NAME | C SYNOPSIS | DESCRIPTION | ADD METRICS | ADD INDOMS | ADD INSTANCES | ADD LABELS | RETURN VALUES | SEE ALSO | COLOPHON

MMV_STATS_REGISTRY(3)     Library Functions Manual     MMV_STATS_REGISTRY(3)

NAME         top

       mmv_stats_registry - 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_inc_value(3).

       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 automatically.

       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 error.

       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 *value,
                                        mmv_value_type_t type, int
       optional);

       int mmv_stats_add_indom_label(mmv_registry_t *registry, int serial,
                                     const char *name, const char *value,
                                     mmv_value_type_t type, int optional);

       int mmv_stats_add_metric_label(mmv_registry_t *registry, int item,
                                      const char *name, const char *value,
                                      mmv_value_type_t type, int optional);

       int mmv_stats_add_instance_label(mmv_registry_t *registry, int
               serial,
                                        int instid, const char *name, const
               char *value,
                                        mmv_value_type_t type, int
               optional);

       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,
       MMV_NUMBER_TYPE, MMV_BOOLEAN_TYPE, MMV_NULL_TYPE, MMV_ARRAY_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
       PM_LABEL_OPTIONAL.

       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 mmv(5).

COLOPHON         top

       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
       2019-07-28.  (At that time, the date of the most recent commit that
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       (which is not part of the original manual page), send a mail to
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Performance Co-Pilot                                   MMV_STATS_REGISTRY(3)

Pages that refer to this page: mmv_stats_init(3)