Introduce Snapshot

[hackerwins]

Problem

Yorkie allows each client to exchange operations with the server. This causes a performance problem when a client attaches a document that has many accumulated operations.

Operations vs Snapshot in counter example:

• operation: (+1), (+1), (+1), (+1), (+1), (+1), (+1)
• snapshot: 7

Solution

The server stores snapshot at specific intervals then send a snapshot when the client attaches a document.

[hackerwins]

The response size of the attach API with 3972 changes is about 1.3 Mb in CodeMirror example.

[hackerwins]

without snapshot

The response size of the attach API with 4343 changes without a snapshot is about 2.5 Mb in Drawing example.

with snapshot

The response size of the attach API with 4250 changes with a snapshot is about 0.789 Mb in Drawing example.

[hackerwins]

I think that the payload will be reduced if we replace the size of actorID or perform garbage collection as follow-up work.

#3
#36

[hackerwins]

with snapshot + replace actor_id(24 bytes string -> 12 bytes array)

The response size of the attach API with 4296 changes with a snapshot is about 0.636 MB in Drawing example.

#36