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86d1b4c465
The way to use this is from a client to :
1, first create a message handle and bind it to a SRVID
A special prefix for the srvid space has been set aside for samba :
Only samba is allowed to use srvid's with the top 32 bits set like this.
The lower 32 bits are for samba to use internally.
2, register a "notification" using the new control :
CTDB_CONTROL_REGISTER_NOTIFY = 114,
This control takes as indata a structure like this :
struct ctdb_client_notify_register {
uint64_t srvid;
uint32_t len;
uint8_t notify_data[1];
};
srvid is the srvid used in the space set aside above.
len and notify_data is an arbitrary blob.
When notifications are later sent out to all clients, this is the payload of that notification message.
If a client has registered with control 114 and then disconnects from ctdbd, ctdbd will broadcast a message to that srvid to all nodes/listeners in the cluster.
A client can resister itself with as many different srvid's it want, but this is handled through a linked list from the client structure so it mainly designed for "few notifications per client".
3, a client that no longer wants to have a notification set up can deregister using control
CTDB_CONTROL_DEREGISTER_NOTIFY = 115,
which takes this as arguments :
struct ctdb_client_notify_deregister {
uint64_t srvid;
};
When a client deregisters, there will no longer be sent a message to all other clients when this client disconnects from ctdbd.
(This used to be ctdb commit f1b6ee4a55cdca60f93d992f0431d91bf301af2c)