The configfile specifies which Web servers are to be monitored, their associated access logs and error logs, and a regular-expression based scheme for extracting detailed information about each Web access. This file is maintained as part of the PMDA installation and/or de-installation by the scripts Install and Remove in the directory $PCP_PMDAS_DIR/weblog . For more details, refer to the section below covering installation.
Once started, pmdaweblog monitors a set of log files and in response to a request for information, will process any new information that has been appended to the log files, similar to a tail (1). There is also periodic "catch up" to process new information from all log files, and a scheme to detect the rotation of log files.
Like all other PMDAs, pmdaweblog is launched by pmcd (1) using command line options specified in $PCP_PMCDCONF_PATH - the Install script will prompt for appropriate values for the command line options, and update $PCP_PMCDCONF_PATH .
A brief description of the pmdaweblog command line options follows:
For most installations, the default domain as encapsulated in the file $PCP_PMDAS_DIR/weblog/domain.h will suffice. For alternate values, check $PCP_PMCDCONF_PATH for the domain values already in use on this host, and the file $PCP_VAR_DIR/pmns/stdpmid contains a repository of ``well known'' domain assignments that probably should be avoided.
Collector hosts require the installation of the agent, while monitoring hosts require no agent installation at all.
For collector hosts do the following as root:
# cd $PCP_PMDAS_DIR/weblog # ./Install
The installation procedure prompts for a default or non-default installation. A default installation will search for known server configurations and automatically configure the PMDA for any server log files that are found. A non-default installation will step through each server, prompting the user for other server configurations and arguments to pmdaweblog . The end result of a collector installation is to build a configuration file that is passed to pmdaweblog via the configfile argument.
If you want to undo the installation, do the following as root:
# cd $PCP_PMDAS_DIR/weblog # ./Remove
Regular expressions, which are used on both the access and error log files, must be of the form:
regex regexName regexp or
regex_posix regexName ordering regexp_posix
The regexName is a word which uniquely identifies the regular expression. This is the reference used in the server specification. The regexp for access logs is in the format described for regcmp (3). The regexp_posix for access logs is in the format described for regcomp (3). The argument ordering is explained below. The Posix form should be available on all platforms.
The regular expression requires the specification of up to four arguments to be extracted from each line of a Web server access log, depending on the type of server. In the most common case there are two arguments representing the method and the size.
For the non- Posix version, argument $0 should contain the method: GET , HEAD , POST or PUT . The method PUT is treated as a synonym for POST , and anything else is categorized as OTHER .
The second argument, $1 , should contain the size of the request. A size of `` - '' or `` '' is treated as unknown.
Argument $3 should contain the status code returned to the client browser and argument $4 should contain the status code returned to the server from a remote host. These latter two arguments are used for caching servers and must be specified as a pair (or $3 will be ignored). For further information on status codes, refer to the web site http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html
Some legal non- Posix regex expression specifications for monitoring an access log are:
# pattern for CERN, NCSA, Netscape etc Access Logs regex CERN ] "([A-Za-z][-A-Za-z]+)$0 .*" [-0-9]+ ([-0-9]+)$1 # pattern for FTP Server access logs (normally in SYSLOG) regex SYSLOG_FTP ftpd[.*]: ([gp][-A-Za-z]+)$0( )$1
There is 1 special types of access logs with the RegexName SQUID. This formats extract 4 parameters but since the Squid log file uses text-based status codes, it is handled as a special case.
In the examples below, NS_PROXY parses the Netscape/W3C Common Extended Log Format and SQUID parses the default Squid Object Cache format log file.
# pattern for Netscape Proxy Server Extended Logs regex NS_PROXY ] "([A-Za-z][-A-Za-z]+)$0 .*" ([-0-9]+)$2 \ ([-0-9]+)$1 ([-0-9]+)$3 # pattern for Squid Cache logs regex SQUID [0-9]+.[0-9]+[ ]+[0-9]+ [a-zA-Z0-9.]+ \ ([_A-Z]+)$3/([0-9]+)$2 ([0-9]+)$1 ([A-Z]+)$0
The regexp for the error logs does not require any arguments, only a match. Some legal expressions are:
# pattern for CERN, NCSA, Netscape etc Error Logs regex CERN_err . # pattern for FTP Server error logs (normally in SYSLOG) regex SYSLOG_FTP_err FTP LOGIN FAILED
If POSIX compliant regular expressions are used, additional information is required since the order of parameters cannot be specified in the regular expression. For backwards compatibility, the common case of two parameters the order may be specified as method,size or size,method In the general case, the ordering is specified by one of the following methods:
As for the non- Posix format, the SQUID RegexName is treated as a special case to match the non-numerical status codes.
Some legal Posix regex expression specifications for monitoring an access log are:
# pattern for CERN, NCSA, Netscape, Apache etc Access Logs regex_posix CERN method,size ][ \]+"([A-Za-z][-A-Za-z]+) \ [^"]*" [-0-9]+ ([-0-9]+) # pattern for CERN, NCSA, Netscape, Apache etc Access Logs regex_posix CERN 1,2 ][ \]+"([A-Za-z][-A-Za-z]+) \ [^"]*" [-0-9]+ ([-0-9]+) # pattern for FTP Server access logs (normally in SYSLOG) regex_posix SYSLOG_FTP method,size ftpd[.*]: \ ([gp][-A-Za-z]+)( ) # pattern for Netscape Proxy Server Extended Logs regex_posix NS_PROXY 1,3,2,4 ][ ]+"([A-Za-z][-A-Za-z]+) \ [^"]*" ([-0-9]+) ([-0-9]+) ([-0-9]+) # pattern for Squid Cache logs regex_posix SQUID 4,3,2,1 [0-9]+.[0-9]+[ ]+[0-9]+ \ [a-zA-Z0-9.]+ ([_A-Z]+)/([0-9]+) ([0-9]+) ([A-Z]+) # pattern for CERN, NCSA, Netscape etc Error Logs regex_posix CERN_err - . # pattern for FTP Server error logs (normally in SYSLOG) regex_posix SYSLOG_FTP_err - FTP LOGIN FAILED
A Web server can be specified using this syntax:
server serverName on|off accessRegex accessFile errorRegex errorFile
The serverName must be unique for each server, and is the name given to the instance for the associated performance metrics. See PMAPI (3) for a discussion of PCP instance domains. The on or off flag indicates whether the server is to be monitored when the PMDA is installed. This can altered dynamically using pmstore (1) for the metric web.perserver.watched , which has one instance for each Web server named in configfile .
Two files are monitored for each Web server, the access and the error log. Each file requires the name of a previously declared regular expression, and a file name. The log files specified for each server do not have to exist when the weblog PMDA is installed. The PMDA will continue to check for non-existent log files and open them when possible. Some legal server specifications are:
# Netscape Server on Port 80 at IP address 127.55.555.555 server 127.55.555.555:80 on CERN /logs/access CERN_err /logs/errors # FTP Server. server ftpd on SYSLOG_FTP /var/log/messages SYSLOG_FTP_err /var/log/messages