Tribblix: manual page: cmap_track

CMAP_TRACK_ADD(3) Corosync Cluster Engine Programmer's Manual

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.

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

SEE ALSO