pmLookupName (3) Linux Manual Page

pmLookupName – translate performance metric names into PMIDs

C Synopsis

#include <pcp/pmapi.h>

int pmLookupName(int numpmid, char **namelist, pmID *pmidlist);

cc … -lpcp

Description

Given a list in namelist containing numpmid full pathnames for performance metrics from a Performance Metrics Name Space (PMNS), pmLookupName returns the list of associated Performance Metric Identifiers (PMIDs) via pmidlist.

The result from pmLookupName depends on the presence of any lookup failures, their severity and the number of metrics being looked up.

1.

If there are no lookup failures, the return value will be numpmid.

2.

If a fatal error is encountered, the return value will be less than 0. For example PM_ERR_TOOSMALL, PM_ERR_NOPMNS or PM_ERR_IPC.

3.

If numpmid is greater than one and non-fatal error(s) are encountered, the return value is the number of metric names that have successfully been looked up (greater than or equal to zero and less than or equal to numpmid).

4.

If numpmid is one and a non-fatal error is encountered, the return value is the error code (less than zero).

When errors are encountered, any metrics that cannot be looked up result in the corresponding element of pmidlist being set to PM_ID_NULL.

The slightly convoluted error protocol allows bulk lookups, then probing for more error details in the case of a specific failure, as shown in the EXAMPLES section below.

Note that the error protocol guarantees there is a 1:1 relationship between the elements of namelist and pmidlist, hence both lists contain exactly numpmid elements. For this reason, the caller is expected to have pre-allocated a suitably sized array for pmidlist.

Example

#include <pcp/pmapi.h>

#define NUMPMID 5
char *names[] = {"sample.bin",
                 "sample",
                 "sample.bog",
                 "sample.secret.bar",
                 "sample.secret.bar.bad"};
pmID pmids[NUMPMID];

int main(int argc, char **argv)
{
    int sts;
    int numpmid = NUMPMID;

    pmNewContext(PM_CONTEXT_HOST, "local:");

    sts = pmLookupName(numpmid, names, pmids);

    if (sts < 0) {
        fprintf(stderr, "pmLookupName failed: %s, pmErrStr(sts));
        exit(1);
    }
    if (sts != numpmid) {
        /*
         * some of the lookups failed ... report the reason(s)
         */
        int i;

        for (i = 0; i < numpmid; i++) {
            if (pmids[i] != PM_ID_NULL)
                continue;
            /* this one failed */
            sts = pmLookupName(1, &names[i], &pmids[i]);
            fprintf(stderr, "%s: lookup failed: %s, names[i], pmErrStr(sts));
        }
        exit(1);
    }

    /* all good ... */
    ...
}

See Also

PMAPI(3), pmGetChildren(3), pmGetChildrenStatus(3), pmGetConfig(3), pmLoadNameSpace(3), pmNameID(3), pmNewContext(3), pcp.conf(5) and pcp.env(5).

Diagnostics

PM_ERR_TOOSMALL

numpmid must be at least 1

PM_ERR_NOPMNS

Failed to access a PMNS for operation. Note that if the application hasn’t a priori called pmLoadNameSpace(3) and wants to use the distributed PMNS, then a call to pmLookupName must be made after the creation of a context (see pmNewContext(3)).

PM_ERR_NAME

namelist[0] does not correspond to a valid metric name in the PMNS.

PM_ERR_NONLEAF

namelist[0] refers to a node in the PMNS but it was not a leaf node.

PM_ERR_*

Other diagnostics are for protocol failures when accessing the distributed PMNS.