## Snapchain Migration Guide

Snapchain is designed to be a drop-in replacement for [Hubble](https://github.com/farcasterxyz/hub-monorepo). To migrate, follow these steps:

1. Set up a Snapchain node ( [instructions](https://docs.neynar.com/snapchain/guides/running-a-node)).
2. Update your app to use `hub-nodejs` with a version `>=0.13.0`
3. Update the connection url to talk the new snapchain host and port.

## Notable differences

1. Ports have changed. The HTTP port is `3381` and gRPC is `3383`.
2. `submitMessage` has a slightly different API and semantics, detailed below.
3. `HubEvent` ids no longer contain timestamps and calling `extractEventTimestamp` may return invalid data.
4. When calling `subscribe` or using shuttle, note that there are only 2 shards on snapchain and they are 1 indexed (shard 0 is chain metadata and does not have user data)
5. `hub-web` is not fully supported and may not work in some cases.

### submitMessage

Messages once submitted must be included in blocks, similar to blockchain transactions. The `submitMessage` has two main differences from Hubble:

1. `submitMessage` requests must all contain `dataBytes` for Snapchain. The `hub-nodejs` builders handle this in all versions `>=0.13.0`, but if you’re not using those you will need to manually update this like so:

```javascript
   if (message.dataBytes === undefined) {
          message.dataBytes = protobufs.MessageData.encode(message.data).finish();
          message.data = undefined;
   }
   ```

2. `submitMessage` is best-effort. It’s possible, but rare, that `submitMessage` succeeds but the submitted message fails to get included in a block.