Messages

T_ACK

T_ACK message is sent from server to the client.
T_ACK message is to reply the request message.
The fields will depend on the request.

T_INIT

It is used to exchange the parameters with the quorum server.

When

When client (quorum plugin) connects to quorum server, the first message is T_INIT.

Fields

cl_name : the name of the cluster which the client belong to
t_timeout : the timeout value of the client
t_giveup : how long will take for the client to give up all it's resources
client_id : (optional) the id of the client

Server Actions

add a new client to the cluster named with cl_name. if there is a client_id field, use the existing client with the same id
reply the message with the timeout of cluster
start a remove-client timer with the value of client's timeout, the action of the timer is to remove the client

Expect Reply

result : "fail" or "ok"
timeout : the timeout value of the server
client_id : the id of the client

Client Actions

record the timeout of cluster, and the client_id
start a periodic timer to send T_QUORUM message to server

T_QUORUM

It is used to get the the quorum information from the quorum server. And same time, it's a kind of heartbeat to tell the server that the client is alive.

When

A periodic timer will invoke the sending of T_QUORUM message after T_INIT message successed.

Fields

None

Server Actions

calculate the quorum of the cluster
if the quorum is not changed, reply the quorum to the client
if the quorum changed, change to wait_for_change status. the status will last for timeout+giveup of the client which takes the quorum. during this period, all T_QUORUOM message will be replied with NO_QUORUM.
restart the remove-client timer for the client.

Expect Reply

result : "fail" or "ok"
quorum : 0 or 1

Client Actions

store the quorum status

T_BRB

Tell the quorum server that current connection will be broken but will come back soon.

When

When the leader of the partation will change soon.

Fields

t_brb : how long will take for the client to change the leader (when the connect broken, the client data will be remained for t_changeleader)