MongoDB's Replica Sets - Painless scaling and High Availability (HA)

Presentation for NoSQL Roadshow (Basel, Switzerland).

Transcript

1. Replica Sets
   Painless scaling and High Availability (HA)
   Viktor Petersson @vpetersson
   

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2. Who am I?
   {
   name : ‘Viktor Petersson’,
   description : [ ‘geek’, ‘entrepreneur’ ],
   founder_of : ‘wireload’,
   twitter : ‘@vpetersson’,
   email : ‘vpetersson@wireload.net’,
   }
   @vpetersson
   

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3. What is MongoDB?
   @vpetersson
   • Key-value store
   • Schemas less
   • Distributed file system (GridFS)
   • Built-in Map/Reduce
   • Built to scale
   

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4. MongoDB 101
   Relational Database MongoDB
   Database Database
   Table Collection
   Row Document
   Database structure (simplified)
   @vpetersson
   

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5. MongoDB 101
   Relational Database MongoDB
   Master Primary
   Slave Secondary
   Arbiter
   (Hidden)
   Node types
   @vpetersson
   

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6. What are Replica Sets and
   why should I care?
   @vpetersson
   

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7. Typical failover with relational databases
   Master Slave
   Failover IP
   Master Slave
   Failover IP
   Master
   Normal Degraded
   @vpetersson
   (two servers, can lose one)
   

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8. More complex failover with relational databases
   Failover IP
   Normal
   @vpetersson
   Proxies
   Database
   servers
   Failover IP
   Degraded
   (four servers, can lose one of each kind)
   

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9. Failover with MongoDB
   Primary Secondary
   Normal Degraded
   Secondary
   Driver
   Primary Secondary Secondary
   Driver
   Primary
   @vpetersson
   (three servers, can lose two)
   

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10. Primary Secondary
    Down -> Recovering Recovering -> Secondary
    Secondary
    Driver
    Primary Secondary Secondary
    Driver
    Primary
    Secondary
    Primary
    Recovering
    Automatic recovery
    @vpetersson
    

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11. Real life example:
    Taking down the primary for maintenance.
    No dropped connections.
    Primary Secondary
    @vpetersson
    

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12. Creating a Replica Set is dead simple.
    All it takes is three servers (s0, s1, s2) and three commands¹.
    $ mongo
    > rs.initiate()
    > rs.add(‘s1’)
    > rs.add(‘s2’)
    1. After adding “replSet=myRepSet” and “rest = true” to mongo.conf @vpetersson
    

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13. Live demo!
    3 servers with 1 client
    @vpetersson
    

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14. Election
    @vpetersson
    1. Most up to date
    2. Highest priority
    3. Less than 10s behind Primary
    

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15. Configure node priority
    $ cfg = rs.conf()
    $ cfg.members[x].priority = n
    $ rs.reconfig(cfg)
    x = Member id, n = Priority (0 - 100), default is 1.
    @vpetersson
    

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16. Leverage your secondary-nodes
    Warning: Secondaries may be out-of-date.
    Read preference
    • Primary (default)
    • Secondary
    • Secondary_only
    @vpetersson
    

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17. What happens when I’ve
    outgrown my Replica Set?
    @vpetersson
    

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18. @vpetersson
    mongos
    repset0 repset1 repsetN
    Sharding
    

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19. Useful commands
    View server status
    $ db.serverStatus()
    View the replication status
    $ rs.status()
    Step down as Primary
    $ rs.stepDown(n)
    @vpetersson
    

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20. • Improved location awareness
    • Improved concurrent capacity
    • TTL collections
    @vpetersson
    What’s new in MongoDB 2.2?
    Full release notes:
    http://docs.mongodb.org/manual/release-notes/2.2/
    (released yesterday)
    

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21. Summary
    @vpetersson
    • Replica Sets are extremely easy to set up
    • Doesn’t require failover IPs or custom scripts
    • Minimal maintenance
    • Built to scale
    

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22. Questions?
    @vpetersson
    

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23. Thanks to
    @vpetersson
    

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24. Contact me!
    email: info@viktorpetersson.com
    www: viktorpetersson.com
    twitter: @vpetersson
    Also visit
    WireLoad.net
    YippieMove.com
    @vpetersson
    This deck will be available at ViktorPetersson.com.
    

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25. • MongoDB: GridFS, sharding and deploying in the
    cloud (http://goo.gl/1QAV1)
    • MongoDB Replica Set (http://goo.gl/D2pkq)
    • 10gen (http://goo.gl/3m4Kn)
    @vpetersson
    Useful resources
    

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