bionic (3) cmap_track_add.3.gz

NAME

       cmap_track_add - Set tracking function for values in CMAP

SYNOPSIS

       #include <corosync/cmap.h>

       cs_error_t   cmap_track_add   (cmap_handle_t   handle,   const   char   *key_name,   int32_t  track_type,
       cmap_notify_fn_t notify_fn, void *user_data, cmap_track_handle_t *cmap_track_handle);

DESCRIPTION

       The cmap_track_add function is used to set function which tracks changes in CMAP. One CMAP connection can
       track  multiple  keys  and  also  it's  possible  to track one key multiple times. The handle argument is
       connection to CMAP database obtained by calling cmap_initialize(3) function.  key_name argument is  ether
       exact  key  name  or prefix of key name to track changes on.  track_type is bitfield which may consist of
       following values:

       CMAP_TRACK_ADD - track addition of new key (or key added in callback)

       CMAP_TRACK_DELETE - track deletion of key (or key deleted in callback)

       CMAP_TRACK_MODIFY - track modification of key (or key modified in callback)

       CMAP_TRACK_PREFIX - whole prefix is tracked, instead  of  key  only,  so  "totem."  tracking  means  that
       "totem.nodeid", "totem.version", ... applies (this value is never returned in callback)

       notify_fn  is  pointer  to function which is called when value is changed. It's definition and meaning of
       parameters is discussed below.  user_data argument is passed directly to notify_fn without  any  changes.
       cmap_track_handle  is used for removing of tracking when no longer needed by calling cmap_track_delete(3)
       function.

       Callback function is defined as:

              typedef void (*cmap_notify_fn_t) (
                  cmap_handle_t cmap_handle,
                  cmap_track_handle_t cmap_track_handle,
                  int32_t event,
                  const char *key_name,
                  struct cmap_notify_value new_value,
                  struct cmap_notify_value old_value,
                  void *user_data);

       where cmap_handle is handle used in registration of track function.  cmap_track_handle is handle returned
       by  cmap_track_add  function.   event  is  one of CMAP_TRACK_ADD, CMAP_TRACK_DELETE or CMAP_TRACK_MODIFY.
       key_name is name of changed key.  new_value is new value of key, or unset if event is  CMAP_TRACK_DELETE.
       old_value  is  previous  value  of  key  or unset if event is CMAP_TRACK_ADD or for some special keys set
       directly by Corosync due to speed optimizations.  Both new_value and old_value are structures defined as:

              struct cmap_notify_value {
                  cmap_value_types_t type;
                  size_t len;
                  const void *data;
              };

       If value is unset, all fields are set to 0. Otherwise  type  is  one  of  cmap  types  (as  described  in
       cmap_get(3)  function), len is length of value in cmap and data is pointer to value of item. Data storage
       is dynamically allocated by caller and notify function must not try to free it.

RETURN VALUE

       This call returns the CS_OK value if successful. It can return CS_ERR_INVALID_PARAM if notify_fn is  NULL
       or track_type is invalid value.

SEE ALSO

       cmap_track_delete(3), cmap_initialize(3), cmap_get(3), cmap_dispatch(3), cmap_overview(8)

       CS_ERR_TRY_AGAIN Resource temporarily unavailable

       CS_ERR_INVALID_PARAM Invalid argument

       CS_ERR_ACCESS Permission denied

       CS_ERR_LIBRARY The connection failed

       CS_ERR_INTERRUPT System call interrupted by a signal

       CS_ERR_NOT_SUPPORTED The requested protocol/functionality not supported

       CS_ERR_MESSAGE_ERROR Incorrect auth message received

       CS_ERR_NO_MEMORY Not enough memory to complete the requested task