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Everybody likesREDIS
Liviu Costea @clm160 Software Developer
Biz Pro Technologies 23.09.2015
Let me help you add Redis to your stack today!
Agenda
What’s all this with Redis?
Advanced structures (real usage scenarios)
Features, many features
How and where to use it
Bit of history
There was a developer (@antirez) and he had a problem: real time web analytics
NOT a plain Key-value NoSql database but a in memory data structures server
VMWare, Pivotal, RedisLabs and many other companies helped in some way
Very popular: Twitter, Airbnb, Flickr, StackOverflow, GitHub, BitBucket, Biz Pro Technologies and many others
How people start
First there was a server, then you think of scaling
Next you have 2 servers, but how do you share:◦Session◦Cached & static items◦Sometimes you need to synchronize them
Then you find some solutions:◦Database (probably the worst)◦Memcached (getting better)◦Redis (a NoSQL, newest addition)
Data structures
Main data types:◦Strings (everything is a string)◦Lists (double linked lists)◦Sets (unique lists)◦Hashes (like an object)◦Sorted sets (by a value at creation)
Efficiently modeling of data is your main concern!
Queries
You don’t have queries, you don’t have indexes
You do have◦KEYS = returns all your keys (EVIL I tell you!)◦SCAN with MATCH, COUNT = server side cursor
But these are not for real queries, instead you should
keep your data updated by yourself: queries, indexes
DEMO 1
1. Data model for a voting based website
2. Query to get all developers from Iasi
Single threaded serverDon’t block it with long operations (#1 threat in production is KEYS command)
Single threaded server
There is no locking necessary
Extremely fast, everything is in RAM
Limited support for transactions with optimistic locking (might be removed in the future versions)
Pipelining support (check your client)
Lua scripting
Similar to stored procedures:◦They are atomic by nature, but not transactions◦Rule of thumb: don’t write heavy scripts because you block the server◦Limitation: use only deterministic functions (because of replication model)◦KEYS and ARGV global variables
DEMO 2
1. Sliding expiration for a simple key
2. Increment all scores of a set
3. Distributed locking
Use as a cache system
It can be configured as a LRU cache with max memory and different eviction policies
Expiration (TTL) of keys only (no subkeys)
Use as a session storage
If you go with the session out of proc here are some existing session providers:◦PHPRedis◦Spring Session◦Ruby◦Node.js◦ASP.NET (official and open source - wow)
Use as a real database
Backup – Snapshot (RDB file) - default◦BGSave – fork◦On Stop / On Start
Persistence - AOF◦Every write appends
Use both, on long term they will be unified
Master / Slave replication and WAIT command
DEMO 3
1. Restarting the server, data is not lost
2. Save on demand
3. Lets see also AOF
More features
Big ecosystem, lots of client libraries out there: redis.io/clients
On AWS and Azure – first class citizen (with high availability)
Windows port by MS Open Tech (good for dev)
GUIs:Redsmin (web), Redis-commander (web, your own
installation, node.js), FastoRedis (desktop)
Redis Cluster
Available from 3.0 – waiting for adoption – clients and applications
Implemented with query routing
Client must be (smart) able to memorize things about the cluster: gets redirected to the right node
Ping – Pong between clients (heartbeat)
Keyspace (dividing data into nodes)
Generating KEYS in a LUA script isn’t cluster-safe
Troubleshooting
Main problems come from long running commands:◦FLUSHDB,◦FLUSHALL,◦KEYS◦LUA Scripts◦They can even bring your replica set DOWN
DEMO 4
1. Slowlog
2. Big keys
3. Monitor
Future features
For the next version
◦Geo hashing API (already documented)
◦A few new commands: like a memory introspection command
Other things in the queue:
◦Real transactions with Lua, support for rollback
