Log Files Oracle Application Server Tips by Burleson Consulting

The next section of the httpd.conf file defines log locations, logging levels, and formats.  Logging levels determine how much information is logged. The greater the level, the more information and the logs grow faster.

HostnameLookups Off

ErrorLog /home/oracle/oraportal904/Apache/Apache/logs/error_log

LogLevel warn

You can have OHS log the host name instead of the IP address, but that is not recommended since OHS must hit the DNS to resolve the IP address.  The default is HostnameLookups Off , which logs the IP address instead of the host name.  The ErrorLog directive establishes where the error log is located and the LogLevel determines how much information is logged.  The levels of logging in descending order of verbosity are:

Level
Description
Example
emerg
Emergencies - system is unusable.
"Child cannot open lock file. Exiting"
alert
Action must be taken immediately.
"getpwuid: couldn't determine user ?"
crit
Critical Conditions.
"socket: Failed to get a socket, exiting child"
error
Error conditions.
"Premature end of script headers"
warn
Warning conditions.
"child process 1234 did not exit "
notice
Normal but significant condition.
"httpd: caught SIGBUS, attempting to ??
info
Informational.
"Server seems busy?
debug
Debug-level messages
"Opening config file ..."

The selected level will log those items and all items above the selected level. 

Another important log is the access_log file.  OHS uses the module mod_log_config to log each request in the access_log file, normally located in ServerRoot/logs/access_log. 

The first step is to define one or more LogFormats.  The LogFormat directive can take one or two arguments.  If there is only one argument (the formatting variables), then it will be used in all subsequent TransferLog directives.  If there are two arguments (the formatting variables and an alias), then subsequent TransferLog and CustomLog directives can use the alias to define the format to use. 

In the httpd.conf file, Oracle has defined four formats with the LogFormat directive aliased by: combined, common, referrer, and agent. Next, the CustomLog directive is used to assign the ?common? format to the access_log file. 

LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
LogFormat "%h %l %u %t \"%r\" %>s %b" common
LogFormat "%{Referer}i -> %U" referrer
LogFormat "%{User-agent}i" agent
CustomLog /home/oracle/oraportal904/Apache/Apache/logs/access_log common

The CustomLog directive establishes the log location and format.  In the example above, CustomLog defines the location of the access_log file, and that it will use the format aliased by ?custom?.  It could also directly define the format rather than use the format alias. 

TransferLog functions like CustomLog, except that TransferLog takes the format of the last defined LogFormat without an alias, or if no LogFormat exists without an alias, it uses the Common Log Format (the default format).  We will see an example of TransferLog in the Virtual Host section. 

There can be multiple CustomLog/TransferLog directives, but OHS will only use the last one found, except in the case of a Virtual Host, which can have its own log file, format, and location.

There is one last important note about the access_log file.  This file constantly grows, because every request received by the server is logged.  To speed this logging, OHS maintains the file offset for the next write.  If you delete the file, OHS will open a new file and write to the stored offset, which means that the new file will start as large as the deleted file but will be totally empty.  To fix this, you must ?reset? the log file by removing it, and then signal OHS using the SIGHUP (-1) signal.

mv access_log access_log.bak
kill ?1 ?cat httpd.pid?

This will move and rename the old access_log file and cause OHS to create a new file when it logs a new request.  The file httpd.pid contains the operating system process id for the parent OHS process.

Aliases

The next section of the httpd.conf file deals with aliases.  OHS uses the module mod_alias to allow the use of directories not under DocumentRoot.  One important note about using aliases is that if they end in a ?/?, then the subdirectory itself is not aliased.  For example, we see below that ?/icons/? is aliased, so a request for //myserver/icons/oracle/OracleWorld.gif will work, but //myserver/icons/OracleWorld.gif will not because of the trailing ?/?.

<IfModule mod_alias.c>
    Alias /icons/ "/home/oracle/oraportal904/Apache/Apache/icons/"
    Alias /jservdocs/ "/home/oracle/oraportal904/Apache/Jserv/docs/"
    Alias /javacachedocs/ "/home/oracle/oraportal904/javacache/javadoc/"
    <IfModule mod_perl.c>
        Alias /perl/ "/home/oracle/oraportal904/Apache/Apache/cgi-bin/"
    </IfModule>
    <Directory "/home/oracle/oraportal904/Apache/Apache/icons">
        Options Indexes MultiViews
        AllowOverride None
        Order allow,deny
        Allow from all
    </Directory>
    ScriptAlias /cgi-bin/ "/home/oracle/oraportal904/Apache/
                          Apache/cgi-bin/"

Another important point is that using aliases opens additional subdirectories for use and thus, may require Directory containers to define access.  If no Directory containers are given for the new locations, then the access will default to the access granted the root ?/? directory. 

ScriptAlias (at the bottom of the example) works in the same manner as Alias, except that OHS will execute the script/application instead of sending it as a page to the requester. 

The AliasMatch directive is not shown in the example but is another powerful tool.  It allows the use of regular expressions instead of just prefix matching.

AliasMatch ^/icons(.*) /usr/local/apache/icons$1

OHS substitutes the parenthesized matches into the string $1 and uses it to identify filenames.

The Redirect directive will take a matching request and send the client a new URL, causing the client to re-request from the new location.

Redirect /joke http://fun.house.com/jokes

Here, a client requesting http://myserver/jokes/good_one.txt would be redirected to http://fun.house.com/jokes/good_one.txt.  To include regular expressions, use the RedirectMatch directive.  The Redirect directive can also contain a status, such as Permanent or 301, Temporary or 302, See Other or 303, or Gone or 410.  In the cases where a document is permanently removed, you would want to use ?gone? and leave off the URL.

Redirect permanent /joke http://fun.house.com/jokes
Redirect 301 /joke http://fun.house.com/jokes
Redirect gone /joke

Indexing and FancyIndexing

The next section of the httpd.conf file deals with indexing.  Indexing in OHS has nothing to do with indexing in an Oracle database. 

When OHS gets a request for a directory, it looks for a file called index.html.  If it is present, then OHS uses it, if it is not present then OHS creates an index or catalog of the directory and serves that.  To create this index, OHS uses the module mod_autoindex.  OHS will not create an index if the Options directive for that directory does not include +Indexes.  The httpd.conf file contains a DirectoryIndex directive that establishes what OHS should do if a request resolves to a directory instead of a file.

<IfModule mod_dir.c>
    DirectoryIndex index.html
</IfModule>

Following this directive, OHS will look for a file called index.html. If it is not present, OHS will check the directory for Options +Indexes and if present, will use mod_autoindex to create a listing of the directory and serve that listing. 

The DirectoryIndex directive can have a list of space-separated files and OHS will attempt to locate each of the files in order before creating its own listing.  If you do not want a server-created listing of the file, you can place an error file at the end of the DirectoryIndex list that will be served if the previous file is not found.

DirectoryIndex index.html welcome.html goodby.html standard/error.html

Once OHS has exhausted the options defined in DirectoryIndex and the directory Options +Indexes is valid, then it must create the index or file list.

One important directive is IndexIgnore.  The IndexIgnore directive allows you to stop mod_autoindex from including certain files, such as backup files or files that begin with a ?dot?, such as the .htaccess file.  Multiple IndexIgnores add files to the exclude list and do not overwrite each other. 

IndexIgnore .htaccess README* *.bak

The httpd.conf file contains a detailed listing for FancyIndexing which creates a format for the OHS generated index listing.  If you wish to modify this listing, please refer to the Apache documentation (Google ?Apache mod_autoindex?). 

 

This is an excerpt from "Oracle 10g Application Server Administration Handbook" by Don Burleson and John Garmany.