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NAME | C SYNOPSIS | DESCRIPTION | DIAGNOSTICS | FILES | SEE ALSO | COLOPHON |
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PMDISCOVERSETUP(3) Library Functions Manual PMDISCOVERSETUP(3)
pmDiscoverSetup, pmDiscoverSetSlots, pmDiscoverSetEventLoop,
pmDiscoverSetConfiguration, pmDiscoverSetMetricRegistry,
pmDiscoverClose - asynchronous archive location and contents
discovery services
#include <pcp/pmwebapi.h>
int pmDiscoverSetup(pmDiscoverModule *module,
pmDiscoverCallBacks *callbacks, void *arg);
int pmDiscoverSetSlots(pmDiscoverModule *module, void *slots);
int pmDiscoverSetEventLoop(pmDiscoverModule *module, void
*uvloop);
int pmDiscoverSetConfiguration(pmDiscoverModule *module,
struct dict *config);
int pmDiscoverSetMetricRegistry(pmDiscoverModule *module,
struct mmv_registry *registry);
int pmDiscoverClose(pmDiscoverModule *module);
cc ... -lpcp_web
The pmDiscoverSetup and related functions are an integral part of
the libpcp_web API library, as used by and described in
pmwebapi(3), pmproxy(1), pmseries(1) and elsewhere. These func‐
tions provide an asynchronous event driven mechanism to automati‐
cally discover PCP archives created by pmlogger(1) and any other
application capable of writing PCP archives. This includes
pmrep(1) and other applications using the LOGIMPORT(3) API for im‐
porting performance data into the PCP infrastructure and writing
PCP archives.
The pmDiscover API services dynamically discover, monitor and man‐
age directories of PCP archives as they are created, written to,
compressed and eventually deleted. The underlying archive life-
cycle is normally managed by the PCP archive management infra‐
structure (see pmlogger_daily(1)). Discovered archives that are
active (currently being written) are "log-tailed" to extract near
live/real-time performance data which is then passed off via reg‐
istered callbacks for further processing, e.g. to add the data to
a key-value server. Archives that are compressed or inactive are
tracked/monitored but not log-tailed - this is because compressed
archives never grow and so log-tailing would never discover any
new data. See the --load option in pmseries(1) for a supported
mechanism for ingesting previously collected (inctive) PCP
archives, whether compressed or not, into a key-value server.
The pmDiscover routines can be configured to automatically discov‐
er and monitor PCP archives in one or more directories as speci‐
fied in the pmDiscoverModule, which is initially set up by calling
pmDiscoverSetConfiguration to create a module of type pmDiscover‐
Module, as described above. The resulting module is then passed
to pmDiscoverSetup along with an initialized structure of call‐
backs of type pmDiscoverCallBacks.
Setting up a discovery module and callbacks would normally declare
an instance of pmDiscoverSettings, e.g.
#include <pcp/pmwebapi.h>
static pmDiscoverSettings someapp_discover = {
.callbacks.on_source = pmSomeappDiscoverSource,
.callbacks.on_closed = pmSomeappDiscoverClosed,
.callbacks.on_labels = pmSomeappDiscoverLabels,
.callbacks.on_metric = pmSomeappDiscoverMetric,
.callbacks.on_values = pmSomeappDiscoverValues,
.callbacks.on_indom = pmSomeappDiscoverInDom,
.callbacks.on_text = pmSomeappDiscoverText,
.module.on_info = someapp_logging_function,
};
And then initialize this with API calls similar to the following:
pmDiscoverSetEventLoop(&someapp_discover.module, myevents);
pmDiscoverSetConfiguration(&someapp_discover.module, myconfig);
pmDiscoverSetMetricRegistry(&someapp_discover.module, metric_registry);
pmDiscoverSetup(&someapp_discover.module, &someapp_discover.callbacks, &privatedata);
The above code must then implement each of the declared callbacks
etc. to do whatever is required with the data passed in to the
callback. Prototypes for these callbacks can be found in the
pmwebapi.h header. The callbacks will be made asynchronously, as
archives are discovered or deleted and as new data is written to
active archive volume and metadata files.
In the case of pmproxy(1), callbacks are registered to capture
performance data, which is then sent to a key-value server for
fast scalable time-series queries by clients of the PMWEBAPI(3)
REST API services. Such clients include the pmseries(1) applica‐
tion and pmproxy(1), which is the back-end REST API server for
grafana-pcp, a native grafana-server(1) data-source for PCP.
Generally zero on success, or on error a negative return code, see
pmerr(1).
The default archive directory is $PCP_ARCHIVE_DIR, which is nor‐
mally /var/log/pcp/pmlogger. The API recursively descends all
sub-directories and also dynamically discovers any new directories
or archives found therein.
grafana-server(1), pmerr(1), pmlogger(1), pmproxy(1), pmseries(1),
PMWEBAPI(3), mmv_stats_registry(3), PMAPI(3), pmErrStr(3),
pcp.conf(5) and pcp.env(5).
This page is part of the PCP (Performance Co-Pilot) project. In‐
formation about the project can be found at ⟨http://www.pcp.io/⟩.
If you have a bug report for this manual page, send it to
[email protected]. This page was obtained from the project's upstream
Git repository ⟨https://github.com/performancecopilot/pcp.git⟩ on
2025-08-11. (At that time, the date of the most recent commit
that was found in the repository was 2025-08-11.) 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 [email protected]
Performance Co-Pilot PCP PMDISCOVERSETUP(3)
Pages that refer to this page: pmseriesquery(3)
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HTML rendering created 2025-09-06 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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