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Mining Asynchronous Services

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Note: This documentation describes the behavior as of PR #1073. Implementation details may change as the protocol evolves.

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The bridge represents a WebSocket bridge between the gateway and the service backend. It handles the forwarding of relay requests from the gateway to the service backend and relay responses from the service backend to the gateway.

Asynchronous Message Handling​

Due to the asynchronous nature of WebSockets, there isn't always a 1:1 mapping between requests and responses. The bridge must handle two common scenarios:

1. Many Responses for Few Requests (M-resp >> N-req)​

In this scenario, a single request can trigger multiple responses over time. For example:

  • A client subscribes once to an event stream (eth_subscribe)
  • The client receives many event notifications over time through that single subscription

2. Many Requests for Few Responses (N-req >> M-resp)​

In this scenario, multiple requests may be associated with fewer responses. For example:

  • A client uploads a large file in chunks, sending many requests
  • The server only occasionally sends progress updates

Design Implications​

This asynchronous design has two important implications:

  1. Reward Eligibility: Each message (inbound or outbound) is treated as a reward-eligible relay. For example, with eth_subscribe, both the initial subscription request and each received event would be eligible for rewards.

  2. Message Pairing: To maintain protocol compatibility, the bridge must always pair messages when submitting to the miner. It does this by combining the most recent request with the most recent response.

Future Considerations​

Currently, the RelayMiner is paid for each incoming and outgoing message transmitted. While this is the most common and trivial use case, future services might have different payable units of work (e.g. packet size, specific packet or data delimiter...).

To support these use cases, the bridge should be extensible to allow for custom units of work to be metered and paid.