corosync/man/cmap_track_add.3.in

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.TH "CMAP_TRACK_ADD" 3 "06/02/2012" "corosync Man Page" "Corosync Cluster Engine Programmer's Manual"

.SH NAME
.P
cmap_track_add \- Set tracking function for values in CMAP

.SH SYNOPSIS
.P
\fB#include <corosync/cmap.h>\fR

.P
\fBcs_error_t
cmap_track_add (cmap_handle_t \fIhandle\fB, const char *\fIkey_name\fB, int32_t \fItrack_type\fB,
cmap_notify_fn_t \fInotify_fn\fB, void *\fIuser_data\fB, cmap_track_handle_t *\fIcmap_track_handle\fB);\fR

.SH DESCRIPTION
.P
The
.B 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
.I handle
argument is connection to CMAP database obtained by calling
.B cmap_initialize(3)
function.
.I key_name
argument is ether exact key name or prefix of key name to track changes on.
.I track_type
is bitfield which may consist of following values:
.PP
\fBCMAP_TRACK_ADD\fR - track addition of new key (or key added in callback)
.PP
\fBCMAP_TRACK_DELETE\fR - track deletion of key (or key deleted in callback)
.PP
\fBCMAP_TRACK_MODIFY\fR - track modification of key (or key modified in callback)
.PP
\fBCMAP_TRACK_PREFIX\fR - 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)
.PP
.I notify_fn
is pointer to function which is called when value is changed. It's definition and meaning of parameters
is discussed below.
.I user_data
argument is passed directly to
.I notify_fn
without any changes.
.I cmap_track_handle
is used for removing of tracking when no longer needed by calling
.B cmap_track_delete(3)
function.

Callback function is defined as:
.IP
.RS
.ne 18
.nf
.PP
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);
.ta
.fi
.RE
.IP
.PP
where
.I cmap_handle
is handle used in registration of track function.
.I cmap_track_handle
is handle returned by
.B cmap_track_add
function.
.I event
is one of \fBCMAP_TRACK_ADD\fR, \fBCMAP_TRACK_DELETE\fR or \fBCMAP_TRACK_MODIFY\fR.
.I key_name
is name of changed key.
.I new_value
is new value of key, or unset if
.I event
is \fBCMAP_TRACK_DELETE\fR.
.I old_value
is previous value of key or unset if
.I event
is \fBCMAP_TRACK_ADD\fR or for some special keys set directly by Corosync due to speed optimizations.
Both
.I new_value
and
.I old_value
are structures defined as:
.IP
.RS
.ne 18
.nf
.PP
struct cmap_notify_value {
    cmap_value_types_t type;
    size_t len;
    const void *data;
};
.ta
.fi
.RE
.IP
.PP
If value is unset, all fields are set to 0. Otherwise
.I type
is one of cmap types (as described in
.B cmap_get(3)
function),
.I len
is length of value in cmap and
.I data
is pointer to value of item. Data storage is dynamically allocated by caller and notify function must not try to
free it.

.SH 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.

.SH NOTES
Modification tracking of individual keys is supported in the stats map, but not
prefixes. Add/Delete operations are supported on prefixes though so you can track
for new ipc connections or knet interfaces.
In the icmap map, prefix tracking is fully supported.

.SH "SEE ALSO"
.BR cmap_track_delete (3),
.BR cmap_initialize (3),
.BR cmap_get (3),
.BR cmap_dispatch (3),
.BR cmap_overview (3)