cmap_track_add(3)

1CMAP_TRACK_ADD(3) Corosync Cluster Engine Programmer's ManualCMAP_TRACK_ADD(3)
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NAME

6       cmap_track_add - Set tracking function for values in CMAP
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SYNOPSIS

10       #include <corosync/cmap.h>
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13       cs_error_t  cmap_track_add (cmap_handle_t handle, const char *key_name,
14       int32_t  track_type,  cmap_notify_fn_t  notify_fn,   void   *user_data,
15       cmap_track_handle_t *cmap_track_handle);
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DESCRIPTION

19       The  cmap_track_add  function  is  used  to  set  function which tracks
20       changes in CMAP. One CMAP connection can track multiple keys  and  also
21       it's  possible  to track one key multiple times. The handle argument is
22       connection to CMAP  database  obtained  by  calling  cmap_initialize(3)
23       function.   key_name  argument is ether exact key name or prefix of key
24       name to track changes on.  track_type is bitfield which may consist  of
25       following values:
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27       CMAP_TRACK_ADD - track addition of new key (or key added in callback)
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29       CMAP_TRACK_DELETE - track deletion of key (or key deleted in callback)
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31       CMAP_TRACK_MODIFY - track modification of key (or key modified in call‐
32       back)
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34       CMAP_TRACK_PREFIX - whole prefix is tracked, instead of  key  only,  so
35       "totem."  tracking  means  that  "totem.nodeid",  "totem.version",  ...
36       applies (this value is never returned in callback)
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38       notify_fn is pointer to function which is called when value is changed.
39       It's   definition   and  meaning  of  parameters  is  discussed  below.
40       user_data argument is passed directly to notify_fn without any changes.
41       cmap_track_handle  is  used  for  removing  of  tracking when no longer
42       needed by calling cmap_track_delete(3) function.
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44       Callback function is defined as:
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46              typedef void (*cmap_notify_fn_t) (
47                  cmap_handle_t cmap_handle,
48                  cmap_track_handle_t cmap_track_handle,
49                  int32_t event,
50                  const char *key_name,
51                  struct cmap_notify_value new_value,
52                  struct cmap_notify_value old_value,
53                  void *user_data);
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55       where cmap_handle is handle used in  registration  of  track  function.
56       cmap_track_handle is handle returned by cmap_track_add function.  event
57       is  one  of  CMAP_TRACK_ADD,  CMAP_TRACK_DELETE  or  CMAP_TRACK_MODIFY.
58       key_name  is  name  of  changed key.  new_value is new value of key, or
59       unset if event is CMAP_TRACK_DELETE.  old_value is  previous  value  of
60       key  or  unset  if event is CMAP_TRACK_ADD or for some special keys set
61       directly by Corosync due to speed optimizations.   Both  new_value  and
62       old_value are structures defined as:
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64              struct cmap_notify_value {
65                  cmap_value_types_t type;
66                  size_t len;
67                  const void *data;
68              };
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70       If  value  is  unset, all fields are set to 0. Otherwise type is one of
71       cmap types (as described in cmap_get(3) function),  len  is  length  of
72       value  in  cmap  and  data is pointer to value of item. Data storage is
73       dynamically allocated by caller and notify function  must  not  try  to
74       free it.
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RETURN VALUE

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

SYNOPSIS

DESCRIPTION

RETURN VALUE

SEE ALSO