CRDB is Redislabs - Geo-Replicated, (Strong) Eventually Consistent CRDTs based Redis. This presentation was give as part of RedisConf 2017 San Fransisco.

1. Multi-Master Geo Distributed Redis
With Redis Enterprise (Redise)
Elad Ash

2. Challenge and requirements
The solution in a nutshell
Redis data types examples
Status and availability
What we’ll cover

3. challenge and requirements

4. Use Cases - multi-master multi-region REDIS
• Geo Distributed Trading/Bidding
- Auctions, Bids/Asks
Lists/Sorted Sets tracking Bids and Asks
• Dashboards & Scoreboards
- Tracking Geo Distributed Scoreboards
Sorted Sets tracking ordered scores
• Real-time session management and
Metering Apps
- HA for session management
- Tracking Usage/Consumption
- A/B testing
Hashes/Sets/Lists/Expiry Tracking Consumption Events
• Fraud Detection
- Geo Distributed Event Tracking
Sets Gathering Geo Distributed Events
• Social Engagement Apps
- Encoding Social Engagement
Distributed Counters for “Likes”, “Shares”, “Retweets”
• Collaboration Apps
- Constructing Smart Timelines
Merged Lists Ordering Posts
- Instant Messaging & Conversation Tracking
Merged Lists Ordering Conversations

5. The 3 base requirements
1.Scale the same data set globally
2.Redis speed
3.No change to application

6. App
Scaling multi region redis challenge - Consensus?
Redis is fast: > 1,000,000 ops/sec, < 1 mSec
latency
Network east-west RTT is even slower > 70 mSec
Consensus requires clusters coordination which is
too slow for Redis
LWW by itself, can't solve Redis complex data-
type conflicts

7. The solution in a nutshell
Redislabs CRDB
Geo-Replicated
(Strong) Eventually Consistent
CRDTs based Redis
Conflict free Resolved DataBase | Cross Region DataBase | Cluster Replicated DataBase

8. Redis Replication
Been there forever...
Master -> Slave(s) model
Slave may be a master for other slaves
Constructed for High Availability (switch roles)

9. Redise replica-of for geo replication
DB1:
Read/Write replica
DB5:
Read replica
DB3:
Read replica
DB4:
Read replica
DB2:
Read replica

10. Redis Modules
● Since 4.0
● Dynamic libraries loaded to Redis
● With a C API
● Can extend Redis with:
New Capabilities
New Commands
New Data Types
10

11. CRDTs
Conflict Free Replicated Data Types (CRDTs)
• Years of academic research
• Based on consensus free protocol
• Strong eventual consistency
• Built to resolve conflicts with complex data
types
• Mostly transparent to users
Commutative
DAG
CmRDT

12. Reaching (Strong) Eventual Consistency with CRDT
1. Local ops: Reads & Writes locally
2. Async replication: Writes ops asynchronously replicated to all replicas
3. Consistency: CRDT model guarantees that the data-set would converge
to the same values, regardless of the order
Partial inconsistency - In any given time, the reads may yield different values,
but eventually (dependent on network latency) the values would converge
Simplify conflicts identifications - Maintain partial global ordering (identify
concurrent ops) = vector clocks

13. Vector Clocks for partial global ordering
A
B
C
{A=1,B=0,C=0}
{A=1,B=1,C=0}
{A=0}
{B=0}
{C=0}
{A=0,B=0,C=1} {A=0,B=0,C=2}
{A=1,B=2,C=0}
{A=0,B=0,C=3}
{A=1,B=3,C=3}
{A=2,B=3,C=3}

14. CRDB building blocks
Building block #1 - Redis Replication
Building block #2 - Redise Replica-Of for geo cluster replication
Building block #4 - Internal CRDT engine - strong eventual consistency
Building block #3 - Redis Modules

15. All together - CRDB: CRDT over Redise
Conflict free Resolved DataBase | Cross Region DataBase | Cluster Replicated DataBase
App
App App
CRDT
Module
CRDT
Module
CRDT
Module
1. Local read/writes
where clients use
regular redis commands
3. Bi-directional secured and
compressed async replica-of
a.k.a peer-replication
2. CRDTs implemented using
Redis Module

16. Demo
1. 1 geo distributed DB, replicated over 3 clusters
(replicas) on 3 regions: us-east, us-west, eu-west
2. Each Redise cluster generate load with
memtier_benchmark and a custom-built web-app.
3. To achieve Strong (without consensus protocol)
eventual consistency
● Operations are replicated between all replicas
(bi-directional and compressed)
● Use conflict free data types
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17. The benefits
Support different network topology
Support different cluster topologies as
well as scaling local DB as needed
RingFully-Connected
Performance is as fast as regular local redis
and enhanced globaly by replicas count

18. Data types examples

19. Example setup
App
AppReplica A Replica B
Two replicas, working over single data sets
Each step is done concurrently and then a synchronization takes
place
Then we present the reconciled value on both replica

20. COUNTERS

21. COUNTER: Creation
App
AppReplica A Replica B
> INCRBY mykey 10
(integer) 10
> GET mykey
(nil)
Syncing
Synced
> GET mykey
“10”
> GET mykey
“10”
> GET mykey
“10”

22. COUNTER: Multi-Value
App
AppReplica A Replica B
> INCRBY mykey 5
(integer) 15
> INCRBY mykey 8
(integer) 18
Syncing
Synced
> GET mykey
“23”
> GET mykey
“23”

23. COUNTER: Add wins / Observed remove
App
AppReplica A Replica B
> DEL mykey
(integer) 1
> DECRBY mykey 3
(integer) 20
Syncing
Synced
> GET mykey
(nil)
> GET mykey
“-3”
> GET mykey
“-3”

24. SETs

25. SET: Add wins / Observed remove
App
AppReplica A Replica B
> SADD myset X
(integer) 1
Syncing
Synced
> SMEMBERS myset
1) “X”
> SMEMBERS myset
1) “X”
> SMEMBERS myset
1) “X”
> SADD myset X
(integer) 1
> SREM myset X
(integer) 1
> SMEMBERS myset
(empty list or set)

26. SET: Add wins / Observed remove - another example
App
AppReplica A Replica B
Syncing
Synced
> SMEMBERS myset
1) “Y”
2) “X”
> SMEMBERS myset
1) “Y”
> SMEMBERS myset
1) “Y”
> DEL myset
(integer) 0
> SMEMBERS myset
(empty list or set)
> SADD myset Y
(integer) 1

27. REGISTERS (STRINGS)

28. STRINGS: Last Write Wins
App
AppReplica A Replica B
> SET mykey “A”
OK
Syncing
Synced
> GET mykey
“A”
> GET mykey
1) “B”
> GET mykey
1) “B”
> GET mykey
“B”
> SET mykey “B”
OK
Replica B write time is later the replica A

29. STRING: Add wins / Observed remove
App
AppReplica A Replica B
> DEL mykey
(integer)
> SET mykey “C”
OK
Syncing
Synced
> GET mykey
(nil)
> GET mykey
“C”
> GET mykey
“C”
> GET mykey
“C”

30. Status and Availability

31. Where will it be available

32. Status and
Availability
Preview state
1.Strings (Registers)
2.Counters
3.Sets
4.Pub-Sub
5.Expiry
6.Hashes
Preview in the next few month
Contact pm.group@redislabs.com
To enroll
GA with next version of RePack and
Re Cloud Private and
(2017)

33. Questions

34. Thank You
Elad Ash
VP R&D
Redislabs
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