feat(iota-graphql-rpc): add subscription recovery

[sergiupopescu199]

Description of change

This PR adds subscription recovery support to iota-graphql-rpc, allowing clients to resume transaction and event subscriptions from a specific transaction digest after a disconnection.

When a startFrom digest is provided, the stream first backfills historical data from the database, then seamlessly transitions to live data from the broadcast channel. Without startFrom, behavior is unchanged.

Links to any relevant issues

fixes #11199

How the change has been tested

• started a local network using the iota-localnet

cargo r --features indexer  -- start --force-regenesis --with-indexer --with-graphql

• First started a grpahql subscription through the grpahiql on http://localhost:9125

subscription Transactions {
    transactions {
        __typename
        ... on TransactionBlock {
            digest,
           effects {
            checkpoint {
              sequenceNumber,
            }
          }
        }
        ... on Lagged {
            count
        }
    }
}

• Stopped the subscription and got the latest digest it returned. Used that digest to start a new subscription.

subscription Transactions {
    transactions(startFrom: "5GJHkPzZq94pn74q5Mfd1GtZPC6TXNFN8a2sXYoEVkkd") {
        __typename
        ... on TransactionBlock {
            digest,
           effects {
            checkpoint {
              sequenceNumber,
            }
          }
        }
        ... on Lagged {
            count
        }
    }
}

• The client received historical transactions noticeably faster than live ones. Historical data is fetched from the database in batches, limited only by query speed. Live data depends on the network's checkpoint production rate, which is inherently slower. The debug logs confirmed the transition from historical backfill to live streaming.

• Basic tests (linting, compilation, formatting, unit/integration tests)

• Patch-specific tests (correctness, functionality coverage)

Infrastructure QA (only required for crates that are maintained by @iotaledger/infrastructure)

• Synchronization of the indexer from genesis for a network including migration objects.
• Restart of indexer synchronization locally without resetting the database.
• Restart of indexer synchronization on a production-like database.
• Deployment of services using Docker.
• Verification of API backward compatibility.

Release Notes

• GraphQL: Subscription queries now accept an optional startFrom transaction digest to resume receiving transactions and events from a specific point.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

6 Skipped Deployments

Project	Deployment	Actions	Updated (UTC)
apps-backend	Ignored		Apr 9, 2026 8:38am
apps-ui-kit	Ignored		Apr 9, 2026 8:38am
iota-evm-bridge	Ignored		Apr 9, 2026 8:38am
iota-multisig-toolkit	Ignored		Apr 9, 2026 8:38am
rebased-explorer	Ignored		Apr 9, 2026 8:38am
wallet-dashboard	Ignored		Apr 9, 2026 8:38am