--- name: "pmdaopentelemetry" section: "1" platform: "linux" package: "pcp" version: "7.2.2-2" release: "Arch Linux 2026-11-01" platforms: ["linux"] url: "https://new.carta.tech/pmdaopentelemetry" --- # pmdaopentelemetry(1) OpenTelemetry PMDA ## NAME **pmdaopentelemetry** - OpenTelemetry PMDA ## SYNOPSIS **$PCP\_PMDAS\_DIR/opentelemetry/pmdaopentelemetry** \[**-D** *debug*\] \[**-n**\] \[**-c** *config*\] \[**-d** *domain*\] \[**-l** *logfile*\] \[**-R** *refresh\_timeout*\] \[**-r** *root*\] \[**-t** *timeout*\] \[**-u** *user*\] ## DESCRIPTION **pmdaopentelemetry** is a Performance Metrics Domain Agent (PMDA) which dynamically creates PCP metrics from configured OpenTelemetry endpoints that provide HTTP based access to application metrics. The default *config* directory is **$PCP\_PMDAS\_DIR/opentelemetry/config.d/**, see \`\`CONFIGURATION SOURCES'' below. The default URL fetch *timeout* is **2** seconds. The default *user*, if not specified with the **-u** option, is the "pcp" user. If the **-n** option is given, the list of configuration files will not be sorted prior to processing. This list is sorted by default but that can be expensive if there are a large number of configuration files (URLs and/or scripts). The **-d** option may be used to override the default performance metrics *domain* number, which defaults to **164.** It is strongly recommended not to change this. The *domain* number should be different for every PMDA on the one host, and the same *domain* number should be used for **pmdaopentelemetry** PMDA on all hosts. See also the **-r** option, which allows the root of the dynamic namespace to be changed from the default **opentelemetry**. The **-l** option may be used to specify *logfile* as the destination for PMDA messages instead of the default, **$PCP\_LOG\_DIR/pmcd/opentelemetry.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)](/pmcd/1.md), which may itself have redirected **stderr**. This redirection is normally most useful in a containerized environment, or when using [**dbpmda**(1)](/dbpmda/1.md). The **-r** option allows the root of the dynamic namespace to be changed to *root* from the default, **opentelemetry**. In conjunction with other command line options, this allows **pmdaopentelemetry** 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. The **-R** option allows the user to configure the *timeout*, in seconds, between cluster refreshes. The default value is **10** seconds. ## CONFIGURATION SOURCES As it runs, **pmdaopentelemetry** periodically recursively scans the **$PCP\_PMDAS\_DIR/opentelemetry/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 **pmdaopentelemetry** can reach a OpenTelemetry endpoint. Local file access is also supported with a conventional *file:///somepath/somefile* URL, in which case *somepath/somefile* should contain OpenTelemetry 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 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 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)](/pmLookupLabels/3.md) 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. 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. ## SCRIPTED SOURCES Executable scripts present in the *$PCP\_PMDAS\_DIR/opentelemetry/config.d* directory or sub-directories will be executed and the **stdout** stream containing OpenTelemetry 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/opentelemetry.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)](/sed/1.md), [**awk**(1)](/awk/1.md), or whatever tool is desired. For full details of the OpenTelemetry exposition formats see *https://github.com/open-telemetry/opentelemetry-proto/*\ *blob/main/opentelemetry/proto/metrics/v1/metrics.proto*. ## SELinux CONSIDERATIONS Scripted config files are executed by the **pmdaopentelemetry** PMDA with the same SELinux context and policy as the local [**pmcd**(1)](/pmcd/1.md). For simple scripts, 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)](/audit2allow/1.md) and **semodule**(1). ## METRIC NAMING All metrics from a file named *JOB*.\* will be exported as PCP metrics with the *opentelemetry.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/opentelemetry/config.d/mysource/latency/get.url** will result in metrics being created (by fetching that source URL) below **opentelemetry.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 **opentelemetry** in the PMNS will be updated accordingly, i.e. new metrics will be dynamically added and/or existing metrics removed. In addition, **pmdaopentelemetry** honors the PMCD\_NAMES\_CHANGE [**pmFetch**(3)](/pmFetch/3.md) protocol that was introduced in PCP version 4.0. In particular, if **opentelemetry** metrics are being logged by a PCP version 4.0 or later [**pmlogger**(1)](/pmlogger/1.md), 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 **opentelemetry** PMDA namespace is configured for logging in the **pmlogger** configuration file. See [**pmlogger**(1)](/pmlogger/1.md) for details. An example of such a **pmlogger** configuration file is : ``` log mandatory on 2 second { # log all metrics below the root of the opentelemetry namespace opentelemetry } ``` ## METADATA Metric data returned by URL or scripted configuration files may contain metadata that can be used by the **opentelemetry** PMDA to specify the semantics, data type, scaling and units of dynamically created metrics. This metadata is found for each metric under the **metric** list header in the opentelemetry json data structure. For additional information about PCP metadata, see [**pmLookupDesc**(3)](/pmLookupDesc/3.md) and [**pmParseUnitsStr**(3)](/pmParseUnitsStr/3.md) and examples in shipped configuration files. Metadata must be supplied in the json data by the opentelemetry 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)](/pmParseUnitsStr/3.md),** 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. ## CONTROL METRICS The PMDA maintains special control metrics, as described below. Apart from **opentelemetry.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 **opentelemetry.control.status**, which has a string value. It is important to note that fetching any of the **opentelemetry.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 **opentelemetry.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. - **opentelemetry.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 or an exit code of 0 for scripted sources. This metric can be used for service availability monitoring - provided, as stated above, the corresponding source URL is fetched too. - **opentelemetry.control.status\_code** This metric is similar to **opentelemetry.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. For scripted sources, a **zero** exit code signifies success and any non zero code failure. This metric can also be used for service availability monitoring, with the same caveats as **opentelemetry.control.status**. - **opentelemetry.control.calls** total number of times each configured metric source has been fetched (if it is 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. - **opentelemetry.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. - **opentelemetry.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 **opentelemetry.control.debug** metric has a singular value, defaulting to **0**. If a non-zero value is stored into this metric using [**pmstore**(1)](/pmstore/1.md), additional debug messages will be written to the PMDA log file. ## LIMITATIONS **pmdaopentelemetry** 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 OpenTelemetry PMDA by using the Install script as root: ``` # cd $PCP_PMDAS_DIR/opentelemetry # ./Install ``` To uninstall, the following must be done as root: ``` # cd $PCP_PMDAS_DIR/opentelemetry # ./Remove ``` **pmdaopentelemetry** is launched by [**pmcd**(1)](/pmcd/1.md) and should never be executed directly. The Install and Remove scripts notify **pmcd** when the agent is installed or removed. When scripts and *.url* files are added, removed or changed in the configuration directory, it is usually not necessary to restart the PMDA - the changes will be detected and managed on subsequent requests to the PMDA. ## FILES - **$PCP\_PMDAS\_DIR/opentelemetry/Install** installation script for the **pmdaopentelemetry** agent - **$PCP\_PMDAS\_DIR/opentelemetry/Remove** undo installation script for the **pmdaopentelemetry** agent - **$PCP\_PMDAS\_DIR/opentelemetry/config.d/** contains URLs and scripts used by the **pmdaopentelemetry** agent as sources of opentelemetry metric data. - **$PCP\_LOG\_DIR/pmcd/opentelemetry.log** default log file for error messages from **pmdaopentelemetry** - **$PCP\_VAR\_DIR/config/164.\*** files containing internal tables for metric and instance ID number persistence (domain 164). ## 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 **$PCP\_CONF** variable may be used to specify an alternative configuration file, as described in ## DEBUGGING OPTIONS The **-D** or **--debug** option enables the output of additional diagnostics on the PMDA log file, which is **$PCP\_LOG\_DIR/pmcd/opentelemetry.log** by default (see also **-l** above), to help triage problems, although the information is sometimes cryptic and primarily intended to provide guidance for developers rather than for end-users. *debug* is a comma separated list of debugging options; use [**pmdbg**(1)](/pmdbg/1.md) with the **-l** option to obtain a list of the available debugging options and their meaning. Debugging options specific to **pmdaopentelemetry** are as follows: | | | | --- | --- | | Option | Description | | appl0 | Detailed debugging that is particularly useful for examining the http headers passed to each fetch request, filter settings and other processing details. | In addition, the metric **opentelemetry.control.debug** controls the **appl0** debug setting for a running **pmdaopentelemetry** and this can be changed with the following command:\ **$ pmstore opentelemetry.control.debug** *value*\ where *value* is either **1** (to enable **appl0** diagnostics) or **0** (to disable **appl0** diagnostics). ## SEE ALSO [**PCPIntro**(1)](/PCPIntro/1.md), [**audit2allow**(1)](/audit2allow/1.md), [**pmcd**(1)](/pmcd/1.md), [**pmdaopenmetrics**(1)](/pmdaopenmetrics/1.md), [**pmdbg**(1)](/pmdbg/1.md), [**pminfo**(1)](/pminfo/1.md), [**pmlogger**(1)](/pmlogger/1.md), [**pmstore**(1)](/pmstore/1.md), **semodule**(1), [**PMAPI**(3)](/PMAPI/3.md), [**PMWEBAPI**(3)](/PMWEBAPI/3.md), [**pmFetch**(3)](/pmFetch/3.md) and [**pmLookupLabels**(3)](/pmLookupLabels/3.md).