What does it mean to be a
Real-Time Database?
bit.ly/meteor-rt-db
Meteor architecture
Optimistic UI
aka "Latency Compensation"
aka "client-side prediction"
"Dead reckoning" in gaming pathing
"speculative mutations"
Latency Compensation in Whatsapp
Latency Compensation in Hackpad
Learn about Optimistic UI
http://bit.ly/optimistic-ui
[demo of instagram.com]
User clicks a button =>
if (inSimulation) {
addMessage(
message: msg
isInFlight: true
...)
} else {
addMessage(message: msg ...)
}
Run RPC simulation =>
Run actual RPC =>
Display simulated changes =>
Propagate updates =>
"update"
Display actual changes =>
http://bit.ly/ddp-spec
MongoDB oplog
Timestamps!
Changes!
The RethinkDB integration
Works
- Queries
- Pub/sub
- RPCs
- Client-side cache
- Reqlite
- Client-side sim
Doesn't work
- Latency compensation
- Complex queries
- Filtering pub/sub
- Reqlite
Postgresql?
- Replication log == WAL
-
pg_current_xlog_location
-
pg_current_xlog_insert_location
Real-time database
- Can query
- Gives notifications with initial set
- Gives more metadata with revision numbers
- stores data
- doesn't lose data
- doesn't force you to write queries in Erlang
What does it mean to be a Real-Time Database?
By Slava Kim
