mmv_stats_registry(3) — Linux manual page


MMV_STATS_REGISTRY(3)   Library Functions Manual   MMV_STATS_REGISTRY(3)

NAME         top

       mmv_stats_registry, mmv_stats_start, mmv_stats_stop - Initialize
       the Memory Mapped Value file

C SYNOPSIS         top

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

       mmv_registry_t *mmv_stats_registry(const char *file, int cluster,
                                           mmv_stats_flags_t flags);

       void *mmv_stats_start(mmv_registry_t *registry);
       void  mmv_stats_stop(const char *fname, void *addr);

       cc ... -lpcp_mmv -lpcp

DESCRIPTION         top

       mmv_stats_registry initializes an opaque structure that defines
       various aspects of a memory mapped file.  This file is used for
       lightweight interprocess communication between an instrumented
       application and pmdammv(1).

       The mmv_stats_registry interface is used to allocate a registry,
       and allows the name of the MMV(5) file, the cluster identifier
       and the flags (if any) to be set.  It returns a handle that is
       used in subsequent MMV API calls when adding metrics, indoms,
       instances and labels to the registry - before actually creating
       the file.

       mmv_stats_start is the call that creates the MMV(5) file with the
       handle that returns mmv_stats_registry.  It returns the mapped
       memory handle used in subsequent MMV API calls, such as

       mmv_stats_stop performs an orderly shutdown of the mapping handle
       returned by an earlier initialization call and also frees the
       registry structure.

       The combination of mmv_stats_registry and mmv_stats_start do the
       same as the deprecated calls mmv_stats(2)_init.  However, now,
       one should first call mmv_stats_registry and then the API calls
       that add instances, indoms, metrics and labels.  In this way,
       there is no need to know in advance which version of the
       MMV(1|2|3) mapping will be used as it is calculated

       The file is created in the $PCP_TMP_DIR/mmv directory, the 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

       cluster is the preferred MMV PMDA cluster ID to be used for the
       metrics the originates the call mmv_stats_start.  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.

       The next sections explain how to add metrics, indoms, instances
       and labels.

ADD METRICS         top

       int mmv_stats_add_metric(mmv_registry_t *registry,
       const char *name, int item,
                               mmv_metric_type_t type, mmv_metric_sem_t
       sem, pmUnits units,
                               int serial, const char *shorthelp,
       const char *longhelp);

       When adding a metric, internally it is being handled using the
       next struct.  sem match in the struct is semantics. units match
       in the struct is dimension. serial match in the struct is indom.

               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_metric2_t;

ADD INDOMS         top

       int mmv_stats_add_indom(mmv_registry_t *registry, int serial,
                               const char *shorthelp,
       const char *longhelp);

       When adding an indom, internally it is being handled using the
       next struct.

               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;

ADD INSTANCES         top

       int mmv_stats_add_instance(mmv_registry_t *registry, int serial,
                                  int instid, const char *instname);

       When adding an instance, internally it is being handled using the
       next struct.  instid match in the struct is internal while
       instname is external.

               typedef struct {
                   __int32_t internal;
                   char *external;
               } mmv_instances2_t;

       It is worth mentioning that if the indom of the instance is not
       found it returns an error.

ADD LABELS         top

       int mmv_stats_add_registry_label(mmv_registry_t *registry,
                                        const char *name, const char
                                        mmv_value_type_t type, int

       int mmv_stats_add_indom_label(mmv_registry_t *registry, int
                                     const char *name, const char
                                     mmv_value_type_t type, int

       int mmv_stats_add_metric_label(mmv_registry_t *registry, int
                                      const char *name, const char
                                      mmv_value_type_t type, int

       int mmv_stats_add_instance_label(mmv_registry_t *registry, int
                                        int instid, const char *name,
               const char *value,
                                        mmv_value_type_t type, int

       registry is the handle obtained from mmv_stats_registry. name and
               value are the strings that will form the label.

       type specifies the value type that can be: MMV_STRING_TYPE,
       and MMV_MAP_TYPE.

       At the moment there is a simple check of the correctness of the
       value.  After adding a label, it is called a function to verify
       if it is correct.

       Additionally, if optional is set, it is added the flag

       serial is the serial of the indom when adding an indom or
       instance label.  item is the metric identifier when adding a
       metric label. Finally, when adding a registry label it is not
       necessary to give the cluster id because it will be taken from
       the internal registry struct already created.

       mmv_stats_add_registry_label adds a PM_LABEL_CLUSTER.

       mmv_stats_add_indom_label adds a PM_LABEL_INDOM.

       mmv_stats_add_metric_label adds a PM_LABEL_ITEM.

       mmv_stats_add_instance_label adds a PM_LABEL_INSTANCES.

RETURN VALUES         top

        When adding metrics, indoms, instances and labels, if correct
       returns 0
        and if not it returns an errno code. The other 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         top

       mmv_inc_value(3), mmv_lookup_value_desc(3), strerror(3) and

COLOPHON         top

       This page is part of the PCP (Performance Co-Pilot) project.
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       ⟨⟩ on 2023-12-22.
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Performance Co-Pilot                               MMV_STATS_REGISTRY(3)

Pages that refer to this page: mmv_stats_init(3)pmdiscoversetup(3)pmsearchsetup(3)pmseriessetup(3)pmwebtimerregister(3)mmv(5)