Concept Name
Key word
Bloom Filter
Probabilistic existence of an element in a set
Consistent Hashing
Data Partition on Hashed ring; Virtual Nodes; Add/Delete Node easy
Quorum
Nr+Nw > N; Nw> N/2
Leader/Follower
Leaders only take R/W requests. Follower copies.
Write Ahead Log (WAL)
Log Write Requests in a Log before committing to DataStore
Segmented Logs
Logs files are splitted and rolled out to a central server
High Water Mark
Minimum updates with Quoram should be expose to client; On dead leader; next leader will have all updates under watermark.
Lease
Leasing out for some time; so client dies Lease is release. Better than taking exclusive lock.
Heartbeat
I am alive.
Gossip Protocol
Exchange what a node knows with a random set of nodes; eventually consistent.
Phi Accrual Failure
The probabilistic model for detecting failure; attach a probability with HeartBeat mechanism. Node is alive with 35% chances.
Split Brain
Old Leader is still alive; while new Leader is elected thinking that old was dead.
Fencing
Revoke access of Zombie Leader from critical resources like Log Server; that would not allow this server to act as Zombie Leader
Checksum
Ensure data integrity; add checksum to message
Vector Clocks
Global Clocks are not possible; GoogleGetTime()
CAP Theorem
In case pf Partition - Av Consistency
PACELC Theorem
If (Partition) {Av Con} E {La cons}
Hinted Handoff
Node (N) is down; then a coordinator node (C ) stores all write and when N comes back then all writes are forwarded to N.
Read Repair
While reading; send updates to outdated nodes.
Makale Tree
Minor differences in the data; take a Hash of segments. Most of them will end up matching the hash of segment.