabinet/Tyrant, Ezra Zygmuntowicz has done a good job explaining their different niches:

I feel like I’ve been seeing this a lot lately.

occasionally, seemingly innocuous selects take unacceptably long.

Or

Over the past few weeks, we’ve been having bizarre outages during which everything seems to grind to a halt… and then fixes itself within 5 minutes. We’ve got plenty of memory, we’re not running into swap, and we can’t find any queries that would seem to trigger outages: just tons of simple session requests all hung up for no obvious reason.

Problems like this are always hard to debug. If it happens twice a week for 5 minutes at a time, your chance of getting someone logged onto the machine to watch it in action are pretty slim. And of course, when they do look at it, they see nothing wrong on the surface; it takes some very clever, very fast work with OS-level debugging and tracing utilities to really prove what’s happening.

The two cases mentioned above were caused by scalability/concurrency/locking problems in the query cache. (One was on Windows, and we fixed it by guessing. The other was on GNU/Linux and Maciek isolated it with his elite skillz.) So if you’re having random lockups, you might try disabling the query cache, and see if that solves it.

Hopefully this blog post will show up on Google and save someone time and money!

Entry posted by Baron Schwartz | No comment

Add to: | | | |