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.TH CPG_MODEL_INITIALIZE 3 2024-07-15 "corosync Man Page" "Corosync Cluster Engine Programmer's Manual"
.SH NAME
cpg_model_initialize \- Create a new connection to the CPG service
.SH SYNOPSIS
.B #include <corosync/cpg.h>
.sp
.BI "cs_error_t cpg_model_initialize(cpg_handle_t *" handle ", cpg_model_t " model ", cpg_model_data_t *" model_data ", void *" context ");

.SH DESCRIPTION
The
.B cpg_model_initialize
function is used to initialize a connection to the closed process groups API.
.PP
Each application may have several connections to the CPG API.  Each application
uses the
.I handle
argument to uniquely identify the connection.  The
.I handle
argument is then used in other function calls to identify the connection to be used
for communication with the CPG service.
.PP
Argument
.I model
is used to explicitly choose set of callbacks and internal parameters. Currently only model
.I CPG_MODEL_V1
is defined.
.PP
Callbacks and internal parameters are passed by
.I model_data
argument. This is casted pointer (idea is similar as in sockaddr function) to one of structures
corresponding to chosen model. Currently only
.I cpg_model_v1_data_t
is needed.
.SH MODEL_V1
The
.I MODEL_V1
is backwards compatible with original callbacks initialized by
.I cpg_initialize
but new callback
.I cpg_totem_confchg_fn
is defined.
.PP
Every time an CPG event occurs within the joined group, one of the callbacks specified by the argument
.I callbacks
is called.  The callback functions are described by the following type definitions:
.PP
.PP
.IP
.RS
.ne 18
.nf
.ta 4n 20n 32n

typedef void (*cpg_deliver_fn_t) (
        cpg_handle_t handle,
        const struct cpg_name *group_name,
        uint32_t nodeid,
        uint32_t pid,
        const void *msg,
        size_t msg_len);


typedef void (*cpg_confchg_fn_t) (
        cpg_handle_t handle,
        const struct cpg_name *group_name,
        const struct cpg_address *member_list, size_t member_list_entries,
        const struct cpg_address *left_list, size_t left_list_entries,
        const struct cpg_address *joined_list, size_t joined_list_entries);


typedef void (*cpg_totem_confchg_fn_t) (
        cpg_handle_t handle,
        struct cpg_ring_id ring_id,
        uint32_t member_list_entries,
        const uint32_t *member_list);
.ta
.fi
.RE
.IP
.PP
.PP
The
.I cpg_model_v1_data_t
structure is defined as:
.IP
.RS
.ne 18
.nf
.PP
typedef struct {
        cpg_model_t model;
        cpg_deliver_fn_t cpg_deliver_fn;
        cpg_confchg_fn_t cpg_confchg_fn;
        cpg_totem_confchg_fn_t cpg_totem_confchg_fn;
        unsigned int flags;
} cpg_model_v1_data_t;
.ta
.fi
.RE
.IP
.PP
When a configuration change occurs or a message is to be delivered one of the callbacks
is called from the
.B cpg_dispatch()
function.  If a configuration change occurs,
.I cpg_confchg_fn
is called.  If a delivery of a message occurs,
.I cpg_deliver_fn
is called.
When totem membership change occurs,
.I cpg_totem_confchg_fn
is called. You can OR
.I CPG_MODEL_V1_DELIVER_INITIAL_TOTEM_CONF
constant to flags to get callback after first confchg event.

The
.I cpg_address
structure is defined
.IP
.RS
.ne 18
.nf
.PP
struct cpg_address {
        unsigned int nodeid;
        unsigned int pid;
        unsigned int reason;
};
.ta
.fi
.RE
.IP
.PP
where nodeid is a 32 bit unique node identifier, pid is the process ID of the process that has joined/left the group
or sent the message, and reason is an integer code indicating why the node joined/left the group (this value is not
set for the member_list items).
.PP
.IP
.RS
.ne 18
.nf
.PP
CPG_REASON_JOIN      - the process joined a group using cpg_join().
CPG_REASON_LEAVE     - the process left a group using cpg_leave()
CPG_REASON_NODEDOWN  - the process left a group because the node left the cluster.
CPG_REASON_NODEUP    - the process joined a group because it was already a member of a group on a node that has just joined the cluster
CPG_REASON_PROCDOWN  - the process left a group without calling cpg_leave()
CPG_REASON_UNDEFINED - a special value used for the member_list items
.ta
.fi
.RE
.IP
.PP
The
.I cpg_ring_id
structure is defined
.IP
.RS
.ne 18
.nf
.PP
struct cpg_ring_id {
        uint32_t nodeid;
        uint64_t seq;
};
.ta
.fi
.RE
.IP
.PP
where
.I nodeid
is the current Totem leader and
.I seq
is an increasing number.

.PP
.SH RETURN VALUE
This call returns the CS_OK value if successful, otherwise an error is returned.
.PP
.SH ERRORS
The errors are undocumented.
.SH "SEE ALSO"
.BR cpg_overview (3),
.BR cpg_initialize (3),
.BR cpg_finalize (3),
.BR cpg_fd_get (3),
.BR cpg_dispatch (3),
.BR cpg_join (3),
.BR cpg_leave (3),
.BR cpg_mcast_joined (3),
.BR cpg_membership_get (3)
.BR cpg_zcb_alloc (3)
.BR cpg_zcb_free (3)
.BR cpg_zcb_mcast_joined (3)
.BR cpg_context_get (3)
.BR cpg_context_set (3)
.BR cpg_local_get (3)
.BR cpg_model_initialize (3)

.PP
