[Bug] CachedNonceManager should not be Clone

[pmikolajczyk41]

Component

provider, pubsub

What version of Alloy are you on?

alloy-provider v0.4.2 (main branch)

Operating System

Linux

Describe the bug

Problem description

CachedNonceManager keeps DashMap for local storing of the current nonce per account. DashMap implements Clone (https://docs.rs/dashmap/latest/src/dashmap/lib.rs.html#96-110) by simply coping every entry. Therefore, two clones of a CachedNonceManager instance will fall into a conflict after just one transaction.

The right way of using it

As in the unit test (https://github.com/alloy-rs/alloy/blob/main/crates/provider/src/fillers/nonce.rs#L213-L214), any provider using nonce caching underneath MUST be kept under Arc. However, lib API doesn't enforce that and thus it is very easy (and pretty natural) to clone raw providers and counting that the nonce caching will be shared across clones.

If these clones share signer (e.g. WalletFiller), then a nonce conflict is inevitable (unless provider is always cloned before sending any transaction, but then we don't benefit from local caching, since the nonce is always being fetched).

General solution

IMHO the problem lies in the totally weird impl Clone for DashMap and thus I suggest two ways of keeping users safe:

1. change DashMap to anything reasonable, where cloning actually preserves entries
2. make CachedNonceManager !Clone

Reproduction of a very easy misuse

    #[tokio::test]
    async fn cloned_caching_does_not_cooperate() {
        let filler = NonceFiller::<CachedNonceManager>::default();
        let filler_copy = filler.clone();

        let provider = ProviderBuilder::new().on_anvil();
        let address = Address::ZERO;

        assert_eq!(
            filler.nonce_manager.get_next_nonce(&provider, address).await.unwrap(),
            0
        );
        assert_eq!(
            filler_copy.nonce_manager.get_next_nonce(&provider, address).await.unwrap(),
            1
        );
    }

[nadtech-hub]

🙋‍♂️