Cluster Sharding

in Effect

Warehouse

a concurrency example

User 1

User 2

System 1

Stock A

System 2

Stock A

Create Order

Create Order

1. Read the stock
2. Verify the stock
3. Write the transaction

1. Read the stock
2. Verify the stock
3. Write the transaction

Global Lock

• Acquire some kind of global lock between services/servers
• Perform the write
• Release the lock

Single Writer

• Redirect the write request to a single entity that will handle request

Warehouse

a concurrency example

User 1

User 2

System 1

redirect

System 2

redirect

Create Order

Create Order

1. Read the stock
2. Verify the stock
3. Write the transaction

System 3

Stock A

What is Shardcake?

• Single writer: Ensures each entity is running only in one place
   
• Location transparency: Communicate with entities with just their ID, without knowing their location

Inspired by the original scala library
by devsisters

Keywords

• Entity: defines a behaviour
• Pod: Hosts many entities
• Shard: A grouping of instances of entities
• Assignments: A correlation between Pod and Shard
• Shard Manager: Single instance that supervises and performs assignments

How it works?