Description

The FallbackClient is designed to automatically switch to an alternative L1 endpoint when the current one encounters issues, and revert back once the primary endpoint is functional again.

The core logic operates as follows: When an error occurs, it is recorded until either the error count surpasses a predetermined threshold or the count is reset by a timer that executes once per minute. If the threshold is exceeded within a one-minute span, it suggests the L1 endpoint has become unreliable, prompting the system to select the next address in the L1 URL. A new RPC client is then created to replace the current one. Simultaneously, a separate Goroutine monitors the initial endpoint's health and, when deemed stable, reverts back to its use.

As the clients employed in op-node and op-batcher/op-proposer differ significantly, two distinct fallbackClients have been implemented. The op-node version incorporates additional features such as subscription management and RPC legality checks, resulting in a more complex implementation.

Rationale

We need to improve stability. Currently, the L1 endpoint is the most unstable point.

Example

Example of l1 flag after code modification:

--l1=https://data-seed-prebsc-1-s1.binance.org:8545,https://data-seed-prebsc-2-s2.binance.org:8545,https://data-seed-prebsc-2-s3.binance.org:8545

Changes

• Add fallback client code
• Implant fallback client in op-node, op-batcher, op-proposer related code