EVM Bytecode Execution / StateManager: How to keep progress? #2338
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Hi👋 Just a quick question, because I haven't seen examples in repo or in previous issues(or I was unattentive). Saying, we have an example like here: It's a good example to get started, but I can't understand how to save this progress of VM. Here, the code done execution and on the high level we have the next stuff in "blackbox"
So, what should I do to "save" this progress?What should I do to run the vm from some "checkpoint" next time to get the second variant of greeting? StateManager has no instructions in docs. Or maybe I should play with Thanks in advance for your reply) |
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Replies: 1 comment · 2 replies
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Hi, the key idea of this all is that to save the current state of the chain (so all accounts and contracts) is in a thing called the |
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Yes, marked as answer) Thanks for hint. For everyone who bumped with the same issue: Your should dig dive deeper. In my case, I've noticed that Later,when you need to start your VM from some "checkpoint", pass the root to Snippet import {DefaultStateManager} from '@ethereumjs/statemanager'
import {Trie} from '@ethereumjs/trie'
import {VM} from '@ethereumjs/vm'
import {Level} from 'level'
import LevelDB from '<YOUR_IMPLEMENTATION_PATH>' //you can use my version here https://gist.github.com/VladChernenko/e4fca3622aa4a7c0cd1885b91f7977ac
//Our your own options
const common = new Common({ chain: Chain.Rinkeby, hardfork: Hardfork.Istanbul })
const trie = new Trie({
db:new LevelDB(new Level('<YOUR DB>')),
useKeyHashing:true
})
const stateManager = new DefaultStateManager({trie})
const vm = await VM.create({ common,stateManager })
await vm.stateManager.setStateRoot(Buffer.from('<32-bytes hex root which your previously store>','hex'))
//__________________ Now you can get accounts/make contracts call from checkpoint__________________ |
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I think this would already be an example worth to be added to the Statemanager documentation, have added a respective issue #2356. |
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Hi, the key idea of this all is that to save the current state of the chain (so all accounts and contracts) is in a thing called the
stateRoot. You can think of this (high-level) as a cryptographic hash of the entire chain. To checkpoint or rollback, simply save thestateRoot(to get this, usestateRoot = await vm.stateManager.getRoot()) and if you want to rollback,await vm.stateManager.setRoot(stateRoot). If you wish to persist these changes on disk, you need to instantiate aStateManagerwith aLevelDBwhich saves to disk, and pass this along the VM constructor.