Ubuntu Manpage: pmdaweblog - performance metrics domain agent (PMDA) for Web server logs

NAME

       pmdaweblog - performance metrics domain agent (PMDA) for Web server logs

SYNOPSIS

       $PCP_PMDAS_DIR/weblog/pmdaweblog  [-Cp]  [-d  domain] [-h helpfile] [-i port] [-l logfile]
       [-n idlesec] [-S num] [-t delay] [-u socket] [-U username] configfile

DESCRIPTION

pmdaweblog is a Performance Metrics Domain Agent (PMDA(3)) that scans Web server logs to
extract metrics characterizing Web server activity. These performance metrics are then
made available through the infrastructure of the Performance Co-Pilot (PCP).

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:

-C Check the configuration and exit.

-d domain
Specify the domain number. It is absolutely crucial that the performance metrics
domain number specified here is unique and consistent. That is, domain should be
different for every PMDA on the one host, and the same domain number should be used
for the pmdaweblog PMDA on all hosts.

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.

-h helpfile
Get the help text from the supplied helpfile rather than from the default location.

-i port
Communicate with pmcd(1) on the specified Internet port (which may be a number or a
name).

-l logfile
Location of the log file. By default, a log file named weblog.log is written in
the current directory of pmcd(1) when pmdaweblog is started, i.e.
$PCP_LOG_DIR/pmcd. If the log file cannot be created or is not writable, output is
written to the standard error instead.

-n idlesec
If a Web server log file has not been modified for idlesec seconds, then the file
will be closed and re-opened. This is the only way pmdaweblog can detect any
asynchronous rotation of the logs by Web server administrative scripts. The
default period is 20 seconds. This value may be changed dynamically using
pmstore(1) to modify the value of the performance metric web.config.check.

-p Communicate with pmcd(1) via a pipe.

-S num Specify the maximum number of Web servers per sproc. It may be desirable (from a
latency and load balancing perspective) or necessary (due to file descriptor
limits) to delegate responsibility for scanning the Web server log files to several
sprocs. pmdaweblog will ensure that each sproc handles the log files for at most
num Web servers. The default value is 80 Web servers per sproc.

-t delay
To avoid the need to scan a lot of information from the Web server logs in response
to a single request for performance metrics, all log files will be checked at least
once every delay seconds. The default is 15 seconds. This value may by changed
dynamically using pmstore(1) to modify the value of the performance metric
web.config.catchup.

-u socket
Communicate with pmcd(1) via the given Unix domain socket.

-U User account under which to run the agent. The default is the unprivileged "pcp"
account in current versions of PCP, but in older versions the superuser account
("root") was used by default.

INSTALLATION

       The  PCP  framework allows metrics to be collected on one host and monitored from another.
       These hosts are referred to as collector and monitor hosts, respectively.  A host  may  be
       both a collector and a monitor.

       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

       pmdaweblog  is launched by pmcd(1) and should never be executed directly.  The Install and
       Remove scripts notify pmcd(1) when the agent is installed or removed.

CONFIGURATION

       The configuration file for the weblog PMDA is an ASCII file that can be  easily  modified.
       Empty  lines  and  lines beginning with '#' are ignored.  All other lines must be either a
       regular expression or server specification.

       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:

       n1,n2,n3,n4
            where nX is a digit between 1 and 4. Each comma-seperated field represents (in order)
            the argument number for method,size,client_status,server_status

       -    Used for cases like the error logs where the content is ignored.

       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

CAVEATS

       Specifying regular expressions with an incorrect number of arguments, anything other  than
       2  for  access logs, and none for error logs, may cause the PMDA to behave incorrectly and
       even crash. This is due to limitations in the interface of regex(3).

FILES

       $PCP_PMDAS_DIR/weblog
                 installation directory for the weblog PMDA

       $PCP_PMDAS_DIR/weblog/Install
                 installation script for the weblog PMDA

       $PCP_PMDAS_DIR/weblog/Remove
                 de-installation script for the weblog PMDA

       $PCP_LOG_DIR/pmcd/weblog.log
                 default log file for error reporting

       $PCP_PMCDCONF_PATH
                 pmcd configuration file that specifies the command line options to be used  when
                 pmdaweblog is launched

       $PCP_LOG_DIR/NOTICES
                 log of PMDA installations and removals

       $PCP_VAR_DIR/config/web/weblog.conf
                 likely location of the weblog PMDA configuration file

       $PCP_DOC_DIR/pcpweb/index.html
                 the online HTML documentation for PCPWEB

PCP ENVIRONMENT

       Environment variables with the prefix PCP_ are used to parameterize the file and directory
       names used by PCP.  On each installation, the file /etc/pcp.conf contains the local values
       for  these  variables.   The  $PCP_CONF  variable  may  be  used to specify an alternative
       configuration file, as described in pcp.conf(5).