-
heartbeat
-
EstablishConnection: only create, save connection refs on init. cannot concurrently write to map -
client session (*)
- session id
- heartbeat timeout for session expiry
-
watch event (*)
- Since data changes must be approved by quorum/leader, data watches can be set globally and maintained locally at each server.
- when event fires, server clears the watch and notifies if the corresponding client is connected
- watch event must be sent to client and response given before any other commands are processed for that client
- Children changes are similar, but we maintain a separate list.
- create(watch=true) => set child and data watch
- getChildren(watch=true) => set child watch
- getData(watch=true) and exists(watch=true) => set data watch
- setData(watch=true) => trigger data watch
- delete(path) => trigger data watch and child watch for path and child watch for its parent
-
leader election protocol (*)
- leader timeout
- send out leader events
-
parent counter for sequential nodes
- monotonically increasing
-
leader approved events
- zxid
- version numbers
- ticks
- realtime
- zookeeper stat structure?
-
znode data
- sanity checks to ensure size is less than 1MB
- size should be at most 1MB but usually much smaller
-
ephemeral nodes (+)
- delete on session expiry
-
sequential nodes (*)
-
client permissions (+)
- read
- write
- create
- delete
- admin
-
dynamic configuration (++)