Add a mechanism where we can register notifications to be sent out to a SRVID when the client disconnects.

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)

1 files changed, 13 insertions, 0 deletions

diff --git a/ctdb/include/ctdb.h b/ctdb/include/ctdb.h
index abe09a3f966..1ede66205a2 100644
--- a/ctdb/include/ctdb.h
+++ b/ctdb/include/ctdb.h
@@ -111,6 +111,10 @@ struct ctdb_call_info {
 */
 #define CTDB_SRVID_TAKEOVER_RUN_RESPONSE  0xFD00000000000000LL
 
+/* A port reserved for samba (top 32 bits)
+ */
+#define CTDB_SRVID_SAMBA_NOTIFY  0xFE00000000000000LL
+
 /* used on the domain socket, send a pdu to the local daemon */
 #define CTDB_CURRENT_NODE     0xF0000001
 /* send a broadcast to all nodes in the cluster, active or not */
@@ -144,6 +148,15 @@ struct ctdb_client_control_state {
 	} async;	
 };
 
+struct ctdb_client_notify_register {
+	uint64_t srvid;
+	uint32_t len;
+	uint8_t notify_data[1];
+};
+
+struct ctdb_client_notify_deregister {
+	uint64_t srvid;
+};
 
 struct event_context;