This document provides an overview of Riak, a key-value database. It discusses that Riak uses buckets and bucket types to organize data, and supports common CRUD operations via its HTTP API. It also covers Riak's use of eventual consistency and quorums to balance availability and partition tolerance. Data types like sets and maps allow Riak to understand and resolve conflicts in the data.

1. RIAK 2.0
Engin Yöyen
October, 2014

2. What is Riak
• Key/Value Store
• hashTable[‘D018319’] = ‘Influenza’
• diseases = hashTable[‘D018319’]

3. Buckets
• There is no global namespace.
• All keys must belong to a bucket.
• diseases[‘D018319’] = ‘Influenza’
• symptoms[‘D018319’] = ‘cervical pains’

4. Why Bucket Types
• diseases[‘infectious’][‘D018319’] = ‘Influenza’
• diseases[‘blood-borne’][‘F023831’] = ‘Hepatitis B’
• Groups of buckets with a similar set of properties.
• diseases.props = {"search_index":"anyplace"}

5. The API

6. The API
via HTTP methods PUT, GET, POST, DELETE
Example
[hostAddress]/types/<type>/buckets/<bucket>/keys/<key>

7. PUT
curl -XPUT "http://localhost:8098/types/diseases/buckets/
infectious/keys/D018319"
-H "Content-Type:text/plain"
-d "Influenza, commonly known as, the flu, ...."
riak-admin bucket-type create diseases '{"props":
{"datatype":"set"}}'
riak-admin bucket-type activate diseases

8. PUT (2)
curl -v -XPUT "http://localhost:8098/types/diseases/buckets/
infectious/keys/D018319"
-H "Content-Type: application/json"
-d '{"desc": "Influenza, commonly known as, the flu, …."}'
Hint : http://localhost:8098/types/diseases/buckets/infectious/keys/D018319?returnbody=true

9. GET
http://localhost:8098/types/diseases/buckets/infectious/keys/
D018319

10. Post
http://localhost:8098/types/diseases/buckets/infectious/keys

11. Delete
I am sure you all figured out by now….

12. Hints

13. Hints - Buckets
http://localhost:8098/types/diseases/buckets?buckets=true
{
"buckets": [
"blood-borne",
"infectious"
]
}

14. Hints - Keys
http://localhost:8098/types/diseases/buckets/infectious/keys?keys=true
{
"keys": [
"Uhz73mNfxkEkcmFsLcgu3Kan5Dw",
"D018319",
"WapIL5eeRbnXkocmcK3YK5EDjFV",
"9CkpJtAFziWuYSTfadW2rsf4bpF"
]
}
or you can stream it
http://localhost:8098/types/diseases/buckets/infectious/keys?keys=stream

15. Hints - Properties
http://localhost:8098/types/diseases/buckets/infectious/props
{
"props": {
"name": "infectious",
"w": "quorum",
"rw": "quorum",
"r": "quorum",
"pw": 0,
"precommit": [],
"pr": 0,
"postcommit": [],
"notfound_ok": true,
"n_val": 3,
"last_write_wins": false,
"dw": "quorum",
"dvv_enabled": true,
"chash_keyfun": {
"basic_quorum": false,
"allow_mult": true,
"datatype": "set",
"active": true,
"claimant": “riak@127.0.0.1”,
…
}
}

16. Backends
• Bitcask, eLevelDB, Memory or Multi

17. The Cluster

18. The Cluster
A cluster in Riak is a managed collection of nodes
that share a common Ring.

19. The Ring
Figure : Riak Ring, (Redmond & Daily, 2014, P. 11)

20. Replication + Partitions
Figure : Replication Partitions, (Redmond & Daily, 2014, P. 10)
But how?

21. vnodes
Vnodes, are responsible
for claiming a partition in
the Riak Ring, and they
coordinate requests for
these partitions.
n_val = 3
Figure : Riak Ring, (Redmond & Daily, 2014, P. 11)
ring_creation_size = 64
favorite = 75017a36ec07fd4c377a0d2a011400ab193e61db

22. nodes & vnodes
Figure : Riak Ring, (Redmond & Daily, 2014, P. 12)

23. The CAP

24. The CAP
• Consistency (all nodes see the same data at the same
time)
• Availability (a guarantee that every request receives a
response about whether it was successful or failed)
• Partition tolerance (the system continues to operate
despite arbitrary message loss or failure of part of the
system)
CAP loosely states that you can have a C (consistent), A
(available), or P (partition-tolerant) system, but you can only
choose 2, meaning CP or AP.

25. Replication & Write & Read
• n_val=3
• w=all (consistent, high latency)
• r=all (consistent read, high latency)
• w=3,r=1(likely consistent, low latency)
per bucket basis
Figure : NRW, (Redmond & Daily, 2014, P. 14)

26. The Quorum
(floor(N/2) + 1)
• nodes A,B,C,D,E,F,G,L,K,J (Don’t count it, it is 10)
“n_val” : "5"
“w" : "quorum"
• w = floor(5/2)+1
• w=3
• PUT may respond successfully after writing to (A,B,C) and data will be
eventually replicated to (D,E)
why?

27. What about Delete?

28. What about Delete?
• Object are marked as deleted with a
marker(tombstone) and another process(reaper) will
finish deleting the marked objects
• A delete is actually a read and a write
• Checking for the existence of a key(e.g.
MapReduce,List) is not enough to know if an object
exists.
• Check for tombstone metadata(X-Riak-Deleted=true)

29. A Delete Operation
• Client makes the request
• Vnode : update vclock, store with tombstone
• delete_mode = keep, 3000 ms, immediate
• backend flags it as a tombstone (Bitcask or
LevelDB) or wipes it immediately (in-memory)
all r/w/n_val parameters must be met

30. Data Types

31. Data Types
Allows RIAK to make sense of data(a data-aware system),
so it can solve the conflicts.
• Bucket Level: counters, sets, maps
• In Maps : flags(enable, disable) and registers
With and Without DataTypes
[hostAddress]/types/<type>/buckets/<bucket>/keys/<key>
[hostAddress]/types/<type>/buckets/<bucket>/datatypes/<key>

32. Data Type : Set
Adding symptoms to the Influenza
http://localhost:8098/types/diseases/buckets/infectious/datatypes/
D018319
{"add_all":["Headaches", "Fatigue"]}
{"add_all":["Cough", "Sore throat"]}
{"remove": "Cough"}
Result : {["Headaches","Fatigue","Sore throat"]}

33. Data Type : Map
Adding more than symptoms to the Influenza
http://localhost:8098/types/diseases/buckets/infectious/datatypes/D018319
{
"update": {
"symptoms_set": {
"add_all": [
"Headaches",
"Fatigue",
"Sore throat"
]
}
}
}
{
"update": {
"name_register": "Influenza",
"icd-9_register": "487"
}
}

34. Data Type : Map
Adding and removing items from set
{
"update": {
"symptoms_set": {
"remove": "Headaches",
"add": "Fever"
}
}
}
Maps within maps
{
"update": {
"virus_classification_map": {
"update": {
"influenzavirus_A_register": "Some Text",
"influenzavirus_B_register": "Some Text",
"influenzavirus_C_register": "Some Text"
}
}
}
}

35. Data Type : Map
And result is
{
"type": "map",
"value": {
"virus_classification_map": {
"influenzavirus_C_register": "Some Text",
"influenzavirus_B_register": "Some Text",
"influenzavirus_A_register": "Some Text"
},
"symptoms_set": [
"Fatigue",
"Fever",
"Sore throat"
],
"name_register": "Influenza",
"icd-9_register": "487"
},
"context": "g2wAAAABaAJtAAAACCMJ/vlUQtGHYQRq"
}

36. Last but not least
• Search
• Security
• Hooks
• A Little Riak Book : http://littleriakbook.com/

37. Questions!

38. Reference
• Redmond,
E.,
&
Daily,
J.
(2014).
A
Little
Riak
Book.
• Riak
Docs.
http://docs.basho.com/riak/latest/