MMV_STATS_INIT(3)

NAME
mmv_stats_init, mmv_stats2_init - create and initialize Memory Mapped Value file

C SYNOPSIS
#include <pcp/pmapi.h>
#include <pcp/mmv_stats.h>

void *mmv_stats_init(const char *name, int cluster, mmv_stats_flags_t flags, const mmv_metric_t *stats, int nstats, mmv_indom_t *indoms, int nindoms);
void *mmv_stats2_init(const char *name, int cluster, mmv_stats_flags_t flags, const mmv_metric2_t *stats2, int nstats2, mmv_indom2_t *indoms2, int nindoms2);

cc ... -lpcp_mmv -lpcp

DESCRIPTION

mmv_stats_init creates and initializes the content of the MMV(5) file, returning a handle that is used in subsequent MMV API calls.

mmv_stats2_init is equivalent to mmv_stats_init except that it provides an option for longer metric and instance names.

mmv_stats_stop performs an orderly shutdown of the mapping handle returned by an earlier initialization call.

The file is created in the $PCP_TMP_DIR/mmv directory, name argument is expected to be a basename of the file, not the full path. The metadata content of the file does not change after the file has been created.

The old file is removed unconditionally unless there was an error.

cluster is the preferred MMV PMDA cluster ID to be used for the metrics originating from this call to mmv_stats_init. The flags provide additional control over the behaviour of the MMV PMDA - e.g. use of MMV_FLAG_PROCESS will ensure values are only exported when the instrumented application is running - this is verified on each request for new values.

stats is the array of mmv_metric_t elements of length nstats. Each element of the array describes one PCP metric.

        typedef struct {
            char name[MMV_NAMEMAX];     /* Name of the metric */
            __uint32_t item;            /* Item component of PMID */
            mmv_metric_type_t type;     /* Type of the metric */
            mmv_metric_sem_t semantics; /* Semantics of the metric */
            pmUnits dimension;          /* Dimensions (TIME,SPACE,etc) */
            __uint32_t indom;           /* Instance domain identifier */
            char *shorttext;            /* Optional, one-line help */
            char *helptext;             /* Optional, full help text */
        } mmv_metric_t;

stats2 is the array of mmv_metric2_t elements of length nstats2. Each element of the array describes one PCP metric, the only difference to stats is the lifting of the restriction on name length (previously MMV_NAMEMAX, which is 64 bytes).

        typedef struct {
            char *name;                 /* Name of the metric */
            __uint32_t item;            /* Item component of PMID */
            mmv_metric_type_t type;     /* Type of the metric */
            mmv_metric_sem_t semantics; /* Semantics of the metric */
            pmUnits dimension;          /* Dimensions (TIME,SPACE,etc) */
            __uint32_t indom;           /* Instance domain identifier */
            char *shorttext;            /* Optional, one-line help */
            char *helptext;             /* Optional, full help text */
        } mmv_metric_t;

If indom is not zero and not PM_INDOM_NULL, then the metric has multiple values and there must be a corresponding indom entry in the indom list (uniquely identified by serial number).

The stats and stats2 arrays cannot contain any elements which have no name - this is considered an error and no metrics will be exported in this case.

indoms is the array of mmv_indom_t elements of length nindoms. Each element of the array describes one PCP instance domain.

        typedef struct {
            __int32_t internal;
            char external[MMV_NAMEMAX];
        } mmv_instances_t;
        typedef struct {
            __uint32_t serial;           /* Unique serial number */
            __uint32_t count;            /* Number of instances */
            mmv_instances_t *instances;  /* Internal/external IDs */
            char *shorttext;             /* Short help text */
            char *helptext;              /* Long help text */
        } mmv_indom_t;

indoms2 is the array of mmv_indom2_t elements of length nindoms2. Each element of the array describes one PCP instance domain, and the only difference to indoms is the lifting of the restriction on external instance name lengths (previously MMV_NAMEMAX, which is 64 bytes).

        typedef struct {
            __int32_t internal;
            char *external;
        } mmv_instances2_t;
        typedef struct {
            __uint32_t serial;           /* Unique serial number */
            __uint32_t count;            /* Number of instances */
            mmv_instances2_t *instances; /* Internal/external IDs */
            char *shorttext;             /* Short help text */
            char *helptext;              /* Long help text */
        } mmv_indom2_t;

RETURN VALUES
These functions return the address of the memory mapped region on success. On failure, NULL is returned and errno is set to a value suitable for decoding with strerror(3).

SEE ALSO
mmv_inc_value(3), mmv_lookup_value_desc(3), strerror(3) and mmv(5).