Architecture

Bootstrap

When starting FlowG, it sets up a single-node cluster automatically. Every node in the cluster needs a unique identifier. If none is given, a random one will be generated.

Once a node joins the cluster, the cluster mesh is updated on every node of the cluster. Replication then happens in the background via the management interface.

Here is a diagram of the bootstrap process:

Transport Endpoints

The protocol is provided on top of FlowG's HTTP management interface:

Cluster Status

Description: Return the currently known local cluster mesh.

GET /cluster/nodes

Response	When
200 OK	On success
500 Internal Server Error	On failure

Example:

{
  "nodes": [
    {
      "node-id": "flowg-node0",
      "endpoint": "http://<private ip address>:9113"
    },
    {
      "node-id": "flowg-node1",
      "endpoint": "http://<private ip address>:9114"
    },
    {
      "node-id": "flowg-node2",
      "endpoint": "http://<private ip address>:9115"
    }
  ]
}

Gossip (Packet mode)

Description: Endpoint used by the SWIM protocol to exchange notifications.

POST /cluster/gossip
Origin: <node endpoint url>
X-FlowG-ClusterKey: <optional cluster cookie>

Response	When
202 Accepted	On success
400 Bad Request	The `Origin` header identifying the node who originated the request
401 Unauthorized	The node requires authentification, and the `X-FlowG-ClusterKey` header was invalid
500 Internal Server Error	On failure

Gossip (stream mode)

Description: Bidirectional endpoint used by the SWIM protocol to exchange data.

POST /cluster/gossip
Upgrade: flowg
X-FlowG-ClusterKey: <optional cluster cookie>

Response	When
101 Switching Protocols	The connection has been accepted, and the socket will be used for bi-directional exchange
501 Not Implemented	The server does not support hijacking the socket, maybe there is a Reverse Proxy in between?
401 Unauthorized	The node requires authentification, and the `X-FlowG-ClusterKey` header was invalid
500 Internal Server Error	On failure

Authentication Database synchronization

Description: Endpoint used to receive incremental backups from other nodes.

POST /cluster/sync/auth
X-FlowG-ClusterKey: <optional cluster cookie>
X-FlowG-NodeID: <remote node ID>
Transfer-Encoding: chunked
Trailer: X-FlowG-Since

... incremental backup data ...

X-FlowG-Since: <new version>

Response	When
401 Unauthorized	The node requires authentification, and the `X-FlowG-ClusterKey` header was invalid
400 Bad Request	Missing HTTP header `X-FlowG-NodeID` or invalid data in HTTP trailer `X-FlowG-Since`
500 Internal Server Error	On failure

Configuration database synchronization

Description: Endpoint used to receive incremental backups from other nodes.

POST /cluster/sync/config
X-FlowG-ClusterKey: <optional cluster cookie>
X-FlowG-NodeID: <remote node ID>
Transfer-Encoding: chunked
Trailer: X-FlowG-Since

... incremental backup data ...

X-FlowG-Since: <new version>

Response	When
401 Unauthorized	The node requires authentification, and the `X-FlowG-ClusterKey` header was invalid
400 Bad Request	Missing HTTP header `X-FlowG-NodeID` or invalid data in HTTP trailer `X-FlowG-Since`
500 Internal Server Error	On failure

Log database synchronization

Description: Endpoint used to receive incremental backups from other nodes.

POST /cluster/sync/log
X-FlowG-ClusterKey: <optional cluster cookie>
X-FlowG-NodeID: <remote node ID>
Transfer-Encoding: chunked
Trailer: X-FlowG-Since

... incremental backup data ...

X-FlowG-Since: <new version>

Response	When
401 Unauthorized	The node requires authentification, and the `X-FlowG-ClusterKey` header was invalid
400 Bad Request	Missing HTTP header `X-FlowG-NodeID` or invalid data in HTTP trailer `X-FlowG-Since`
500 Internal Server Error	On failure

Bootstrap​

Transport Endpoints​

Bootstrap

Transport Endpoints