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NAME | C SYNOPSIS | DESCRIPTION | LABEL SYNTAX | PRECEDENCE | DATA STRUCTURES | EXAMPLES | DIAGNOSTICS | SEE ALSO | COLOPHON |
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PMLOOKUPLABELS(3) Library Functions Manual PMLOOKUPLABELS(3)
pmLookupLabels, pmGetInstancesLabels, pmGetItemLabels, pmGetCluster‐
Labels, pmGetInDomLabels, pmGetDomainLabels, pmGetContextLabels -
retrieve labels associated with performance metric values
#include <pcp/pmapi.h>
int pmLookupLabels(pmID pmid, pmLabelSet **labelsets);
int pmGetInstancesLabels(pmInDom indom, pmLabelSet **labelsets);
int pmGetItemLabels(pmID pmid, pmLabelSet **labelsets);
int pmGetClusterLabels(pmID pmid, pmLabelSet **labelsets);
int pmGetInDomLabels(pmInDom indom, pmLabelSet **labelsets);
int pmGetDomainLabels(int domain, pmLabelSet **labelsets);
int pmGetContextLabels(pmLabelSet **labelsets);
cc ... -lpcp
Labels are name:value pairs associated with performance metric values
for the purpose of attaching additional metric metadata to values.
This metadata is less structured and exists separately to the metric
descriptor available for every PCP metric from pmLookupDesc(3).
Much like the metric descriptor metadata, labels are an integral part
of the identity of each metric, and should rarely, if ever, change.
The pmLookupLabels routine is a convenience interface providing
retrieval for all labels associated with a single performance metric
identifier, pmid. It performs no caching of labels internally.
For efficiency in communication and storage within the various
components of the PMCS (Performance Metrics Collection System),
labels are maintained using a hierarchy. The set of labels
associated with any individual metric value consists of the union of
labels from each of these sets of labels:
1. Global labels (apply to all metric values from a host or archive
context)
pmGetContextLabels
provides the labelset associated with all metric values from
a given source (PMAPI context).
2. Domain labels (apply to every metric within a PMDA)
pmGetDomainLabels
provides the labelset associated with the domain identifier.
3. Instance Domain labels (apply to all metrics sharing that indom)
pmGetInDomLabels
provides the labelset associated with the instance domain
identifier indom.
4. Cluster labels (apply to a group of metrics within one domain)
pmGetClusterLabels
provides the labelset associated with the metric cluster
(domain,cluster) identified by pmid.
5. Item labels (apply to an individual performance metric)
pmGetItemLabels
provides the labelset associated with the metric item
(domain,cluster,item) identified by pmid.
6. Instance labels (apply to individual instances of a metric)
pmGetInstancesLabels
provides the set of instance identifiers and labels in
labelsets for each instance associated with the instance
domain identifier indom. The return value indicates the
number of elements in the result - one labelset for each
instance.
These independent labelsets can be merged using pmMergeLabelSets(3)
to form the complete set of all labels associated with a given value.
Labels are stored and communicated within PCP using JSONB format.
This format is a restricted form of JSON suitable for indexing and
other operations. In JSONB form, insignificant whitespace is
discarded, and the order of label names is not preserved. Within the
PMCS a lexicographically sorted key space is always maintained,
however. Duplicate label names are not permitted. The label with
highest precedence is the only one presented. If duplicate names are
presented at the same hierarchy level, only one will be preserved
(exactly which one wins is arbitrary, so do not rely on this).
All name:value pair(s) present will be converted to JSONB form and
merged with the existing set of labels for the requested entity
(context, domain, indom, metric or instance).
The label names are further constrained to the same set of rules
defined for PMNS subtree names.
Each component in a label name must begin with an alphabetic
character, and be followed by zero or more characters drawn from the
alphabetics, the digits and the underscore (``_'') character. For
alphabetic characters in a name, upper and lower case are
distinguished.
The value of a label offers significantly more freedom, and may be
any valid value as defined by the JSON (http://json.org )
specification. Redundant whitespace is always removed within the
PMCS.
The complete set of labels associated with any metric value is built
from several sources and duplicate label names may exist at any point
in the source hierarchy. However, when evaluating the label set
(merging labels from the different sources) the JSONB concept of only
presenting unique labels is used. It is therefore important to
define precedence rules in order that a deterministic set of uniquely
named labels can be defined.
As a rule of thumb, the labels closest to PMNS leaf nodes and metric
values take precedence:
1. Global context labels
(as reported by the pmcd.labels metric) are the lowest
precedence.
2. Domain labels
(for all values from a PMDA) are the next highest precedence.
3. Instance Domain Labels
associated with an InDom are the next highest precedence.
4. Metric cluster labels
associated with a PMID cluster are the next highest precedence.
5. Metric item labels
associated with an individual PMID are the next highest
precedence.
6. Instance labels
associated with a metric instance identifier have highest
precedence.
The primary output from pmLookupLabels is returned in the argument
labelset as an array, using the following component data structures;
struct {
uint name : 16; /* label name offset in JSONB string */
uint namelen : 8; /* length of name excluding the null */
uint flags : 8; /* information about this label */
uint value : 16; /* offset of the label value */
uint valuelen : 16; /* length of value in bytes */
} pmLabel;
struct {
uint inst; /* PM_IN_NULL or the instance ID */
int nlabels; /* count of labels or error code */
char *json; /* JSON formatted labels string */
uint jsonlen : 16; /* JSON string length byte count */
uint padding : 16; /* zero, reserved for future use */
pmLabel *labels; /* indexing into the JSON string */
} pmLabelSet;
The pmLabel provides information about an individual label. This
includes the offsets to the start of its name and value in the json
string of a pmLabelSet, their respective lengths, and also any
informative flags associated with the label (describing where it lies
in the hierarchy of labels, and whether it is an intrinsic or
extrinsic label).
Building on this, the pmLabelSet provides information about the set
of labels associated with an entity (context, domain, indom, metric
or instance). The entity will be from any one level of the label
hierarchy. If at the lowest hierarchy level (which happens to be
highest precedence - PM_LABEL_INSTANCES) then the inst field will
contain an actual instance identifier instead of PM_IN_NULL.
The nlabels field describes the number of labels (name:value pairs)
that can be found in both the accompanying json string (which is
JSONB format - no unnecessary whitespace and with no duplicate label
names) and the accompanying labels array (which has nlabels
elements).
Consider a deployment with global labels (assume $PCP_SYSCONF_DIR is
set to its usual location of /etc/pcp) as follows:
$ cat /etc/pcp/labels/*
{
"tier": "production",
"datacenter": "hkg",
"services": ["indexer","database"]
}
Use pminfo to form the merged labelsets for several pmdasample(1)
metrics as follows:
$ pminfo -m -f --labels sample.rapid sample.colour sample.mirage
sample.rapid PMID: 30.0.64
value 800000000
labels {"agent":"sample","datacenter":"sydney","hostname":"acme.com","measure":"speed","role":"testing","services":["indexer","database"],"tier":"production","units":"metres per second","unitsystem":"SI"}
sample.colour PMID: 30.0.5
inst [0 or "red"] value 101
inst [1 or "green"] value 202
inst [2 or "blue"] value 303
inst [0 or "red"] labels {"agent":"sample","datacenter":"syd","hostname":"acme.com","model":"RGB","role":"testing","services":["indexer","database"],"tier":"production"}
inst [1 or "green"] labels {"agent":"sample","datacenter":"syd","hostname":"acme.com","model":"RGB","role":"testing","services":["indexer","database"],"tier":"production"}
inst [2 or "blue"] labels {"agent":"sample","datacenter":"syd","hostname":"acme.com","model":"RGB","role":"testing","services":["indexer","database"],"tier":"production"}
sample.mirage PMID: 29.0.37
inst [0 or "m-00"] value 99
inst [0 or "m-00"] labels {"agent":"sample","datacenter":"sydney","hostname":"acme.com","role":"testing","services":["indexer","database"],"tier":"production","transient":false}
Here, pminfo has merged the separate sets of labels returned from
pmGetContextLabels (names: datacenter, hostname, services, tier),
pmGetDomainLabels (names: role, agent), pmGetInDomLabels (names:
model), pmGetItemLabels (names: units, unitsystem) and
pmGetInstancesLabels (names: transient) to form the complete set for
each of the metrics.
On success these interfaces all return the number of elements in the
labelsets array. associated with performance metrics. The memory
associated with labelsets should be released using pmFreeLabelSets(3)
when no longer needed.
Only in the case of pmLookupLabels will the resulting labelset be a
merged set of labels from all hierarchy levels.
For the other routines, except for pmGetInstancesLabels, if no labels
exist at all for the requested hierarchy level the return code will
be zero and no space will have been allocated.
In the case of pmGetInstancesLabels, which can return multiple
elements in its labelsets result (one set of labels for each
instance), the nlabels field may be either zero indicating no labels
for that instance, or a positive count of labels, or a negative PMAPI
error code.
Note that it is mandatory for a call to pmGetInstancesLabels to be
preceded by a call to pmGetInDom(3) to ensure the instances have been
resolved within the PMDA.
If no result can be obtained, e.g. due to IPC failure using the
current PMAPI context then pmGetInstancesLabels will return a
negative error code which may be examined using pmErrStr(3).
pmcd(1), PMAPI(3), pmFetch(3), pmGetInDom(3), pmLookupDesc(3),
pmLookupName(3), pmFreeLabelSets(3), pmMergeLabelSets(3) and
pmNewContext(3).
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
2018-02-02. (At that time, the date of the most recent commit that
was found in the repository was 2018-02-02.) 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 PMLOOKUPLABELS(3)
Pages that refer to this page: pmdumplog(1), pminfo(1), pmapi(3), pmdalabel(3), pmfetch(3), pmfreelabelsets(3), pmmergelabels(3), pmprintlabelsets(3), LOGARCHIVE(5)
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