|
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. |
|
|
NAME | C SYNOPSIS | PYTHON SYNOPSIS | DESCRIPTION | PYTHON EXAMPLE | DIAGNOSTICS | SEE ALSO | COLOPHON |
|
|
|
PMMERGELABELS(3) Library Functions Manual PMMERGELABELS(3)
pmMergeLabels, pmMergeLabelSets - merge sets of performance metric
labels
#include <pcp/pmapi.h>
int pmMergeLabels(char **sets, int nsets, char *buffer,
int length);
int pmMergeLabelSets(pmLabelSet **sets, int nsets, char *buffer,
int length,
int (*filter)(const pmLabel *, const char *, void *),
void *arg);
cc ... -lpcp
from pcp import pmapi
buffer = pmapi.pmContext().pmMergeLabels(sets)
buffer = pmapi.pmContext().pmMergeLabelSets(sets, filter)
pmMergeLabels takes multiple (nsets) performance metric label sets
and merges them into a single result buffer of length bytes. Both
the input sets and the result buffer are name:value pairs in the
"JSONB" format described on pmLookupLabels(3).
The pmMergeLabelSets interface serves the same purpose, but allows
for indexed sets of labels to be merged. The format of the pmLa‐
belSet data structure is described in detail in pmLookupLabels(3).
Although names may repeat across the provided label sets, dupli‐
cate names are not allowed in the final buffer. Any label names
occurring in more than one of the input label sets are reduced to
one using the rules described in the "PRECEDENCE" section of pm‐
LookupLabels. The position of each element in the sets array is
significant in terms of the precedence rules - earlier positions
are taken to be of lower precedence to later positions.
Values must be primitive JSON entities (e.g. numbers, strings),
one-dimensional arrays or maps (i.e. simple associative arrays).
In addition to using indexed label sets the pmMergeLabelSets in‐
terface provides an optional filter callback function. If non-
NULL, this function will be called for each label that would be
added to the output buffer, allowing finer-grained control over
the final merged set. This mechanism can be used to filter indi‐
vidual labels based on their name, value, and/or flags. If the
filter function returns zero (false), then the given label is fil‐
tered from the resulting set. Any non-zero return value indicates
that the label should be included in the buffer.
import sys
import json
from pcp import pmapi
import cpmapi as c_api
def merge_callback(label, jsondata, data=None):
d = json.loads(jsondata)
labelsD.update(d)
return 0
ctx = pmapi.pmContext()
for metric in sys.argv[1:]:
pmid = ctx.pmLookupName(metric)[0]
lset = ctx.pmLookupLabels(pmid)
labelsD = {}
ctx.pmMergeLabelSets(lset, merge_callback)
print("== %s ===" % metric)
for n,v in labelsD.items():
print(" %s = %s" % (n,v))
ctx.pmFreeLabelSets(lset)
On success, both pmMergeLabels and pmMergeLabelSets returns the
number of bytes written into the supplied buffer.
Failure to parse the input strings, failure to allocate memory, or
any internal inconsistencies found will result in a negative re‐
turn code.
pminfo(1), PMAPI(3) and pmLookupLabels(3).
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 PMMERGELABELS(3)
Pages that refer to this page: pmlookuplabels(3)
|
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. |
|