This presentation was used in a Redis talk that took place in ALT.NET Melbourne at February 25th, 2014. It is aimed for .Net developers, though almost all of the slides solely discuss Redis as the data store server, without any relation to client libraries in general and .Net in particular.

1. Ofer Zelig
@oferzelig

2. What is Redis?
• Key-Value Store / “Data Structure Server”
• Value data types: string, list, set, sorted set, hash
• Memory-based
which means…
very fast reads and writes!!
•
BUT with disk persistence, so you enjoy all the goods
• The only limitation is physical memory on the machine.

3. What is Redis?
• Extremely easy to use; clearly documented
• Mainly used as Cache layer but some use it as their
first-class database
• Hmm… and BTW… it’s also a great Pub/Sub engine!
• All of its config is done in one very clear text file
• DEMO
• Single-threaded

4. Redis vs Memcached
• Rich set of data types, not just key-value pairs
• Supports persistence, you don’t lose what’s in the
RAM when server reboots
• Replication out-of-the-box
• You can even create replication trees

5. What is Redis?
• Open Source (BSD 3-Clause)
• Written by Salvatore Sanfilippo (@antirez)
and other very smart contributors
• Full time sponsored by VMware and now by Pivotal

6. Who uses Redis?
I’ve almost forgot…
Source: http://blog.togo.io/redisphere/redis-roundup-what-companies-use-redis/

7. DATA TYPES

8. DATA TYPES
STRING
users:1
{name:’John’,email:’a@b.com’}
images:5
#h•ChhµLT5•OJ
z‹ H
• Up to 2^32 bits (512MB) in each key!
• Binary safe
• Can hold, and ideal for:
• Plain strings – page/post cache etc.
• Full JSON objects
• Raw bits / flags (great usage: realtime metrics – daily
active users - http://blog.getspool.com/2011/11/29/fast-easyrealtime-metrics-using-redis-bitmaps/)
• Even binary file content (hence binary file
manipulation for example)

9. DATA TYPES
STRING
users:1
{name:’John’,email:’a@b.com’}
images:5
#h•ChhµLT5•OJ
• Examples:
•
•
•
•
SET
GETSET
SETBIT
INCR, INCRBY
z‹ H

10. DATA TYPES
STRING
users:1
{name:’John’,email:’a@b.com’}
images:5
#h•ChhµLT5•OJ
z‹ H
• Sample usages:
• Lock:
SET resource-name anystring NX EX max-lock-time
• General Cache
• Flags
• Picture masking (BITOP)
• A/B Testing stats

11. DATA TYPES
bus:messages
1
LIST
4
{age:3}
1
• Up to 2^32 elements in each key (about 4 billion!)
• Internally maintained as linked-lists
• O(N) - Extremely fast near both ends of the list, less
in the middle
• Ideal for:
• Queues (private and shared)
• Stacks
• Top N, Recent News

12. DATA TYPES
bus:messages
1
LIST
4
{age:3}
• Examples:
•
•
•
•
LPUSH / RPUSH / LPOP / RPOP
RPOPLPUSH
LRANGE
BLPOP / BRPOP
1

13. DATA TYPES
bus:messages
1
LIST
4
{age:3}
1
• Sample usages:
• Timeline of a social network – LPUSH to add new
items, LRANGE to retrieve most recently added items
• LPUSH+LTRIM together to always keep top/latest N
• Useful for logging of recent user actions / errors
• RPOPLPUSH using same source and destination to
create a rotation of “ring” of items
• Blocking/waiting

14. DATA TYPES
page:home:uniquevi
sitors:20140225
•
•
•
•
80.55.203.40
SET
201.3.14.185
55.67.100.120
40.77.232.204
Maintains a unique set of items (but unordered)
Up to 2^32 members in each key (about 4 billion)!
Supports intersections, unions etc.
Quickly check whether a member exists –
SISMEMBER - O(1)
• Ideal for:
• Storing relations (i.e. followers, friends etc.) – the key
represents the User ID, the value (set members) is the
users they follow.

15. DATA TYPES
page:home:uniquevi
sitors:20140225
80.55.203.40
SET
201.3.14.185
55.67.100.120
40.77.232.204
• Examples:
• SRANDMEMBER / SPOP
• SINTERSTORE / SUNIONSTORE / SDIFFSTORE etc.
• Sample usages:
• Tracking unique IPs (just use SADD every view, then use
SCARD whenever you want)
• Tagging: Use a set for each tag (each member is, say, a
picture ID). You can easily get all pictures that have 3
different tags using SINTER
• Extract random members (ads, lottery balls, tip of the day…)
using SPOP / SRANDMEMBER

16. DATA TYPES
SORTED SET
sam
Leaders
neville
devon
matt
4236
5870
7615
7615
• Same as set, but ordered
• The order is defined by score. Each member has a score
assigned to.
• Up to 2^32 members in each key (about 4 billion)!
• Supports intersections, unions etc. – basically all commands
that a SET supports
• O(LOG(N)), O(N) and such
• But hey! It’s still a millisecond or so even for big sorted sets
• Sorting takes place upon insert, so queries for ranges, even in the
middle, are still fast
• Members are still unique, but scores may be repeated.

17. DATA TYPES
SORTED SET
sam
Leaders
neville
devon
matt
4236
5870
7615
7615
• Sample usages:
• Maintain a leader board of a game, get top X etc.
• In general, any top something. Such as top posts by
pageviews etc.
• Index other data in Redis. For example: a sorted set
where each member is a user ID and the score is their
age. You can query for all users within a given age
range.
• Search text statistics

18. DATA TYPES
HASH
name
age
29
gender
m
active
user:13
Bob
1
• If Redis keys/values are a big hash, then a HASH key
holds a value that is itself a HASH
• But that can’t be nested further
• Up to 2^32 key/value pairs in each hash
• Fields in a hash can still be atomically incremented,
for example

19. DATA TYPES
HASH
name
age
29
gender
m
active
user:13
Bob
1
• Sample usages:
• Saving properties of a business object (very similar to
plain DB table)
• Saving sessions & CSRF tokens
• Maintaining many-to-many mappings and such

20. PERSISTENCE
• Two options: RDB and AOF
• Each has advantages & disadvantages (of course…)

21. PERSISTENCE
RDB
• Point-in-time snapshot of all dataset
• Compact, ideal for regular backup/archive, can be
delivered to S3 etc.
• Multiple save-points available, set in redis.conf

22. PERSISTENCE
•
•
•
•
AOF == Append Only File
Writes every command, like a tape
Gets re-written when it gets too big
Can be easily parsed & edited
AOF

23. PERSISTENCE
OK, so what should I use?
• I don’t have clear answer, as always “it depends”
• Visit http://redis.io/topics/persistence for much
more explanation including “What Should I Use”
• Bottom line – defaults are OK, just start and worry
about that when your app gets bigger

24. KEY EXPIRATION
• Each key can be set to expire:
• EXPIRE / EXPIREAT
• There is at least one command that allows setting
expire time within the command: SETEX
• Cancel expiration - PERSIST
• TTL - returns the remaining time to live of a key
that has a timeout.
• Overwrite of a whole key (i.e. SET) clears the
timeout.

25. KEY EXPIRATION
• Updating a value doesn’t clear and doesn’t reset the timeout.
• Very interesting read on how Redis actually deletes expired
keys - http://redis.io/commands/expire
• Global expiration policy can be set in redis.conf.
Ideal: when Redis is used as a cache layer:
• maxmemory 2mb
maxmemory-policy allkeys-lru
• There are more options – read the comments inside
redis.conf

26. MULTI / EXEC
•
•
•
•
•
Transactions
Very safe, no other conflicting clients in the middle
Persistency safe
Optimistic locking using WATCH
EVAL and Lua Scripts

27. PUB / SUB
• SUBSCRIBE / PUBLISH
• Very easy (DEMO)
• Example usages:
• Chat
• Bus

28. GLOBAL COMMANDS
•
•
•
•
•
•
•
KEYS / SCAN / SSCAN / HSCAN / ZSCAN
SELECT / DBSIZE
PING / ECHO
INFO / INFO ALL / TIME
MONITOR
SAVE / BGSAVE
CLIENT LIST / CLIENT KILL
• Advanced: SORT (http://redis.io/commands/sort)

29. BENCHMARKS
• http://redis.io/topics/benchmarks
• DEMO: redis-benchmark -q

30. MAKING REDIS EVEN FASTER
• Pipelining
• EVAL and Lua Scripts

31. SERVER
• Windows setup
• https://github.com/MSOpenTech/redis
• Currently v2.6.12
• For development only
• Linux setup
•
•
•
•
Recommended for production
Currently v2.8.6
First of all, don’t be afraid!
Clear instructions on the Redis site
• http://redis.io/topics/quickstart
• You can skip most manual steps and just run a server
installation script:
• http://download.redis.io/redis-stable/README

32. .NET CLIENTS
• ServiceStack.Redis
• https://github.com/ServiceStack/ServiceStack.Redis
• BookSleeve
•
•
•
•
https://code.google.com/p/booksleeve/
Written by Marc Gravell from Stack Exchange
Pipelined, Task API, async/await etc.
Maintain 1 connection throughout the app
• http://stackoverflow.com/a/8777999/290343
• DEMO

33. MANAGERS / VIEWERS
• Redsmin - https://redsmin.com/
• Robust
• Priced (except for a very basic plan)
• SaaS
• Redis Desktop Manager - http://redisdesktop.com/
• Open Source Desktop GUI
• Pretty basic
• redis-commander - https://github.com/joeferner/redis-commander
• Node.js, Open Source
• Pretty basic

34. Clustering
• A long task in process, current Alpha-grade code
•
•
http://redis.io/topics/cluster-tutorial
http://redis.io/presentation/Redis_Cluster.pdf
• In the mean time:
• Replication (master / slaves) – works great
• Redis Sentinel: http://redis.io/topics/sentinel
• A system designed to help managing Redis instances
• Monitoring. constantly checks if master and slave instances are
working as expected.
• Notification. notify sysadmin or other program, that something
is wrong with one of the monitored Redis instances.
• Automatic failover. if the master failed (a slave is promoted to
be master, everyone is updated).

35. Resources
• http://redis.io – Main Redis site
• Clients, servers, full documentation
• Interactive tutorial - http://try.redis.io/
• The Little Redis Book - http://openmymind.net/redis.pdf
• Various Stack Exchange articles about their infrastructure
including Redis:
• Canonical answer about Stack Exchange cache layers:
http://meta.stackoverflow.com/a/69172
• Great answer from Antirez himself about usage of the
different data types:
• http://stackoverflow.com/a/9626334

36. SO WHAT ARE YOU
WAITING FOR?
 Super fast
 Easy to install & maintain
 Stable & robust
 Easy to consume with .Net
 High quality documentation