QUORUM_MODEL_INITIALIZE(3)

NAME
quorum_model_initialize - Create a new connection to the Quorum service

SYNOPSIS
#include <corosync/quorum.h>

cs_error_t quorum_model_initialize(quorum_handle_t *handle, quorum_model_t model, quorum_model_data_t *model_data, uint32_t *quorum_type,void *context);

DESCRIPTION
The quorum_model_initialize function is an enhanced way to initialize a connection to the quorum API.

Each application may have several connections to the quorum API. Each application uses the handle argument to uniquely identify the connection. The handle argument is then used in other function calls to identify the connection to be used for communication with the quorum service.

The model is used to explicitly choose set of callbacks and internal parameters. Currently two models QUORUM_MODEL_V0 and QUORUM_MODEL_V1 are defined. QUORUM_MODEL_V0 exists only for compatibility reasons with quorum_initialize(3) function and it is not recommended to be used as an argument for quorum_model_initialize(3).

The Following description is focused only on QUORUM_MODEL_V1 model.

Every time the voting configuration changes (eg a node joins or leave the cluster) or the quorum status changes the quorum callback is called. The quorum callback function is described by the following type definitions:

typedef void (*quorum_v1_quorum_notification_fn_t) (
        quorum_handle_t handle,
        uint32_t quorate,
        struct quorum_ring_id ring_id,
        uint32_t member_list_entries,
        const uint32_t *member_list
);

Also every time when membership configuration changes (eg a node joins or leave the cluster) the node list change callback is called before the quorum callback. The node list change callback function is described by the following type definitions:

typedef void (*quorum_v1_nodelist_notification_fn_t) (
        quorum_handle_t handle,
        struct quorum_ring_id ring_id,
        uint32_t member_list_entries,
        const uint32_t *member_list,
        uint32_t joined_list_entries,
        const uint32_t *joined_list,
        uint32_t left_list_entries,
        const uint32_t *left_list
);

The model_data argument for QUORUM_MODEL_V1 is of the type:

typedef struct {
        quorum_model_t model;
        quorum_v1_quorum_notification_fn_t quorum_notify_fn;
        quorum_v1_nodelist_notification_fn_t nodelist_notify_fn;
} quorum_model_v1_data_t;

It's not required (nor recommended) to set model field in the structure. It is also fine if only some of notification callbacks are used (only these events will be delivered then).

The quorum_type argument is set to:

#define QUORUM_FREE     0
#define QUORUM_SET      1

QUORUM_FREE value means that no quorum algorithm is loaded and that no callbacks will take place.

QUORUM_SET value means that one quorum algorithm is configured and that callbacks will take place.

The context argument sets context same way as quorum_context_set(3).

When a configuration change occurs, the callback is called from the quorum_dispatch(3) function.

RETURN VALUE
This call returns the CS_OK value if successful, otherwise an error is returned.

ERRORS

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

SEE ALSO
quorum_overview(3), quorum_initialize(3), quorum_finalize(3), quorum_getquorate(3), quorum_trackstart(3), quorum_trackstop(3), quorum_fd_get(3), quorum_dispatch(3), quorum_context_set(3), quorum_context_get(3)