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GoQuorum qlight

A qlight node is a lightweight replica of a full node that proxies transactions to the full node. You can configure a qlight node to reduce the amount of data shared with external parties by the full nodes.

You can use a qlight node to:

  • Avoid impacting transaction-processing main nodes with anything that could thrash the API (such as monitoring, state querying, or other intensive processes).
  • Prevent security concerns where the main node is handling multiple private parties (multi-tenancy). The qlight client deals with a private state for one party only, and only that user has access to the qlight client.

Standard nodes and qlight nodes​

A standard GoQuorum node processes all blocks and associated transactions. It also requires a local private transaction manager to handle private data. This can require significant resources and make it more difficult to scale networks. Also, since the node processes all transactions, this can raise privacy concerns.

Using a qlight node for process-intensive tasks can help improve the performance of a main node. qlight nodes help prevent network throttling due to third party network limits, or multiple clients all hitting the same main node.

Unlike standard GoQuorum nodes, qlight nodes:

  • Depend on a server full node for receiving data and only connect to the server node. There's no communication with any other node.

  • Only receive blocks from the server node, processing them locally to build up the public and private state.

  • Don't require a transaction manager. Instead, private data is sent directly by the server node via the qlight P2P protocol.

  • Act as a proxy for locally submitted transactions, performing minimal validation. API calls such as SendTransaction/SendRawTransaction/StoreRaw are forwarded to the server node for processing.

  • Use the same RPC APIs required for dapps, delegating calls to the server node if needed.

  • Don't participate in the consensus mechanism.

Client and server​

  • qlight client refers to the qlight node.

  • qlight server refers to a full node configured to supply data to the qlight client. It also handles API requests that are delegated from the qlight client.

Architecture​

qlight architecture

Communication protocol​

The qlight client and server communicate through a peer-to-peer protocol.

Security​

The following are security features available for the qlight client-server connection:

Private transaction manager cache​

The qlight client doesn't have a local private transaction manager, but relies on the qlight server to supply private data. This is implemented using a local cache that simulates a local private transaction manager. Private transactions can be executed locally, with the private data being fetched from the private transaction manager cache.

API methods (on qlight server)​

  • admin.qnodeInfo - Returns details of the qlight configuration.
  • admin.qpeers - Returns details of the connected qlight clients.