Architecture Decision Record: Offline Broadcast

Title: Record: Offline Broadcast

status

In progress

Updated on 15-06-2025

contributors

• Main contributor(s): fmar

• Reviewer(s): fmar, leo, nogringo

• Final decision made by: fmar, leo, nogringo

Context and Problem Statement

NDK does not remember events broadcasted when offline. As a user, I want to be able to draft something in a remote location (e.g. plane) without thinking about Nostr relay constraints.

Main Proposal

Requirements:

• relay specific

• gossip

• Consider done %

• different modes, specific: relay broadcast must succeed

• eviction policy (keep in cache, delete old ones)

• Streamlined reject handling (retry, dismiss, paymentRequired, POW, blocked, etc.)

• Gossip: % of relays is ok

Refactor the Broadcast use case into several concerns.

• cache with state information

    PriorityBroadcast: 0
    PolicyBroadcast: all ok
    PolicyEviction: replace
    event1: broadcast: {
       relay 1 ok
       relay 2 failed, timeout
    }

• cache of deleted events
• Broadcast monitor (checks for broadcast state, delegates work, runs periodically)
• broadcast (stateless, broadcasts and returns results with comprehensive err handeling)

To model the constraints on each event, we are implementing a BroadcastPolicy, EvictionPolicy and priority broadcast. Depending on the use case, an event must be accepted by one or multiple relays or just be accepted by a few.
These policies are checked and executed by the broadcast monitor depending on the current conditions.

Broadcast just executes a given policy/strategy given by the broadcast monitor and reports back.

BroadcastPolicys

• consider done %
• all ok
• todo

EvictionPolicys

• todo

Consequences

The main difficulty is the remote signer setup. As a workaround, we store unsigned events in cache (so they are queriable) and check with the broadcast monitor whether we can sign them before broadcasting.

Impact Radius

Accounts: edit, set up acc

Blossom/Files: publish blossom servers

Cashu: Not impacted rn

Connectivity: Not impacted

Domain verification: Not impacted

Follows: edit, setup

Gift Wrap publish

Lists: publish, edit

Metadata: publish, edit

Nwc: rpc method, offline zaps?

Relay sets publish, edit

Requests: Not impacted

User relay lists publish, edit

Wallets not impacted

Zaps offline zap? (how to get invoice)

Alternative proposals

Monolithc archetecture with a broadcast manager that encapsulates most of the retry logic attached to a state/cache class.

Final Notes

Proposal Accepted. https://github.com/relaystr/ndk/pull/679