Websocket Proxy support for HA sequencers

[paranoiacblack]

Currently, the websocket proxy is designed to accept a single connection to an OP Stack sequencer running rollup-boost. Some chains like Unichain have an high-availability setup for their sequencers where there is one active sequencer and a set of candidate sequencers. Ideally, there would be one websocket proxy running that can support a set of connections to an OP Stack sequencer running rollup-boost rather than needing a websocket proxy per sequencer.

[danyalprout]

You can set multiple values for upstream_ws (ref), each value can be one builder.

We ran this on Base mainnet a few weeks ago and it mostly worked. The builder + websocket proxy don't currently respect pings + pongs so you get lots of disconnections from the non-active builders. Planning to take a look into adding support for this over the next few days