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)

2 files changed, 20 insertions, 1 deletions

diff --git a/ctdb/include/ctdb.h b/ctdb/include/ctdb.h
index abe09a3f96..1ede66205a 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;
 
diff --git a/ctdb/include/ctdb_private.h b/ctdb/include/ctdb_private.h
index 2f4937e60f..ad84628a99 100644
--- a/ctdb/include/ctdb_private.h
+++ b/ctdb/include/ctdb_private.h
@@ -160,7 +160,6 @@ typedef void (*ctdb_control_callback_fn_t)(struct ctdb_context *,
 					   int32_t status, TDB_DATA data, 
 					   const char *errormsg,
 					   void *private_data);
-
 /*
   structure describing a connected client in the daemon
  */
@@ -173,6 +172,7 @@ struct ctdb_client {
 	struct ctdb_tcp_list *tcp_list;
 	uint32_t db_id;
 	uint32_t num_persistent_updates;
+	struct ctdb_client_notify_list *notify;
 };
 
 
@@ -612,6 +612,8 @@ enum ctdb_controls {CTDB_CONTROL_PROCESS_EXISTS          = 0,
 		    CTDB_CONTROL_SET_DB_PRIORITY         = 111,
 		    CTDB_CONTROL_GET_DB_PRIORITY         = 112,
 		    CTDB_CONTROL_TRANSACTION_CANCEL      = 113,
+		    CTDB_CONTROL_REGISTER_NOTIFY         = 114,
+		    CTDB_CONTROL_DEREGISTER_NOTIFY       = 115,
 };	
 
 /*
@@ -1501,4 +1503,8 @@ int32_t ctdb_control_set_ban_state(struct ctdb_context *ctdb, TDB_DATA indata);
 int32_t ctdb_control_get_ban_state(struct ctdb_context *ctdb, TDB_DATA *outdata);
 int32_t ctdb_control_set_db_priority(struct ctdb_context *ctdb, TDB_DATA indata);
 
+int32_t ctdb_control_register_notify(struct ctdb_context *ctdb, uint32_t client_id, TDB_DATA indata);
+
+int32_t ctdb_control_deregister_notify(struct ctdb_context *ctdb, uint32_t client_id, TDB_DATA indata);
+
 #endif