NoSQLMongoDB and Redis as alternatives to

traditional RDBMS

Then...

...and now

*This thing weighs less than 50g

Meaning of NoSQL

1970 = We have no SQL1980 = Know SQL2000 = No SQL!2005 = Not only SQL2014 = No, SQL

(slide adapted from @markmadsen)

MongoDB

MongoDB

● it is the “new MySQL”● Project started in 2007 by 10gen (now MongoDB Inc)● Cross-platform, open-source● 5th most used DBMS & most used Document Store*

(next DS CouchDB - 21st)* According to db-engines.com as of Oct 2014

Characteristics

● “It's really a hybrid database with features from a few different places.” (Gaetan Voyer-Perrault on Quora)

● Document Oriented but NO SCHEMA! ● Documents grouped in Collections● Binary JSON (BSON) format● Load Balancing (automated sharding, sharding key

can be user defined)● Replication (Replica Sets)● Automated failover

Characteristics - continued

● Primary and Secondary Indexes● JavaScript for UDF● MapReduce● Capped Collections● Aggregation Framework since 2.2● Ad-hoc Query Support

Caveats

Generic performance tips

● Use 64-bit OS● Lots of RAM, fast disks (was anyone expecting

something else?)● ensure that at least indexes + working set fit in RAM

(db.stats(), db.<coll>.stats()) - if not, you might want to try TokuMX

● Design for de-normalized data models

Generic performance tips

● Write-Concerns● Shard early● Fixed (or at least bounded) record size => better write

performance● Use short attribute names (reduces index & data size,

OFC!)● EXT4 or XFS

IRL

● virtualized server 8G RAM, 4 vCPU - no sharding, no replica sets

● 100 inserts/s , 130M doc collection WITH secondary index (avg doc size 0.6k)

● 20 inserts/s 3M doc collection WITH 18 secondary indexes (avg doc size 10k)

Use Cases

● Logs● Location Data (Mongo has built in Geospatial ops)● Account and User Profiles● Messaging● (complex) Config Data● http://www.mongodb.com/who-uses-mongodb (hint:

Expedia, Business Insider, The Weather Channel, Foursquare, eBay)

Redis

Redis

● Salvatore Sanfilippo (@antirez)● Started in 2009● Key-Value Store● 11th most used DBMS & most used KV Store* (next

KVS memcached - 19th)● Sponsored by Pivotal (spinoff EMC/VMware)* According to db-engines.com as of Oct 2014

Characteristics

● Holds all data in memory, persists on disk● Data Models

○ Strings/Blobs/Bit-Maps (not really Bitmaps)○ Hashtables○ Linked Lists○ Sets○ Sorted Sets

● HyperLogLog (+2.8.9 - trade accuracy for memory)● Master Slave Replication● High Availability (through Sentinel)

Characteristics - continued

● Redis Cluster in works (not production ready yet) - sharding ○ asynchronous replication○ does not guarantee strong consistency (may ‘forget’ writes)

● AOF sync - default 2s● Does not support secondary indexes● Pub/Sub mode since 2.0● Key expiry● Server scripting with Lua

IRL

● virtualized server 4G RAM, 1vCPU● +50k get/set per second (redis-benchmark)● only 128 queries out of 1165550375 over 10ms

(0.00001%)○ uptime_in_days:439○ used_memory_human:424.09M○ used_memory_peak_human:834.94M○ total_connections_received:1352935○ db0:keys=610884,expires=355397

Generic performance tips

● Use short key names (reduces data size, OFC!)● You can create secondary indexes (but you have to

maintain them, e.g. using SET)● You can have ad-hoc queries (actually is query) :

using SORT

Use Cases

● Cache● IPSS/IPC● Queue mechanisms (see e.g. Resque)● Log/Task buffers● Statistics and aggregation datastore● (anywhere you use memcached)● http://redis.io/topics/whos-using-redis (hint: Twitter,

GitHub, Snapchat, StackOverflow a.o.)

Recap

One size does NOT fit all!

Further reading

● Must read: http://blog.andreamostosi.name/big-data/ (almost exhaustive list of all things NoSQL and BigData)