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State Sync keeps your environment in real-time sync with the state of the parent network. This helps ensure you can access all blocks produced after the Virtual Environment has been created.
State Sync is available on the paid plan. To enable it for your account, contact our sales team.
You enable State Sync when creating the Virtual Environment, by selecting the State only sync network sync mode. The sync mode cannot be changed after creation; to use a different mode, create a new Virtual Environment.
Need block-for-block alignment with the parent network and a visible mempool? See Network Mirror Mode, it’s a stronger guarantee than State Sync, with time controls and a state-drift lens for comparing your Virtual Environment against mainnet.
Behavior of mainnet contracts that cache block.number is unpredictable when running Virtual Environment transactions, since the block number grows at different rates on mainnet and Virtual Environment.

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When to activate State Sync

This option is useful in several scenarios:
  • Virtual Environment contracts and transactions can access current Oracle values that are present on the original chain.
  • Access Uniswap pools from the Virtual Environments when testing contracts and building proof-of-concept transactions.
  • Build a subgraph without stale data.
  • Test the behavior and performance of your dapps and protocols in one-to-one correspondence with real network conditions

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How State Sync resolves write collisions

State sync enables you to access the latest values of storage slots and account balances on mainnet as they update. Upon writing to a particular storage slot on the Virtual Environment, synchronization stops for that slot, but remains active for all unmodified ones. Here’s state sync in more detail:
  • The initial block number matches the latest block of the original chain at the time of creation.
  • Each time you send a transaction to a Virtual Environment via eth_sendRawTransaction and eth_sendRawTransaction, a block is minded and block number increases by 1, independently of the original network.
  • Until writing to a variable on Virtual Environment, the Virtual Environment tracks the current value from the original network.
  • After writing to a variable on Virtual Environment of a contract (e.g., C.X=100), any subsequent read will yield that value (100).
  • All unmodified state variables of a contract (C.Y) will reflect the value from the original network.
  • Before a new block is mined on a Virtual Environment, the latest virtual block is synchronized with the latest block on the parent chain.
  • Virtual Environment mines a block after every state modification (sendTransaction, setBalance, etc.).
  • Block numbers on Virtual Environment and the original network will change with different rates.
For better understanding, let’s explore an example:

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Example

The example demonstrates the following:
  • Virtual Environment (Virtual Sepolia) accesses the latest state from original network (Sepolia).
  • After a Virtual Environment write, the modified variable detaches from its Sepolia counterpart.
You can find the example on Github:

State Sync Example

Th example uses a modified Counter contract, that contains a map of counters. It’s deployed on Sepolia at 0xd01dF6d2354c5A869265dC9a9561E3544ac53262. The test script will interact with both Sepolia and a Virtual Environment based on Sepolia - Virtual Sepolia. The script takes a random entry in the counter map, and then:
  • Sets the value on Sepolia, then reads values on both Sepolia and Virtual Sepolia, showing that the same value is read back.
  • Sets the value on Virtual Sepolia, then reads values on both Sepolia and Virtual Sepolia, showing that different values are read.
  • Again sets the value on Sepolia, then reads values on both Sepolia and Virtual Sepolia, showing that the modification on Sepolia is invisible on its virtual counterpart.
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Create a Virtual Environment
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Create a new Virtual Environment based on Sepolia, using 735711155111 as the custom Chain ID.
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Environment setup
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Copy .example.env template and replace the following:
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  • TENDERLY_VIRTUAL_TESTNET_CHAIN_ID the chain ID of the Virtual Environment. Use 735711155111
  • TENDERLY_VIRTUAL_TESTNET_RPC_URL_SEPOLIA the RPC URL of the Virtual Environment
  • PRIVATE_KEY for signing test transactions
    • 6
    cp .example.env .env
vi .env # modify environment variables
    7
    cd virtual-environments-state-sync
source .env
yarn install
npx ts-node src/index.ts
    8
    Results
    9
    Key points to notice about write operations:
    10
  • After writing to sepolia (1), both sepolia and virtualSepolia read value 1 - the latest state of the original network.
  • After writing to Virtual Sepolia (10), reading from Sepolia gives the previously set value (1), and reading from virtualSepolia gives the recently set value (10).
  • After writing to Sepolia again (100), reading from Sepolia gives the latest set value (100), and reading from virtualSepolia gives the previously set value (10).
    • 11
    Playing with Counter(0xd01dF6d2354c5A869265dC9a9561E3544ac53262).numbers[3788720642447205]
State:
  sepolia: 0
  virtualSepolia: 0

================================================================================================
Write: Counter(0xd01dF6d2354c5A869265dC9a9561E3544ac53262)@Sepolia.numbers[3788720642447205] = 1
Tx hash: 0xe57c5da70c68d55f86957f7a2fc2644670b032fe5f972b9e9ccc2774cd2ba352
State:
  sepolia: 1
  virtualSepolia: 1

================================================================================================
Write: Counter(0xd01dF6d2354c5A869265dC9a9561E3544ac53262)@Virtual Sepolia.numbers[3788720642447205] = 10
Tx hash: 0x56099d89c1d6fd001a1e9a0cecca13e13c04013b473acb6a48cd61a4b988696c
State:
  sepolia: 1
  virtualSepolia: 10

================================================================================================
Write: Counter(0xd01dF6d2354c5A869265dC9a9561E3544ac53262)@Sepolia.numbers[3788720642447205] = 100
Tx hash: 0xc3c37e912bfa4fca9b980339fa2c95dbef75d6c605f0df831ca985b0ef3b61ec
State:
  sepolia: 100
  virtualSepolia: 10