Tribblix: manual page: votequorum

VOTEQUORUM_INITIALIZE(3) Corosync Cluster Engine Programmer's Manual

NAME

votequorum_initialize - Create a new connection to the VoteQuorum
service

SYNOPSIS

#include <corosync/votequorum.h>

int votequorum_initialize(votequorum_handle_t *handle,
votequorum_callbacks_t *callbacks);

DESCRIPTION

The votequorum_initialize function is used to initialize a connection
to the vote-based quorum database API.

Each application may have several connections to the votequorum 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
votequorum service.

Every time the voting configuration is about to change (eg a node
joins or leave the cluster), the callback is called. The callback
function is described by the following type definitions:

typedef void (*votequorum_nodelist_notification_fn_t) (
votequorum_handle_t handle,
uint64_t context,
uint32_t node_list_entries,
uint32_t node_list[]
);

Current ring_id (one get in votequorum_quorum_notification_fn) must
be passed to votequorum_qdevice_poll to make qdevice voting valid.

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

typedef void (*votequorum_quorum_notification_fn_t) (
votequorum_handle_t handle,
uint64_t context,
uint32_t quorate,
uint32_t node_list_entries,
votequorum_node_t node_list[]
);

The difference between votequorum_nodelist_notification_t and
votequorum_quorum_notification_t is subtle but important. The
'nodelist' callback is sent at the start of a cluster state
transition and contains the new ring_id and only the list of nodes
that are included in the sync state - ie only active nodes. No quorum
information is included this callback because it is not available at
that time. The 'quorum' callback is sent after the cluster state
transition has completed and does contain quorum information. In
addition, the nodelist contains a list of all nodes known to
votequorum (whether up or down) and their state as well as
information about the quorum device attached (if any). Quorum
callbacks will not be sent for qdevice up and down events unless they
affect quorum.

Every time the expected votes are changed, the callback is called.
The expected votes callback function is described by the following
type definitions:

typedef void (*votequorum_expectedvotes_notification_fn_t) (
votequorum_handle_t handle,
uint64_t context,
uint32_t expected_votes);

The callbacks argument is of the type:

typedef struct {
votequorum_quorum_notification_fn_t votequorum_quorum_notify_fn;
votequorum_expectedvotes_notification_fn_t votequorum_expectedvotes_notify_fn;
votequorum_nodelist_notification_fn_t votequorum_nodelist_notify_fn;
} votequorum_callbacks_t;

When a configuration change occurs, the callback is called from the
votequorum_dispatch() 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

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

SEE ALSO