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PMDAOPENMETRICS(1) General Commands Manual PMDAOPENMETRICS(1)
pmdaopenmetrics - OpenMetrics PMDA
$PCP_PMDAS_DIR/openmetrics/pmdaopenmetrics [-D] [-n] [-c config]
[-d domain] [-l logfile] [-r root] [-t timeout] [-u user]
pmdaopenmetrics is a Performance Metrics Domain Agent (PMDA) which
dynamically creates PCP metrics from configured OpenMetrics
endpoints, which provide HTTP based access to application metrics.
The PMDA essentially implements a bridge between Prometheus and
PCP, allowing PCP to easily ingest performance data from more than
650 registered end-points and many other application specific end-
points.
The default config directory is
$PCP_PMDAS_DIR/openmetrics/config.d/, see ``CONFIGURATION
SOURCES'' below. The default URL fetch timeout is 2 seconds. The
default user, if not specified with the -u option, is the current
user. If the -n option is given, the list of configuration files
will not be sorted prior to processing. This list is sorted by
default but that can be expensive if there are a large number of
configuration files (URLs and/or scripts).
If the -D option is given, additional diagnostic messages will be
written to the PMDA log file, which is
$PCP_LOG_DIR/pmcd/openmetrics.log by default (see also -lbelow).
In addition, the metric openmetrics.control.debug controls the
same debug flag and can be set with the following command:
pmstore openmetrics.control.debug value
where value is either 1 (to enable verbose log messages) or 0 (to
disable verbose log messages). This is particularly useful for
examining the http headers passed to each fetch request, filter
settings and other processing details that are logged when the
debugging flag is enabled.
The -d option may be used to override the default performance
metrics domain number, which defaults to 144. It is strongly
recommended not to change this. The domain number should be
different for every PMDA on the one host, and the same domain
number should be used for pmdaopenmetrics PMDA on all hosts. See
also the -r option, which allows the root of the dynamic namespace
to be changed from the default openmetrics.
The -l option may be used to specify logfile as the destination
for PMDA messages instead of the default,
$PCP_LOG_DIR/pmcd/openmetrics.log. As a special case, logfile may
be "-" to send messages to the stderr stream instead, e.g. -l-.
This would normally be the stderr stream for the parent process,
pmcd(1), which may itself have redirected stderr. This
redirection is normally most useful in a containerized
environment, or when using dbpmda(1).
The -r option allows the root of the dynamic namespace to be
changed to root from the default, openmetrics. In conjunction
with other command line options, this allows pmdaopenmetrics to be
deployed as a different PMDA with distinct metrics namespace and
metrics domain on the same host system. Note that all PMDAs
require a unique domain number so the -d option must also be
specified. Use of the -r option may also change the defaults for
some other command line options, e.g. the default log file name
and the default configuration directory.
As it runs, pmdaopenmetrics periodically recursively scans the
$PCP_PMDAS_DIR/openmetrics/config.d directory (or the directory
specified with the -c option), looking for source URL files
(*.url) and executable scripts or binaries. Any files that do not
have the .url suffix or are not executable, are ignored - this
allows documentation files such as "README" and non-executable
"common" script function definitions to be present without being
considered as config files.
A remote server does not have to be up or stay running - the PMDA
tolerates remote URLs that may come and go over time. The PMDA
will relay data and metadata when/if they are available, and will
return errors when/if they are down. PCP metric IDs, internal and
external instance domain identifiers are persisted and will be
restored when individual metric sources become available and/or
when the PMDA is restarted. In addition, the PMDA checks
directory modification times and will rescan for new or changed
configuration files dynamically. It is not necessary to restart
the PMDA when adding, removing or changing configuration files.
Each file with the .url suffix found in the config directory or
sub-directory contains one complete HTTP or HTTPS URL at which
pmdaopenmetrics can reach a OpenMetrics endpoint. Local file
access is also supported with a conventional
file:///somepath/somefile URL, in which case somepath/somefile
should contain openmetrics formatted metric data.
The first line of a .url config file should be the URL, as
described above. Subsequent lines, if any, are prefixed with a
keyword that can be used to alter the http GET request. A keyword
must end with ':' (colon) and the text extends to the end of the
line. Comment lines that start with # and blank lines are
ignored. The only currently supported keywords are HEADER: and
FILTER:.
HEADER: headername: value ... to end of line
Adds headername and its value to the headers passed in the http
GET request for the configured URL. An example configuration file
that provides 3 commonly used headers and an authentication token
might be :
http://somehost/path/endpoint.html
# this is a comment
HEADER: Accept: text/html
HEADER: Keep-Alive: 300
HEADER: Connection: keep-alive
HEADER: Authorization: token ABCDEF1234567890
As mentioned above, header values extend to the end of the line.
They may contain any valid characters, including colons. Multiple
spaces will be collapsed to a single space, and leading and
trailing spaces are trimmed. A common use for headers is to
configure a proxy agent and the assorted parameters it may
require.
Metric filtering is a configuration file feature that allows
ingested metrics to be included or excluded, i.e. filtered. This
is useful because most end-points return multiple metrics, and
usually only some are interesting for monitoring purposes. The
syntax is:
FILTER: INCLUDE METRIC regex
or
FILTER: EXCLUDE METRIC regex
Dynamically created metric names that match regex will be either
included or excluded in the name space, as specified. Note that
only the PMNS leaf component of the metric name (as ingested from
the URL source) is compared with the regex pattern. The simple
rule is that the first matching filter regex for a particular
metric leaf name is the rule that prevails. If no filter regex
matches (or there are no filters), then the metric is included by
default, i.e. the default filter if none are specified is FILTER:
INCLUDE METRIC .* This is backward compatible with older versions
of the configuration file that did not support filters. Multiple
FILTER: lines would normally be used, e.g. to include some metrics
but exclude all others, use FILTER: EXCLUDE METRIC .* as the last
of several filters that include the desired metrics. Conversely,
to exclude some metrics but include all others, use FILTER:
EXCLUDE METRIC regex. In this case it's not necessary (though
doesn't hurt) to specify the final FILTER: INCLUDE METRIC .*
because, as stated above, any metric that does not match any
filter regex will be included by default.
Label filtering uses similar FILTER: syntax and semantics as
metric filtering. FILTER: EXCLUDE LABEL regex will delete all
labels with label name matching regex from all metrics defined by
the configuration file. The same rules as for metric filters
apply for label filters too - an implicit rule: FILTER: INCLUDE
LABEL .* applies to all labels that do not match any earlier
label filter rule. FILTER: OPTIONAL LABEL regex specifies that
matching label names are to be included in the returned metric
labelsets (i.e. included), but are not to be used as part of the
the external instance names. All included labels that are not
optional (i.e. the intrinsic labels) will be concatenated together
and used for external instance naming. In addition, non-intrinsic
labels (i.e. labels tagged as OPTIONAL) will have the
PM_LABEL_OPTIONAL flag set in the labelsets returned by notes
callbacks. This flag affects how the labels are used in certain
clients. For further details, see pmLookupLabels(3) and related
man pages for further details. Note that external instance names
begin with the unique numeric internal instance identifier
followed by a space, so external instance names are always unique.
Caution is needed with label filtering because by default, all
labels are used to construct the PCP instance name. By excluding
some labels (or changing them to optional), the instance names
will change. In addition, excluding all labels for a particular
metric changes that metric to be singular, i.e. have no instance
domain. By excluding some labels, different instances returned by
the URL or scripted configuration entry for the same metric may
become duplicates. When such duplicates occur, the last duplicate
instance returned by the end-point URL or script prevails over any
earlier instances. For these reasons, it is recommended that
label filtering rules be configured when the configuration file is
first defined, and not changed thereafter. If a label filtering
change is required, the configuration file should be renamed,
which effectively defines a new metric (or set of peer metrics as
returned by the URL or script), with the new (or changed) instance
naming.
Unrecognized keywords in configuration files are reported in the
PMDA log file but otherwise ignored.
Executable scripts present in the
$PCP_PMDAS_DIR/openmetrics/config.d directory or sub-directories
will be executed and the stdout stream containing openmetrics
formatted metric data will be parsed as though it had come from a
URL or file. The stderr stream from a script will be sent to the
PMDA log file, which by default can be found in
$(PCP_LOG_DIR)/pmcd/openmetrics.log.
Note that scripted sources do not support label or metric
filtering (as described above for URL sources) - they can simply
do their own filtering in the script itself with sed(1), awk(1),
or whatever tool is desired.
A simple example of a scripted config entry follows:
#! /bin/sh
awk '{
print("# HELP loadavg local load average")
print("# TYPE loadavg gauge")
printf("loadavg {interval=\"1-minute\"} %.2f\n", $1)
printf("loadavg {interval=\"5-minute\"} %.2f\n", $2)
printf("loadavg {interval=\"15-minute\"} %.2f\n", $3)
}' /proc/loadavg
This script produces the following OpenMetrics-formatted metric
data when run:
# HELP loadavg local load average
# TYPE loadavg gauge
loadavg {interval="1-minute"} 0.12
loadavg {interval="5-minute"} 0.27
loadavg {interval="15-minute"} 0.54
If the above script was saved and made executable in a file named
$PCP_PMDAS_DIR/openmetrics/config.d/local/system.sh then this
would result in a new PCP metric named
openmetrics.local.system.loadavg which would have three instances
for the current load average values: 1-minute, 5-minute and
15-minute.
Scripted config entries may produce more than one PCP leaf metric
name. For example, the above "system.sh" script could also export
other metrics such as CPU statistics, by reading /proc/stat on the
local system. Such additional metrics would appear as peer
metrics in the same PCP metric subtree. In the case of CPU
counters, the metric type definition should be counter, not gauge.
For full details of the openmetrics exposition formats, see
https://github.com/OpenObservability/OpenMetrics/blob/master/specification/OpenMetrics.md .
Scripted config files are executed by the pmdaopenmetrics PMDA
with the same SELinux context and policy as the local pmcd(1).
For simple scripts, such as the load average example described
above, this is normally fine. However AVC errors may result for
scripts that make library or system calls that are restricted by
the prevailing SELinux context and policies. In these cases it is
not feasible to unilaterally grant pmcd or it's PMDAs an
unconfined execution policy. In these site specific cases it will
be necessary to create a local SELinux policy module. This can be
done by capturing the AVC record(s) from the local audit log,
generate a local policy module using audit2allow, and then load
the new module using semodule, e.g. as follows :
$ sudo grep '^type=AVC.*pcp' /var/log/audit/audit.log \
| audit2allow -M mypolicy
$ sudo semodule -i mypolicy.pp
If these local policies need to be persistent across reboots, then
a scriptlet similar to the above example may be added to the local
pmcd RC file (typically /etc/pcp/pmcd/rc.local). For further
details, see audit2allow(1) and semodule(1).
All metrics from a file named JOB.* will be exported as PCP
metrics with the openmetrics.JOB metric name prefix. Therefore,
the JOB name must be a valid non-leaf name for PCP PMNS metric
names. If the JOB name has multiple dot-separated components, the
resulting PMNS names will include those components and care is
needed to ensure there are no overlapping definitions, e.g.
metrics returned by JOB.response may overlap or conflict with
metrics returned by JOB.response.time.
Config file entries (URLs or scripts) found in subdirectories of
the config directory will also result in hierarchical metric
names. For example, a config file named
$PCP_PMDAS_DIR/openmetrics/config.d/mysource/latency/get.url will
result in metrics being created (by fetching that source URL)
below openmetrics.mysource.latency.get in the PCP namespace.
Scripts found in subdirectories of the config directory similarly
result in hierarchical PCP metric names.
As described above, changes and new additions can be made to files
in the configuration directory without having to restart the PMDA.
These changes are detected automatically and the PCP metric names
below openmetrics in the PMNS will be updated accordingly, i.e.
new metrics will be dynamically added and/or existing metrics
removed. In addition, pmdaopenmetrics honors the
PMCD_NAMES_CHANGE pmFetch(3) protocol that was introduced in PCP
version 4.0. In particular, if openmetrics metrics are being
logged by a PCP version 4.0 or later pmlogger(1), new metrics that
appear as a result of changes in the PMDA configuration directory
will automatically start to be logged, provided the root of the
openmetrics PMDA namespace is configured for logging in the
pmlogger configuration file. See pmlogger(1) for details. An
example of such a pmlogger configuration file is :
log mandatory on 2 second {
# log all metrics below the root of the openmetrics namespace
openmetrics
}
Metric data returned by URL or scripted configuration files may
contain metadata that can be used by the openmetrics PMDA to
specify the semantics, data type, scaling and units of dynamically
created metrics. This metadata is prefixed with # PCP5 or # PCP
in the ingested metric data. For additional information about PCP
metadata, see pmLookupDesc(3) and pmParseUnitsStr(3) and examples
in shipped configuration files.
In-line "PCP5" metadata must be supplied by the metrics source
end-point (URL or script). An alternative is to specify this in
the URL configuration file directly, which has the advantage of
not having to modify the source/end-point if the metadata is
incorrect or missing. Metadata specified in the URL configuration
file over-rides any in-line metadata.
The configuration file syntax for specifying metadata is:
METADATA: regex type indom semantics units ... to EOL
Where:
METADATA: is literal
regex is an extended regular expression to match one or more
metric names returned by the URL,
type is one of the PCP numeric types (32, u32, 64, u64, float or
double),
indom is an arbitrary instance domain name, or PM_INDOM_NULL,
semantics is either counter, instant or discrete and
units is either none or a string extending to end of line that is
parsable by pmParseUnitsStr(3), i.e. the units, dimensions and
scaling to be used for matching metrics.
An example configuration file that ingests metrics from the
Grafana /metrics end-point on localhost, filters out all metrics
returned by that URL except for grafana_api_response_status_total
and then specifies the metric type is an unsigned 32 bit integer
with a non-singular instance domain named response and counter
semantics with units of count.
http://localhost:3000/metrics
FILTER: INCLUDE METRIC grafana_api_response_status_total
FILTER: EXCLUDE METRIC .*
METADATA: grafana_api_response_status_total u32 response counter
count
Note that the name in the indom field is presently ignored unless
it is PM_INDOM_NULL, in which case the metric has no instance
domain (i.e. singular), even if it has labels which would
otherwise be used for instance naming.
The PMDA maintains special control metrics, as described below.
Apart from openmetrics.control.debug, each of these metrics has
one instance for each configured metric source. All of these
metrics have integer values with counter semantics, except
openmetrics.control.status, which has a string value. It is
important to note that fetching any of the openmetrics.control
metrics will only update the counters and status values if the
corresponding URL is actually fetched. If the source URL is not
fetched, the control metric values do not trigger a refresh and
the control values reported represent the most recent fetch of
each corresponding source.
The instance domain for the openmetrics.control metrics is
adjusted dynamically as new sources are discovered. If there are
no sources configured, the metric names are still defined but the
instance domain will be empty and a fetch will return no values.
openmetrics.control.status
A string representing the status of the last fetch of the
corresponding source. This will generally be success for
an http response code of 200. This metric can be used for
service availability monitoring - provided, as stated
above, the corresponding source URL is fetched too.
openmetrics.control.status_code
This metric is similar to openmetrics.control.status except
that it is the integer response code of the last fetch. A
value of 200 usually signifies success and any other value
failure. This metric can also be used for service
availability monitoring, with the same caveats as
openmetrics.control.status.
openmetrics.control.calls
total number of times each configured metric source has
been fetched (if it's a URL) or executed (if it's a
script), since the PMDA started. This metric has counter
semantics and would normally be converted to a rate/second
by client tools.
openmetrics.control.fetch_time
Total time in milliseconds that each configured metric
source has taken to return a document, excluding the time
to parse the document. This metric has counter semantics
and would normally be rate converted by client tools but is
also useful in raw form as the accumulated parse time since
the PMDA was started.
openmetrics.control.parse_time
Total time in milliseconds that each configured metric
source has taken to parse each document, excluding the time
to fetch the document. This metric has counter semantics
and would normally be rate converted by client tools but is
also useful in raw form as the accumulated parse time since
the PMDA was started.
When converted to a rate, the calls metric represents the average
fetch rate of each source over the sampling interval (time delta
between samples). The fetch_time and parse_time counters, when
converted to a rate, represent the average fetch and parsing
latency (respectfully), during the sampling interval.
The openmetrics.control.debug metric has a singular value,
defaulting to 0. If a non-zero value is stored into this metric
using pmstore(1), additional debug messages will be written to the
PMDA log file.
pmdaopenmetrics and libpcp internals impose some numerical
constraints about the number of sources (4095), metrics (1024)
within each source, and instances for each metric (4194304).
Install the OpenMetrics PMDA by using the Install script as root:
# cd $PCP_PMDAS_DIR/openmetrics
# ./Install
To uninstall, the following must be done as root:
# cd $PCP_PMDAS_DIR/openmetrics
# ./Remove
pmdaopenmetrics is launched by pmcd(1) and should never be
executed directly. The Install and Remove scripts notify pmcd
when the agent is installed or removed.
When scripts and .url files are added, removed or changed in the
configuration directory, it is usually not necessary to restart
the PMDA - the changes will be detected and managed on subsequent
requests to the PMDA.
$PCP_PMDAS_DIR/openmetrics/Install
installation script for the pmdaopenmetrics agent
$PCP_PMDAS_DIR/openmetrics/Remove
undo installation script for the pmdaopenmetrics agent
$PCP_PMDAS_DIR/openmetrics/config.d/
contains URLs and scripts used by the pmdaopenmetrics agent as
sources of openmetrics metric data.
$PCP_LOG_DIR/pmcd/openmetrics.log
default log file for error messages from pmdaopenmetrics
$PCP_VAR_DIR/config/144.*
files containing internal tables for metric and instance ID
number persistence (domain 144).
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).
PCPIntro(1), audit2allow(1), pmcd(1), pminfo(1), pmlogger(1),
pmstore(1), PMWEBAPI(3), pmFetch(3), pmLookupLabels(3),
semodule(1), and
https://prometheus.io/docs/instrumenting/exposition_formats .
This page is part of the PCP (Performance Co-Pilot) project.
Information about the project can be found at
⟨http://www.pcp.io/⟩. If you have a bug report for this manual
page, send it to pcp@groups.io. This page was obtained from the
project's upstream Git repository
⟨https://github.com/performancecopilot/pcp.git⟩ on 2025-02-02.
(At that time, the date of the most recent commit that was found
in the repository was 2025-01-30.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
Performance Co-Pilot PCP PMDAOPENMETRICS(1)
Pages that refer to this page: htop(1), pmlogger(1), pmdasenderror(3), pmwebapi(3)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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