PMDAMMV(1)PMDAMMV(1)NAMEpmdammv - memory mapped values performance metrics domain agent (PMDA)
SYNOPSIS
$PCP_PMDAS_DIR/mmv/pmdammv [-d domain] [-l logfile] [-U username]
DESCRIPTIONpmdammv is a Performance Metrics Domain Agent (PMDA) which exports
application level performance metrics using memory mapped files. It
offers an extremely low overhead instrumentation facility that is well-
suited to long running, mission critical applications where it is
desirable to have performance metrics and availability information per‐
manently enabled.
The mmv PMDA exports instrumentation that has been added to an applica‐
tion using the MMV APIs (refer to mmv_stats_init(3) and mmv(5) for fur‐
ther details). These APIs can be called from several languages,
including C, C++, Perl, Python and Java (via the separate ``Parfait''
class library).
A brief description of the pmdammv command line options follows:
-d It is absolutely crucial that the performance metrics domain num‐
ber 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 same PMDA on all hosts.
-l Location of the log file. By default, a log file named mmv.log is
written in the current directory of pmcd(1) when pmdammv is
started, i.e. $PCP_LOG_DIR/pmcd. If the log file cannot be cre‐
ated or is not writable, output is written to the standard error
instead.
-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
If you want access to the names, help text and values for the mmv per‐
formance metrics, do the following as root:
# cd $PCP_PMDAS_DIR/mmv
# ./Install
Note that the default mechanism for sharing memory mapped values
between instrumented applications and the mmv PMDA involves the cre‐
ation of a world-writeable $PCP_TMP_DIR/mmv directory with the sticky-
bit set (similar to /tmp and /var/tmp, for example). This suffices to
allow any application, running under any user account, to communicate
with the PMDA (which runs under the "pcp" account by default). This
may not be desirable for every environment, and one should consider the
security implications of any directory setup like this (similar classes
of issues exist as those that affect the system temporary file directo‐
ries).
The installation process will not overwrite any existing
$PCP_TMP_DIR/mmv directory. Thus it is possible to implement an alter‐
nate permissions strategy with no world-writable directory for sharing
files - any directory readable by user or group "pcp" will suffice.
If you want to undo the installation, do the following as root:
# cd $PCP_PMDAS_DIR/mmv
# ./Remove
pmdammv 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.
FILES
$PCP_PMCDCONF_PATH
command line options used to launch pmdammv
$PCP_TMP_DIR/mmv
directory housing memory mapped value files
$PCP_PMDAS_DIR/mmv/help
default help text file for the mmv metrics
$PCP_PMDAS_DIR/mmv/Install
installation script for the pmdammv agent
$PCP_PMDAS_DIR/mmv/Remove
undo installation script for the pmdammv agent
$PCP_LOG_DIR/pmcd/mmv.log
default log file for error messages and other information
from pmdammvPCP 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).
SEE ALSOPCPIntro(1), pmcd(1), mmv_stats_init(3), mmv(5), pcp.conf(5) and
pcp.env(5).
Performance Co-Pilot PCP PMDAMMV(1)
