They merely syncs brand new texts delivered shortly after a separate WebSocket connection is established
Sub-problem 4: Ultimate Consistency
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Reproductions could become out-of-sync with each other in collaborative editing tutorial but we need make sure that the newest claims kept in the imitation usually at some point converge.
- From the t = T0 , Alice goes off-line
- In the t = T1 , Alice attempted to posting an emails M1 (publish fails)
- At the t = T2 , Bob directs M2
- At the t = T3 , Alice goes online once more. WebSocket is re-depending
- During the t = T4 , Alice sends M4
- During the t = T5 , Bob upload M5
- At t = T6 , Alice re also-directs M1
M4 M5 M1
M2 M4 M5 M1
Exactly what Bob sees was in line with just what machine observes from the T6 but there is good divergence (inconsistency) between Alice's chat history and you can Bob's cam record. For the reason that whenever Alice comes back on the web within T3 , Alice's customer does not down load another duplicate of the cam history throughout the host.
We steer clear of the need certainly to resolve the brand new disagreement resolution condition from the staying the consumer version following system relationship is done once again and never pressuring that it is consistent with the server variation. Due to the fact there isn't any polling, the sole machine-driven revise for the consumer imitation is actually from WebSocket situations.
The latest OkCupid chat app lets you go off-line getting a random amount of time and you can keep delivering brand new messages. not, if you are online once again, it generally does not automatically obtain every texts provided for your when you had been off-line and you will lso are-pertain their off-line edits in addition newest state.
Going for the ideal last state when concurrent updates have took place is actually named reconciliation and can feel somewhat tricky to apply.
As an instance, there is certainly a disadvantage to only syncing this new reproductions towards server condition in the event the system has reached regular-state: It will violate the newest invariant for our collection wherein messages is actually usually bought by the time they certainly were created.