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Back to Basics 2017: Introduction to Sharding
The document outlines a webinar on sharding in MongoDB, covering its definition, architecture, and constraints. It details the process of building a sharded cluster, including key considerations such as shard keys and data distribution. Additionally, it addresses balancing the cluster and routing requests effectively.
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Back to Basics 2017: Introduction to Sharding
- 2. Back to Basics2017 : Webinar 4 Introduction to Sharding Joe Drumgoole Director of Developer Advocacy, EMEA MongoDB @jdrumgoole V1.1
- 3. 3 Summary of Part1 to 3 • Introduction to NoSQL • Your First MongoDB Application • Introduction to Replica Sets • MongoDB Compass, MongoDB Atlas
- 4. 4 Agenda • Sharding –What is it? Why do we need it? • The architecture of a sharded cluster • Sharded cluster constraints • How a sharded cluster works in practice
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- 6. Replica Set withMongoDB Application Driver Primary /data Secondary /data Secondary /data
- 7. Replica Set Bottlenecks Application Driver Primary /data Secondary /data Secondary /data RAMLimits on single server CPU Limits on single server Network Bandwidth Disk I/O
- 8. What is Sharding? Application mongosmongos mongos Driver
- 9. But There isMore Application mongos mongos mongos Driver Config Server
- 10. 10 Construction • Build Cluster •Identify shard key • Sharding happens on individual collections • To shard a collection: sh.shardcollections( "MUGS.members",{ "members.member_id" : 1 } )
- 11. 11 Shard Keys • Userdefines shard key • Shard key defines range of data • Key space is like points on a line • Range is a segment of that line
- 12. 12 Shard Key Constraints •Shard keys are immutable • Shard keys should have high cardinality • Shard keys must be unique • Shard key must exist in every document • Limited to 512 bytes in size • Cannot be a multi-key (array)
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- 14. 14 Chunk is aSection on the Range
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- 16. 16 How Data isDistributed • Initially 1 chunk • Default max chunk size: 64mb • MongoDB automatically splits & migrates chunks when max reached
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- 23. 23 Routing Requests -Targeted
- 24. 24 Routing Requests –Non-Targeted
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- 26. 26 Picking a ShardKey • Cardinality • Write Distribution • Query Isolation
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Editor's Notes
- #3 Who I am, how long have I been at MongoDB.
- #9 Data is partitioned. Mongos distribute data.
- #10 Data is partitioned. Mongos distribute data.
- #16 Once chunk size is reached, mongos asks mongod to split a chunk + internal function called splitVector() mongod counts number of documents on each side of split + based on avg. document size `db.stats()` Chunk split is a **logical** operation (no data has moved) Max on first chunk should be 14
- #18 Balancer is running on mongos Once the difference in chunks between the most dense shard and the least dense shard is above the migration threshold, a balancing round starts