Maintenance and Discontinuation

The Two Announcements Compared

There are two announcements for planned unavailability, differing in their duration and in how final they are.

Announcing a Maintenance Window

A maintenance window is announced in the Setup GTNet view. Select your own server entry — or no row at all — and choose “Send GT Net Message” from the context menu. The message type “Server is in maintenance mode during time period” is available there. The two fields “Start” and “End” have to be filled in; both must lie in the future and “End” must be after “Start”.

Several maintenance windows may be announced at the same time, as long as they do not overlap. A window that reaches into an already announced one is rejected with an error message. This allows a series of recurring maintenance evenings to be published in advance, for example.

The announcement changes nothing on your own instance. It is purely information for the peers; your own server keeps running unchanged until the maintenance actually begins and has to be shut down at the announced time by yourself.

What Happens During a Maintenance Window

The recipient stores the announced window and evaluates it as soon as it begins. Between “Start” and “End” the instance in question is asked neither for intraday prices nor for historical prices or security metadata, and no messages are sent to it either. The online status check also leaves the instance untouched during this period, so that a planned shutdown is not incorrectly recorded as “Offline”.

After “End” the instance is used entirely normally again. No intervention is required and no all-clear has to be sent; the window expires by itself.

Which windows a peer has announced is shown in the server overview: the expanded row contains the “Maintenance windows” area with the “Start” and “End” of every reported window. Windows that have already expired remain visible there until the corresponding message is deleted.

Announcing the Discontinuation

If an instance is being shut down permanently, this is announced with the message “Server operation will be discontinued as of this date”. The field “Discontinued as of” has to be filled in and must lie in the future. Only one discontinuation can be open at a time; while one is announced, the message type is no longer offered for selection.

Until the announced date everything stays unchanged: the peers continue to use the instance as a data supplier and send messages to it. The advance notice therefore costs no data exchange, it gives the peers time to look for other sources.

What Happens From the Announced Date

From the date “Discontinued as of” the recipient sets the “Server Online” column of the instance in question to “Out of service”. At the same time all information objects of that instance receive the “Status Server” “Closed” and “Accept request” “Closed”, which drops the instance out of supplier selection.

This state is final. Neither an online status check nor an incoming message from the instance in question lifts it again — not even if the server unexpectedly keeps answering. This prevents a discontinued instance from being silently put back into service by an accidentally successful ping.

The switch is performed by a background task that runs every five hours. It is therefore not made to the minute, but within a few hours of the announced date.

stateDiagram-v2
    [*] --> Unknown
    Unknown --> Online: Ping successful
    Online --> Offline: Ping failed
    Offline --> Online: Ping successful
    Online --> OutOfService: Announced date reached
    Offline --> OutOfService: Announced date reached
    OutOfService --> Unknown: Operation discontinuation cancelled

    state OutOfService: Out of service

    note right of OutOfService : Lifted neither by a status check nor by a message

After the discontinuation the entry can be deleted from the context menu of the server overview. Its messages, exchange settings and exchange logs disappear with it. If you would rather keep the instance, for instance because it may go back into operation after all, set “Server Online” to a different value by hand in the edit dialog.

Revoking an Announcement

Both announcements can be withdrawn. Select the sent announcement in the message list of your own entry and choose “Reverse” from the context menu. This sends “Maintenance cancelled” or “Operation discontinuation cancelled” to all peers; they then discard the maintenance window or the pending discontinuation.

The menu entry only appears while the announced moment still lies in the future: for a maintenance window before its “Start”, for a discontinuation before the date “Discontinued as of”. A maintenance window that is already running is not ended prematurely, it expires with “End”.

Delivery of the Announcements

Announcements go to all peers with which a data exchange has been set up and the handshake completed. They are delivered immediately after being sent; if a peer is unreachable at that moment, a background task repeats the delivery later. A peer whose handshake is only established after the announcement still receives it, provided it is still valid at that point.