Gossip Key-Value Store

Architecture

The Gossip Key-Value Store is a distributed key-value store that uses a gossip protocol to replicate data across all members of the cluster. The key-value store is eventually consistent and is designed to be used in scenarios where strict consistency is not a hard requirement.

Data Model

Data stored in the key-value store is modelled as three level hierarchy Namespace > Table > Rows.

┌──────────────┐              
│  Namespace   │             
└─┬────────────┘              
  │    ┌──────────────┐       
  └────┤    Table     │       
       └─┬────────────┘       
         │    ┌──────────────┐
         └────┤     Row      │
              └──────────────┘

Represented as JSON, the data model looks like this:

{
  "sys": {
    "members": {
      "member_id": {
        "protocols": [
          {
            "name": "gossip",
            "endpoint": "..."
          },
          {
            "name": "...",
            "endpoint": "..."
          }
        ]
      }
    }
  },
  "usr": {
    "table_A": {
      "key_1": "value_1",
      "key_2": "value_2"
    },
    "table_B": {
      "key_1": "value_1",
      "key_2": "value_2"
    }
  }
}

Note that JSON is used here for illustrative purposes only - it isn't the actual data format used by the key-value store.

Namespace

A namespace is a group of tables. There are only two namespaces in the key-value store: sys and usr. The sys namespace is reserved for system data and is used by the key-value store itself. The usr namespace is used for user data.

sys Data

Members

The members table contains information about all the members in the cluster. Each member is identified by a unique member_id.

Protocols

Each member exposes a set of protocols and endpoint that can be used to communicate with it. For example, every member exposes the gossip protocol which is used by the key-value store to replicate data across the cluster.

usr Data

The usr namespace is used to store user data. The data is stored in tables and rows. Each table is a collection of rows where each row is a key-value pair. Values are stored as strings and are not interpreted by the key-value store.

Unit Testing

A deterministic unit test suite is provided for the key-value store and the replication protocols. See the unit tests on server.rs for more.

Deployment

Local (Minikube) Deployment

For local development and testing, the key-value store can be deployed on Minikube. See Minikube Deployment for more information.

AWS Deployment

See AWS Deployment for more information.