Gas Suggestion API overview

The EIP-1559 Gas Suggestion API is applicable to all EIP-1559-compatible EVM chains. It provides real-time gas price estimations based on network conditions. The response consists of two key components:

1. Base Fee Per Gas
2. Suggestion Tiers, which include:
   • Max Priority Fee Per Gas (also known as miner_tip)
   • Max Fee Per Gas (also referred to as effective gas price)

This document is specifically tailored for Ronin network. On other EIP-1559 chains, the default settings / fallbacks might be different.

Base Fee Per Gas

• Represents the portion of gas fees that will be burned by the network.
• It is not received by validators.
• On the Ronin chain (post-hardfork), the default base_fee_per_gas is 1 GWEI. Any transaction with a lower gas price will be dropped.
• The API calculates the base fee using the average base fee from the 20 most recent blocks, defaulting to 1 GWEI if the calculated value is lower.
• The API buffers this value by multiplying it by 2, following the Ethers v6 implementation.

Pseudo Code for Calculation:

base_fee_per_gas = max(1_000_000_000, avg_20_recent_block_base_fee) * 2

Max Priority Fee Per Gas (Miner Tip)

• This is the portion of the gas fee given to the block validator.
• On the Ronin chain (post-hardfork), the default priority_fee_per_gas is 20 GWEI. Any transaction below this threshold will be dropped.
• The miner tip is determined by averaging the miner tips from the 20 most recent blocks. If the calculated value falls below 20 GWEI, it defaults to 20 GWEI.

Pseudo Code for Calculation:

max_priority_fee_per_gas = max(20_000_000_000, avg_20_recent_miner_tip)

Max Fee Per Gas (Effective Gas Price)

• Calculated as the sum of max_priority_fee_per_gas and base_fee_per_gas.
• This represents the total gas price for a transaction.

Pseudo Code for Calculation:

max_fee_per_gas = max_priority_fee_per_gas + base_fee_per_gas

Calculation Process

The Gas Suggestion API uses eth_feeHistory to estimate gas prices:

RPC Call Example:

curl --location 'https://saigon-testnet.roninchain.com/rpc' \
--header 'Content-Type: application/json' \
--data '{
    "method": "eth_feeHistory",
    "params": [
        20, //the number of current blocks 
        "latest",
        [
            60 // fee_history_reward_percentiles
        ]
    ],
    "id": 1,
    "jsonrpc": "2.0"
}'

Expected Response Model:

type FeeHistory struct {
    OldestBlock  *big.Int     // First block in response
    Reward       [][]*big.Int // Priority fees per transaction per block
    BaseFee      []*big.Int   // Base fees per block
    GasUsedRatio []float64    // Gas usage ratio per block
}

• The length of Reward corresponds to the length of fee_history_reward_percentiles. In this case, [60] is used.
• The average base_fee_per_gas is calculated using the BaseFee list.
• The base_fee_per_gas is then buffered by multiplying it by 2, applicable to both medium and high tiers.
• The medium tier max_priority_fee_per_gas is derived from Reward[0] (since fee_history_reward_percentiles contains a single value).
• The high tier max_priority_fee_per_gas is determined by multiplying the medium-tier value by 1.2 (default buffer index).
• For each tier, max_fee_per_gas is calculated by summing base_fee_per_gas and max_priority_fee_per_gas.

Gas suggestion Response Model:

{
    "chain_name": "ronin-testnet",
    "type": "eip-1559",
    "base_fee_per_gas": "2000000000",
    "medium": {
        "max_priority_fee_per_gas": "20000000000",
        "max_fee_per_gas": "22000000000"
    },
    "high": {
        "max_priority_fee_per_gas": "24000000000",
        "max_fee_per_gas": "26000000000"
    }
}

Caveats

• The high-tier miner tip is calculated as medium_tier_miner_tip * 1.2. However, if network congestion is extreme or gas price distribution is uneven, this approach may fail.
• A possible alternative is increasing the number of items in fee_history_reward_percentiles, e.g., using [60, 100].
• In such an implementation, Reward[0] contains the medium-tier miner tips, while Reward[1] contains the high-tier ones.
• However, this approach is rarely necessary in production, as the Ronin network has not experienced chain hangs or heavy congestion. Additionally, users can manually set their own gas prices.

Alternative RPC Call Example:

curl --location 'https://saigon-testnet.roninchain.com/rpc' \
--header 'Content-Type: application/json' \
--data '{
    "method": "eth_feeHistory",
    "params": [
        20,
        "latest",
        [60, 100]
    ],
    "id": 1,
    "jsonrpc": "2.0"
}'