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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

1. 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
2. reply the message with the timeout of cluster
3. 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

1. record the timeout of cluster, and the client_id
2. 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

1. calculate the quorum of the cluster
2. if the quorum is not changed, reply the quorum to the client
3. 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.
4. restart the remove-client timer for the client.

Expect Reply

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

Client Actions

1. 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)

Server Actions

1. set the brb timeout value to the client.
2. when the client disconnects, the data will be keeped for brb timeout.

Expect Reply

• result : "fail" or "ok"

Client Actions

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