Expanding Ogmios Mempool Functionality to HTTP

[marcusbfs]

What is your idea? Provide a use case.

We’re improving cardano-transaction-lib (CTL) and aim to switch from WebSocket to HTTP when interfacing with Ogmios, to reuse existing code and simplify maintenance. However, some CTL projects depend on Ogmios’s mempool functionality (e.g. hasTransaction, nextTransaction, sizeOfMempool, releaseMempool), which currently can’t be accessed via HTTP since they require an acquired mempool snapshot.

We propose adding a stateless mempool API to Ogmios, letting developers manipulate the mempool over HTTP without maintaining a WebSocket connection—streamlining HTTP-only integrations.

Why is it a good idea?

• Consistent HTTP interface: Ogmios already provides a stateless HTTP interface for many queries; extending it to mempool operations would let developers use a single protocol for all features.
• Reduced complexity: projects needing only HTTP can avoid managing WebSockets, lowering both implementation and maintenance effort.
• Wider accessibility: some environments do not support WebSockets or make them cumbersome to use. An HTTP-based approach to mempool operations removes this barrier and broadens Ogmios’s usability.

What is the current alternative and why is it not good enough?

• Keep using WebSockets: currently, you must open a WebSocket connection, acquire the snapshot, then call the mempool methods. This is overkill for simpler or one-off queries, and adds complexity if you are already using the HTTP interface
• Extract websocket-based mempool support into a separate package: splitting off these features increases complexity and confuses users who only want an HTTP endpoint, forcing them to manage multiple protocols unnecessarily.