I had the opportunity to review a client’s production Drupal installation recently. This is a new site and traffic is just starting to pick up. Drupal is a popular LAMP stack open source CMS system using the MySQL Database.

Unfortunately I don’t always have the chance to focus on one product when consulting, sometimes the time can be minutes to a few hours. Some observations from looking at Drupal.

Disk footprint

Presently, volume and content is of a low volume, but expecting to ramp up. I do however find 90% of disk volume in one table called ‘watchdog';

+--------------+--------------+--------------+-------------+--------+
| table_schema | total_mb     | data_mb      | index_mb    | tables |
+--------------+--------------+--------------+-------------+--------+
| xxxxx        | 812.95555878 | 745.34520721 | 67.61035156 |    191 |
+--------------+--------------+--------------+-------------+--------+

+-------------------------------------------+--------+------------+------------+----------------+--------------+--------------+-------------+
| table_name                                | engine | row_format | table_rows | avg_row_length | total_mb     | data_mb      | index_mb    |
+-------------------------------------------+--------+------------+------------+----------------+--------------+--------------+-------------+
| watchdog                                  | MyISAM | Dynamic    |      63058 |            210 | 636.42242813 | 607.72516251 | 28.69726563 |
| cache_menu                                | MyISAM | Dynamic    |        145 |         124892 |  25.33553696 |  25.32577133 |  0.00976563 |
| search_index                              | MyISAM | Dynamic    |     472087 |             36 |  23.40134048 |  16.30759048 |  7.09375000 |
| comments                                  | MyISAM | Dynamic    |      98272 |            208 |  21.83272934 |  19.58272934 |  2.25000000 |

Investigating the content of the ‘watchdog’ table shows detailed logging. Drilling down just on the key ‘type’ records shows the following.

mysql> select message,count(*) from watchdog where type='page not found' group by message order by 2 desc limit 10;
+--------------------------------------+----------+
| message                              | count(*) |
+--------------------------------------+----------+
| content/images/loadingAnimation.gif  |    17198 |
| see/images/loadingAnimation.gif      |     6659 |
| images/loadingAnimation.gif          |     6068 |
| node/images/loadingAnimation.gif     |     2774 |
| favicon.ico                          |     1772 |
| sites/all/modules/coppa/coppa.js     |      564 |
| users/images/loadingAnimation.gif    |      365 |
| syndicate/google-analytics.com/ga.js |      295 |
| content/img_pos_funny_lowsrc.gif     |      230 |
| content/google-analytics.com/ga.js   |      208 |
+--------------------------------------+----------+
10 rows in set (2.42 sec)

Some 25% of rows is just the reporting one missing file. Correcting this one file cuts down a pile of unnecessary logging.

Repeating Queries

Looking at just 1 random second of SQL logging shows 1200+ SELECT statements.
355 are SELECT changed FROM node

$ grep would_you_rather drupal.1second.log
              7 Query       SELECT changed FROM node WHERE type='would_you_rather' AND STATUS=1 ORDER BY created DESC LIMIT 1
              5 Query       SELECT changed FROM node WHERE type='would_you_rather' AND STATUS=1 ORDER BY created DESC LIMIT 1
              3 Query       SELECT field_image_textarea_value AS value FROM content_type_would_you_rather WHERE vid = 24303 LIMIT 0, 1
              4 Query       SELECT changed FROM node WHERE type='would_you_rather' AND STATUS=1 ORDER BY created DESC LIMIT 1
              6 Query       SELECT changed FROM node WHERE type='would_you_rather' AND STATUS=1 ORDER BY created DESC LIMIT 1
             10 Query       SELECT changed FROM node WHERE type='would_you_rather' AND STATUS=1 ORDER BY created DESC LIMIT 1
              9 Query       SELECT changed FROM node WHERE type='would_you_rather' AND STATUS=1 ORDER BY created DESC LIMIT 1
              8 Query       SELECT changed FROM node WHERE type='would_you_rather' AND STATUS=1 ORDER BY created DESC LIMIT 1
              9 Query       SELECT field_image_textarea_value AS value FROM content_type_would_you_rather WHERE vid = 24303 LIMIT 0, 1

There is plenty of information regarding monitoring the Slow Queries in MySQL, but I have also promoted that’s it not the slow queries that ultimately slow a system down, but the 1000’s of repeating fast queries.

MySQL of course has the Query Cache to assist, but this is a course grade solution, and a high volume read/write environment this is meaningless.

There is a clear need for either a application level caching, or a database redesign to pull rather then poll this information, however without more in depth review of Drupal I can not make any judgment calls.