mod_log_sql 2.0 Documentation

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Approach

This project was formerly known as "mod_log_mysql." It was renamed "mod_log_sql" in order to reflect the project goal of database in-specificity. The module currently supports MySQL, but support for other database back-ends is underway.

In order to save speed and overhead, links are kept alive in between queries. This module uses one dedicated SQL link per httpd child, opened by each child process when it is born. Among other things, this means that this module supports logging into only one MySQL server, and for now, also, only one SQL database. But that's a small tradeoff compared to the blinding speed of this module. Error reporting is robust throughout the module and will inform the administrator of database issues in the Apache ErrorLog for the server/virtual server.

Virtual hosts are supported in the same manner they are in the regular logging modules. The administrator defines some basic 'global' directives in the main server config, then defines more specific 'local' directives inside each VirtualHost stanza.

A robust "preserve" capability has now been implemented. This permits the module to preserve any failed INSERT commands to a local file on its machine. In any situation that the database is unavailable -- e.g. the network fails or the database host is rebooted -- mod_log_sql will note this in the error log and begin appending its log entries to the preserve file (which is created with the user and group ID of the running Apache process, e.g. "nobody/nobody" on many Linux installations). When database availability returns, mod_log_sql seamlessly resumes logging to it. When convenient for the sysadmin, he/she can easily import the preserve file into the database because it is simply a series of SQL insert statements.