votequorum_initialize - Create a new connection to the VoteQuorum service
#include <corosync/votequorum.h>
int votequorum_initialize(votequorum_handle_t *handle,
votequorum_callbacks_t *callbacks);
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.
This call returns the CS_OK value if successful, otherwise an error is returned.
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
votequorum_overview(3),
votequorum_finalize(3),
votequorum_getinfo(3),
votequorum_trackstart(3),
votequorum_trackstop(3),
votequorum_fd_get(3),
votequorum_dispatch(3),
votequorum_context_set(3),
votequorum_context_get(3),
votequorum_setexpected(3),
votequorum_setvotes(3)