Evm can't be sent between threads

[impactdni2]

Working on 4.0 support in my application, and trying to figure out what the correct pattern is for passing an Evm to a thread.

My use case is I have an Evm that has been built (DB, BlockEnv, etc), and I'd like to simulate multiple parallel transactions (with different inputs) in that environment.

My previous (pseudo)code was:

fn simulate(evm: EVM) {
  some_list
    .par_iter()  // <-- rayon parallelization
    .for_each(|item| {
      let mut evm = evm.clone();
      // modify evm transaction env
      // simulate txn
    });
}

Looks like in 4.0, Evm can't be safely sent between threads. Is there any recommended way to accomplish this? Should I just be pulling out the DB + Env, and sending those to the thread and rebuilding a new Evm?

[impactdni2]

Am I correct in assuming that what I previously had as an EVM being passed around, is now better represented as just a DB + Env? And then build a new Evm from those when needed?

[rakita]

I would say: DB+ Env+ SpecId(HandlerCfg).

Maybe we should add function with_context_with_handler_cfg() to EvmBuilder and allow those to be extracted from evm (something like evm.into_context_with_handler_cfg().

I would try to specify the Emv<'static,..> this could potentially work. nope, problem is with Handler Boxes that are not marked as Send. so without Handler, this would work.

[rakita]

Added into_context_with_handler_cfg this would get you struct that can be send

And you can recreate Evm with EvmBuilder and with that struct

[rakita]

This PR: #1068

[impactdni2]

This looks perfect. Really appreciate all your hard work on revm :)

[rakita]

Closing this, new version released.