PMDAPROMETHEUS(1)

NAME
pmdaprometheus - Prometheus PMDA

SYNOPSIS
$PCP_PMDAS_DIR/prometheus/pmdaprometheus [-D] [-n] [-c config] [-t timeout] [-u user]

DESCRIPTION
pmdaprometheus is a Performance Metrics Domain Agent (PMDA) which creates PCP metrics from Prometheus endpoints, which provide HTTP based access to application metrics. The default config directory is $PCP_PMDAS_DIR/prometheus/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/prometheus.log by default. In addition, the metric prometheus.control.debug controls the same debug flag and can be set with the following command:
pmstore prometheus.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.

CONFIGURATION SOURCES
As it runs, pmdaprometheus periodically recursively scans the $PCP_PMDAS_DIR/prometheus/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.

URL SOURCES
Each file with the .url suffix found in the config directory or sub-directory contains one complete HTTP or HTTPS URL at which pmdaprometheus can reach a Prometheus endpoint. Local file access is also supported with a conventional file://somepath/somefile URL, in which case somepath/somefile should contain prometheus 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.

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. The simple rule is that the first matching filter regex for a particular metric 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. FILTER: EXCLUDE LABEL regex will delete all labels matching regex from all metrics defined in the configuration file. The same rules as for metrics apply for labels too - an implicit rule: FILTER: INCLUDE LABEL .* applies to all labels that do not match any earlier filter rule.

Caution is needed with label filtering because by default, all labels are used to construct the PCP instance name. By excluding some labels, the instance names will change. Excluding all labels for a particular metric changes that metric to be singular, i.e. have no instance domain. In addition, by excluding some labels, different instances of the same metric may become duplicates. When such duplicates occur, the last duplicate instance returned by the end-point URL 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, with the new (or changed) instance naming.

Unrecognized keywords in configuration files are reported in the PMDA log file but otherwise ignored.

SCRIPTED SOURCES
Executable scripts present in the $PCP_PMDAS_DIR/prometheus/config.d directory or sub-directories will be executed and the stdout stream containing prometheus 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/prometheus.log.

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 Prometheus-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/prometheus/config.d/local/system.sh then this would result in a new PCP metric named prometheus.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 prometheus exposition formats, see https://prometheus.io/docs/instrumenting/exposition_formats.

METRIC NAMING
All metrics from a file named JOB.* will be exported as PCP metrics with the prometheus.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/prometheus/config.d/mysource/latency/get.url will result in metrics being created (by fetching that source URL) below prometheus.mysource.latency.get in the PCP namespace. Scripts found in subdirectories of the config directory similarly result in hierarchical PCP metric names.

DYNAMIC 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 prometheus in the PMNS will be updated accordingly, i.e. new metrics will be dynamically added and/or existing metrics removed. In addition, pmdaprometheus honors the PMCD_NAMES_CHANGE pmFetch(3) protocol that was introduced in PCP version 4.0. In particular, if prometheus 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 prometheus 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 prometheus namespace
	prometheus
}

CONTROL METRICS
The PMDA maintains special control metrics, as described below. Apart from prometheus.control.debug, each of these metrics is a counter and has one instance for each configured metric source. The instance domain 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.

prometheus.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.

prometheus.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.

prometheus.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.

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 prometheus.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.

LIMITATIONS
pmdaprometheus and libpcp internals impose some numerical constraints about the number of sources (4095), metrics (1024) within each source, and instances for each metric (4194304).

INSTALLATION
Install the Prometheus PMDA by using the Install script as root:

      # cd $PCP_PMDAS_DIR/prometheus
      # ./Install

To uninstall, do the following as root:

      # cd $PCP_PMDAS_DIR/prometheus
      # ./Remove

pmdaprometheus 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.

FILES

$PCP_PMDAS_DIR/prometheus/Install
    installation script for the pmdaprometheus agent

$PCP_PMDAS_DIR/prometheus/Remove
    undo installation script for the pmdaprometheus agent

$PCP_PMDAS_DIR/prometheus/config.d/
    contains URLs and scripts used by the pmdaprometheus agent as sources of prometheus metric data.

$PCP_LOG_DIR/pmcd/prometheus.log
    default log file for error messages from pmdaprometheus

$PCP_VAR_DIR/config/144.*
    files containing internal tables for metric and instance ID number persistence (domain 144).

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
pmcd(1), pminfo(1), pmlogger(1), pmstore(1), PMWEBAPI(3), pmFetch(3) and https://prometheus.io/docs/instrumenting/exposition_formats.