» 2005 » June

http://grokker.com/

A web based version of Grokker is now available for free.

I use Grokker for ideas and to find interesting links between sites that I am working on sites that I like.

I wonder what the business model behind this will be?

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http://www.scottmccloud.com/comics/icst/icst-6/icst-6-full.html

The idea of making a small amount of money from a large amount of people has always interested. Lately I have been thinking about the concept of donationware. In the course of my normal coding projects, I’m always coming up with mini-apps that would be great to release to the rest of the world. Maybe micropayments is the way to go.

Popularity: 7%

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Every month or two I take a project to increase the performance of a web application and/or server setup. Most of these can be easily reworked by adding a few simple (or compound) indices on key tables.

I am increasingly adding more and more clients who require a multi-server setup to handle their server load. The easiest setup is a single database server behind a couple of fast web only servers (more in depth on that in a later post). These setups sometimes require tweaking every last bit of performance out of the database server to prevent the jump to a multi-database server setup.

Notes from today:

• Opened_tables: Number of tables opened since this server process started. If the value is large, increase table_cache. Typically you would want this to be less than 1 or 2 opened tables per second.
• Qcache_hits: This statistic shows the number of accesses to the new MySQL query cache. The query cache stores the results of frequently-used queries so as to speed up response time; a high value here means that MySQL is working efficiently by using the cache instead of rebuilding result sets every time the same query is fired.
• Select_full_join: Joins performed without indexes. This should be zero. Easiest performance issue to fix, caused by development errors.
• Select_scan: Number of queries that performed a full table scan. In some cases these are OK but their ratio to all queries should be constant. if you have the value growing it can be a problem with the optimizer, lack of indexes or some other problem.
• Slow_queries: Number of queries longer than –long-query-time or that are not using indexes. These should be a small fraction of all queries. If it grows, the system will have performance problems.
• Threads_created: This should be low. Higher values may mean that you need to increase the value of thread_cache or you have the amount of connections increasing, which also indicates a potential problem.

Other Commands:

• tail -f /var/log/mysql-slow.log

  take each slow query and run an

  EXPLAIN [query]

  in a query window to see what indexes are being used

• mysql SHOW FULL PROCESSLIST;
• http://jeremy.zawodny.com/mysql/mytop/
• vmstat 1
• mysqldumpslow [slow-query-logfile]

  command to get a summary of the queries that appear in the log.

• mysqladmin extended -i10 -p
• mysqladmin extended -i10 -p | grep Threads_cached
• SELECT @@global.[any-system-variables];

  (ie.

  SELECT @@global.thread_cache_size;

  )

Links for more info

• http://dev.mysql.com/doc/mysql/en/query-cache-configuration.html
• http://dev.mysql.com/books/hpmysql-excerpts/ch06.html

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Has anyone had the problem with Apache dying after being up over a week with the following message?

There is a moderate amount of discussion on it, but no solutions I found. Memory leaks.

The temporary solution to clear up the semaphores for Apache with a:

works but, it only treats the symptom (dead Apache) not the cause. SIM and cleaning the semaphores daily is the best I have found.

Popularity: 9%

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