CockroachDB Scalable, survivable, strongly consistent, SQL presented by Ben Darnell / CTO
About Me • Co-founder of Cockroach Labs • Previously at Google, Dropbox, Square @cockroachdb
Agenda ● Motivation ● High-level architecture ● Some CockroachDB Features ● Q & A ● Interruptions are encouraged! @cockroachdb
Motivation @cockroachdb
Limitations of Existing Databases Relational NoSQL Hard to scale horizontally Scalability with strings attached ● ● Scalability: manual sharding Limited transactions: developer results in high operational burden due to complex data complexity and application modeling OR ● rewrites Limited indexes: lost flexibility ● Replication: wasted resources with querying and analytics ● (stand-by servers) or lost Eventual consistency: consistency (asynchronous correctness issues and higher replication) risk of data corruption @cockroachdb
CockroachDB: The Best of Both Worlds • Single binary/symmetric nodes • Applications see one logical DB, including cross-datacenter, global • Self-healing/self-balancing • Scale out is as simple as adding nodes • SQL @cockroachdb
High-Level Architecture @cockroachdb
Abstraction Stack SQL Transactional KV Distribution Replication Storage @cockroachdb
Transactional KV • Monolithic sorted key-value map SQL • Automatically replicated and distributed Transactional KV • Consistent Distribution • Self-healing Replication @cockroachdb
Transactional KV: ACID • Atomicity. All operations or no operations. SQL • Consistency. No violating constraints. Transactional KV • Isolation. Exclusive database access. Distribution • Durability. Committed data survives crashes. Replication @cockroachdb
SQL: Structured Data Model Inventory ● Tables @cockroachdb
SQL: Structured Data Model Inventory ● Tables ● Rows @cockroachdb
SQL: Structured Data Model Inventory ID Name Quantity ● Tables 1 Glove 1 ● Rows ● Columns 2 Ball 4 3 Shirt 2 4 Shorts 12 5 Bat 0 6 Shoes 4 @cockroachdb
SQL: Structured Data Model Name_Idx Inventory Name ID Name Quantity ● Tables Ball 1 Glove 1 ● Rows ● Columns Bat 2 Ball 4 ● Indexes Glove 3 Shirt 2 Shirt 4 Shorts 12 Shoes 5 Bat 0 Shorts 6 Shoes 4 @cockroachdb
SQL CREATE TABLE inventory ( SQL id INTEGER PRIMARY KEY, Transactional KV name VARCHAR, Distribution quantity INTEGER, Replication INDEX name_index (name) ); @cockroachdb
SQL: Key anatomy INSERT INTO inventory VALUES ( 1 , ‘Apple’ , 12 ); INSERT INTO inventory VALUES ( 2 , ‘Orange’ , 15 ); id name quantity key /<table>/<index>/<key>/<column> Value 1 Apple 12 / inventory /primary/ 1 / name Apple = / inventory /primary/ 1 / quantity 12 2 Orange 15 / inventory /primary/ 2 / name Orange / inventory /primary/ 2 / quantity 15 @cockroachdb
Distribution: Sharding The data is split into ~64MB ranges . Each holds a contiguous range of the key space. Ø-lem lem-pea pea-∞ peach apricot lemon banana lime pear blueberry mango pineapple cherry melon raspberry grape orange strawberry @cockroachdb
Distribution: Index An index maps from key to range ID shard index Ø-lem lem-pea pea-∞ Ø-lem lem-pea pea-∞ peach apricot lemon banana lime pear blueberry mango pineapple cherry melon raspberry grape orange strawberry @cockroachdb
Distribution: Split Split when a range is too large (or too hot, or…) shard index Ø-lem lem-pea pea-str str-∞ Ø-lem lem-pea pea-str str-∞ peach strawberry apricot lemon banana lime pear tamarillo blueberry mango pineapple tamarind cherry melon raspberry grape orange @cockroachdb
Replication: Survivability ● Each range is replicated to three or more SQL nodes Transactional KV ● Consensus via Raft Distribution ● "Leaseholder" optimization to allow reads Replication to be served without consensus ● Multi-Version Concurrency Control @cockroachdb
Data Distribution: Placement Node 1 Node 2 Node 3 Range 1 Range 1 Range 1 Each range is replicated Range 2 Range 2 Range 2 to three or more nodes Range 2 Range 3 Range 3 Range 3 @cockroachdb
Data Distribution: Rebalancing Node 1 Node 2 Node 3 Range 1 Range 1 Range 1 Adding a new (empty) Range 2 Range 2 Range 2 node Range 2 Range 3 Range 3 Range 3 Node 4 @cockroachdb
Data Distribution: Rebalancing Node 1 Node 2 Node 3 Range 1 Range 1 Range 1 A new replica is Range 2 Range 2 Range 2 allocated, data is Range 2 Range 3 Range 3 Range 3 copied. Node 4 Range 3 @cockroachdb
Data Distribution: Rebalancing Node 1 Node 2 Node 3 Range 1 Range 1 Range 1 The new replica is made Range 2 Range 2 Range 2 live, replacing another. Range 2 Range 3 Range 3 Range 3 Node 4 Range 3 @cockroachdb
Data Distribution: Rebalancing Node 1 Node 2 Node 3 Range 1 Range 1 Range 1 The old (inactive) replica Range 2 Range 2 Range 2 is deleted. Range 2 Range 3 Range 3 Node 4 Range 3 @cockroachdb
Data Distribution: Rebalancing Node 1 Node 2 Node 3 Range 1 Range 1 Range 1 Process continues until Range 2 Range 2 nodes are balanced. Range 2 Range 3 Range 3 Node 4 Range 2 Range 3 @cockroachdb
Data Distribution: Recovery X Node 1 Node 2 Node 3 Range 1 Range 1 Range 1 Losing a node causes Range 2 Range 2 recovery of its replicas. Range 2 Range 3 Range 3 Node 4 Range 2 Range 3 @cockroachdb
Data Distribution: Recovery X Node 1 Node 2 Node 3 Range 1 Range 1 Range 1 A new replica gets Range 2 Range 2 created on an existing Range 2 Range 3 Range 3 Range 3 node. Node 4 Range 1 Range 2 Range 3 @cockroachdb
Data Distribution: Recovery Node 1 Node 3 Range 1 Range 1 Once at full replication, Range 2 Range 2 the old replicas are Range 2 Range 3 Range 3 forgotten. Node 4 Range 1 Range 2 Range 3 @cockroachdb
Some CockroachDB Features @cockroachdb
Geographic Zone Configurations ● Control where your data is ● Nodes are tagged with attributes and hierarchical localities ● Rules target these ● Zero downtime data migrations @cockroachdb
Geo-Partitioning ■ Domicile data according to customer ○ Meet regulatory constraints ○ Low-latency reads / writes ■ One logical database ○ Simplified app development @cockroachdb
Distributed SQL SELECT l_shipmode, AVG(l_extendedprice) FROM lineitem GROUP BY l_shipmode; @cockroachdb
Online Schema Changes • Based on Google's F1 Paper • State machine, possibly with backfill • Zero downtime @cockroachdb
Questions? jobs@cockroachlabs.com github.com/cockroachdb www.cockroachlabs.com
Other Topics • (New in 2.1) Query optimizer • Testing with Jepsen • Graphical admin UI • Distributed import @cockroachdb
Backup/Restore • Distributed • Consistent to a point in time • Incremental @cockroachdb
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