NAME¶
pmdammv - memory mapped values performance metrics domain agent (PMDA)
SYNOPSIS¶
$PCP_PMDAS_DIR/mmv/pmdammv [
-d domain] [
-l
logfile] [
-U username]
DESCRIPTION¶
pmdammv 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 permanently enabled.
The
mmv PMDA exports instrumentation that has been added to an
application using the MMV APIs (refer to
mmv_stats_init(3) and
mmv(5) for further 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 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 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 created
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 performance
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 creation 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 directories).
The installation process will not overwrite any existing
$PCP_TMP_DIR/mmv
directory. Thus it is possible to implement an alternate 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
pmdammv
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).
SEE ALSO¶
PCPIntro(1),
pmcd(1),
mmv_stats_init(3),
mmv(5),
pcp.conf(5) and
pcp.env(5).