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Experimental features from RSKj

Below you can find all the experimental features released with RSKj. The experimental features are not enabled by default, and you need to explicitly enable them in your configuration file. These are features that are still being tested and may not be fully stable, we decide to release them so the community can start to use it and provide feedback about it. So we can also validate, improve and iterate on them before they are released as stable features in the future.

You will also find the version and height in which they were introduced, there are instructions on how you can configure, customize and start using them.

Snapshot Sync

TL;DR Snapshot Sync is an experimental feature that allows RSKj nodes to synchronize using a snapshot of the state of the blockchain, rather than downloading the whole blocks starting from genesis. This can significantly reduce the time it takes to synchronize a node, especially for large blockchains.

When was it released?

Snapshot Sync was released in RSKj version LOVELL-7.1.0, if you are using a version higher than this, you can enable and use this feature.

Full Long Sync is the standard method for getting a new RSKj node to match up with the existing blockchain network. The goal is to make sure the new node downloads and checks every transaction, contract, and block, starting from the very first one. This approach uses up quite a bit of time and computer resources.

Snapshot Sync is designed to make the sync process faster but still safe: Instead of getting the full blockchain history, state data is downloaded up to a certain point where there's enough information to rebuild the whole state quickly.

The main goal of Snapshot Sync is to have a new RSKj node ready to use in a shorter time in comparison to using the default Full Long Sync method.

How to Configure Snap-Capable Nodes

Nodes can be configured as Snap servers and/or clients by adding a new snapshot config block to the sync configurations.

Snap Server

A node can be configured as a Snap Server by adding the following to the sync configuration block:

snapshot = {
	server = {
		enabled = <bool>
	}
}

Snap Client

Snap client configurations must also be added to the sync configuration block, they allows for many options to be tweaked:

snapshot = {
	client = {
		enabled = <bool>
		checkHistoricalHeaders = <bool>
		parallel = <bool>
		chunkSize = <chunkSize>
		limit = <limit>
		snapBootNodes = [
			{
				nodeId = <id>
				ip = <ip>
				port = <port>
			}
		]
	}
}

⚠️ Important Notes

The minimal sync configuration for Snap Sync MUST include the enabled property set to true beside the node being configured as a Snap-Capable server or client, like this:

sync {
	enabled = true
	<SNAP_SYNC_CONF>
}

There's an extra option added to peer configuration section that can be used to further tweak the Snap Sync process:

peer {
	...
	messageQueue {
		...
		# Reject peer's messages over this threshold
    # It's calculated using exponential moving average
		thresholdPerMinutePerPeer = <int>
	}
}

The RskCli tool accepts two options regarding Snap Sync:

--sync-mode can be used to set the synchronization mode. It accepts one string containing full or snap as values.

--snap-nodes can be used to set a list of Snap-Capable peers to connect to. It accepts a string list of nodes in the format enode://PUBKEY@HOST:PORT

Monitoring

In order to know if the process is working, snapshotprocessor logs may be filtered out by executing tail -f /path/to/rsk/logs/rsk.log | grep “snapshotprocessor”, log messages will be different depending on the node being a Snap server or client.

Snap Server Logs

The first snapshotprocessor related log line will appear once a client start asking for Snap messages, and looks like this:

2025-04-01-01:22:00.195 DEBUG [snapshotprocessor]  Processing snapshot status request, checkpointBlockNumber: 220000, bestBlockNumber: 221583

And then, messages like these are going to be repeated until there's no more clients asking for messages:

2025-04-01-01:27:39.793 DEBUG [snapshotprocessor]  Processing state chunk request from node NodeID{9d8946b40c529eb77602704a63fe8c9b072e633f2b3025bfeb3593d691a2d797e4eb4a4cc3665dcb2ebc58a208e5c96b1370c05204d6e56ab96c4a99ddaee87b}. From 54425600 to calculated 54476800 being chunksize 50
2025-04-01-01:27:39.793 DEBUG [snapshotprocessor]  Sending state chunk from 54425600 to 54476800
2025-04-01-01:27:39.805 DEBUG [snapshotprocessor]  Sending state chunk from 54425600 of 56935 bytes to node NodeID{9d8946b40c529eb77602704a63fe8c9b072e633f2b3025bfeb3593d691a2d797e4eb4a4cc3665dcb2ebc58a208e5c96b1370c05204d6e56ab96c4a99ddaee87b}, totalTime 12ms
2025-04-01-01:27:39.823 DEBUG [snapshotprocessor]  Processing state chunk request from node NodeID{9d8946b40c529eb77602704a63fe8c9b072e633f2b3025bfeb3593d691a2d797e4eb4a4cc3665dcb2ebc58a208e5c96b1370c05204d6e56ab96c4a99ddaee87b}. From 54476800 to calculated 54528000 being chunksize 50
2025-04-01-01:27:39.823 DEBUG [snapshotprocessor]  Sending state chunk from 54476800 to 54528000
2025-04-01-01:27:39.844 DEBUG [snapshotprocessor]  Sending state chunk from 54476800 of 62776 bytes to node NodeID{9d8946b40c529eb77602704a63fe8c9b072e633f2b3025bfeb3593d691a2d797e4eb4a4cc3665dcb2ebc58a208e5c96b1370c05204d6e56ab96c4a99ddaee87b}, totalTime 21ms
2025-04-01-01:27:39.867 DEBUG [snapshotprocessor]  Processing state chunk request from node...

Snap Client Logs

In the Snap client side, the first Snapshotprocessor related line will look like this:

2025-04-01-01:22:00.179 INFO [snapshotprocessor]  Starting Snap sync

Followed by a stream of messages similar to these:

2025-04-01-01:22:02.341 DEBUG [snapshotprocessor]  Processing snap blocks response. Receiving from block 217600 to block 217999 Objective: 214000.
2025-04-01-01:22:02.584 DEBUG [snapshotprocessor]  SnapBlock - nexChunk : 217600 - lastRequired 214000, missing 3600
2025-04-01-01:22:02.585 DEBUG [snapshotprocessor]  Sending request: [SNAP_BLOCKS_REQUEST_MESSAGE] with id: [7] to: [NodeID{cb3db6d3187550a304b16329b9dfcf15abf0d5aa817d28ea0a0f4547b7eefdc1badb38e800db276ae2a6aa2bb81fbf4459606d10d3aad7be4934a748ecd9fae8}]
2025-04-01-01:22:02.711 DEBUG [snapshotprocessor]  Processing snap blocks response. Receiving from block 217200 to block 217599 Objective: 214000.
2025-04-01-01:22:02.915 DEBUG [snapshotprocessor]  SnapBlock - nexChunk : 217200 - lastRequired 214000, missing 3200
2025-04-01-01:22:02.915 DEBUG [snapshotprocessor]  Sending request: [SNAP_BLOCKS_REQUEST_MESSAGE] with id: [8] to: [NodeID{cb3db6d3187550a304b16329b9dfcf15abf0d5aa817d28ea0a0f4547b7eefdc1badb38e800db276ae2a6aa2bb81fbf4459606d10d3aad7be4934a748ecd9fae8}]
...

Until the whole process ends, and the following logs will look something like these:

2025-04-01-01:27:39.975 INFO [snapshotprocessor]  Recovering trie...
2025-04-01-01:27:41.879 INFO [snapshotprocessor]  State final validation OK!
2025-04-01-01:27:42.437 INFO [snapshotprocessor]  Setting last block as best block...
2025-04-01-01:27:42.437 INFO [snapshotprocessor]  Snap sync finished successfully

Fiat Stable MinGasPrice

In the context of RSKj and cryptocurrency, Fiat Stable MinGasPrice usually refers to a way of stabilizing the minimum gas price based on the value of a fiat currency (like USD, EUR, etc.).

When was it released?

Fiat Stable MinGasPrice was released in RSKj version LOVELL-7.1.0, if you are using a version higher than this, you can enable and use this feature.

Important Definitions:

Gas Price: In RSKj, when you send a transaction or interact with a smart contract, you pay a gas fee to the network. The gas price is how much you pay per unit of gas.
Fiat Stable: This suggests trying to peg (or stabilize) the minimum gas price to a fixed value in fiat currency, even though RSKj's currency (RBTC) is volatile.
MinGasPrice: This would be the minimum allowed gas price — the lowest cost you can set for your transaction to be accepted or processed.

How it works:

Fiat Stable MinGasPrice means setting a minimum gas price that, no matter how much RBTC's price goes up or down, tries to represent a fixed real-world value (like "always costing about 0.01 USD worth of gas minimum").

Why does it matter?

If RBTC price suddenly spikes, gas fees could become ridiculously high in dollar terms.
By using a fiat-stable minimum, systems can ensure fair and predictable pricing for users and maintain network security and validator incentives.

Motivation and context for the changes

Currently, RSK miners can set the minimum gas price (MinGasPrice) using the miner.minGasPrice configuration, which is denominated in WEI and inherently linked to the Bitcoin price. This linkage causes transaction costs to fluctuate with Bitcoin's value, potentially leading to increased costs when Bitcoin appreciates, thereby adversely affecting user experience.

To address this issue, the proposed feature aims to empower miners with the ability to specify and configure the minimum gas price in fiat currency. This change would stabilize transaction costs in fiat terms, regardless of cryptocurrency market variations, and is intended to enhance predictability and user satisfaction. The system used to support only one configuration parameter for setting the MinGasPrice. See an example here:

miner {
	# The default gas price
	minGasPrice = 60000000
	server.enabled = true
	
	client {
	    enabled = true
	    delayBetweenBlocks = 0 seconds
	    delayBetweenRefreshes = 1 seconds
	}
	
	coinbase.secret = regtest_miner_secret_please_change
	
	stableGasPrice {
	    enabled = true
	
	    source {
	         method = "ETH_CALL"
	         params {
	            from = "0x0000000000000000000000000000000000000000"
	            to = "0xCA41630b09048b6f576459C34341cAB8Dc2cBE7E"
	            data = "0xdf16e52d"
	         }
	    }
	
	    minStableGasPrice = 476190000000 # 0.00000426528 USD per gas unit
	
	    # # The time the miner client will wait to refresh price from the source.
	    # # Value's type is `Duration`, e.g. 1.1 seconds, 2.5 minutes, 3 hours, 4 days.
	    refreshRate = 10 minutes
	}
}

The goal is to give miners a capability to specify / configure min gas price value denominated in a fiat currency.

PR that added the changes

https://github.com/rsksmart/rskj/pull/2310

🔗 HTTP Call (Off-Chain Method)

This approach uses a centralized or semi-centralized API to fetch the current RBTC-to-fiat price and then calculate a gas price based on that.

How it works:

The system (like a wallet, dApp backend, or node) sends an HTTP request to a price oracle or API like:
- CoinGecko
- Chainlink's external adapters
- Custom backend service
It retrieves the current RBTC/USD price, then calculates: minGasPrice = fiatMinPrice / ethPrice
Example: If you want the gas price to represent $0.01, and RBTC = $2000, then: minGasPrice = 0.01 / 2000 = 0.000005 RBTC (or 5 gwei)

✅ Pros:

Simple, flexible, easy to integrate.
Can pull from a wide range of data sources.

❌ Cons:

Centralization risk – you're trusting the HTTP source.
Not trustless – the blockchain doesn't verify the result.
Latency and reliability – dependent on network and endpoint availability.

⛓️ On-Chain Oracle Call (Decentralized/Trustless Method)

This approach fetches the RBTC-to-fiat price from a smart contract, often powered by a decentralized oracle network like Chainlink.

How it works:

Smart contracts call an on-chain oracle (e.g., Chainlink RBTC/USD price feed).
The gas price is derived using the oracle's latest reported price.
This is done inside smart contracts, ensuring consistency and trust.

✅ Pros:

Trustless and secure – all nodes agree on the same value.
Tamper-resistant – oracle data is resistant to manipulation.
Fully on-chain – compatible with DeFi, DAO governance, etc.

❌ Cons:

Gas cost – reading from an oracle contract uses gas.
Oracle update frequency – price may not always be up to the second.
Complexity – needs integration with oracle networks and possibly fallback logic.

Summary Table:

Method	Trust Level	Cost	Speed	Use Case
HTTP API (Off-chain)	Centralized	Low	Fast	Backend services, UI, analytics
On-chain Oracle	Decentralized	Moderate	Near real-time	Smart contracts, DeFi, DAOs

RSK Configuration

Miner configurations depends on the desired method used to request the min gas price. An example miner configuration can be seen here

HTTP CALL

Configurations for using HTTP to request the min gas price

miner {
    stableGasPrice {
        enabled = false

        source {
	        # method options: HTTP_GET | ETH_CALL
            # Examples:
            method = "HTTP_GET"
            params {
                url = "https://api.coingecko.com/api/v3/simple/price?ids=ethereum&vs_currencies=usd"
                # response: {"ethereum":{"usd":1848.79}}
                jsonPath = "ethereum/usd"
                timeout = 2 seconds # Value's type is `Duration`, e.g. 1.1 seconds, 2.5 minutes, 3 hours, 4 days.
            }
        }
				
        minStableGasPrice = 4265280000000 # 0.00000426528 USD per gas unit
        # The time the miner client will wait to refresh price from the source.
        # Value's type is `Duration`, e.g. 1.1 seconds, 2.5 minutes, 3 hours, 4 days.
        refreshRate = 6 hours
    }
}

Parameters for the source:

method: will choose the way of getting the min gas price, in this case through HTTP CALL.
url: is the HTTP url that will be used to get the min gas price.
jsonPath: assuming the response type we get from the API is JSON, this is the path to extract the information from the JSON response.
timeout: wait time to get the response. If the response takes longer than the amount set, an exception will be thrown.

ETH CALL

Configurations for using ETH CALL to request the min gas price

miner {
    stableGasPrice {
        enabled = false

        source {
             method = "ETH_CALL"
             params {
                from: "0xcd2a3d9f938e13cd947ec05abc7fe734df8dd825",
                to: "0xcd2a3d9f938e13cd947ec05abc7fe734df8dd826",
                data: "0x8300df49"
             }
        }

        minStableGasPrice = 4265280000000 # 0.00000426528 USD per gas unit
        # The time the miner client will wait to refresh price from the source.
        # Value's type is `Duration`, e.g. 1.1 seconds, 2.5 minutes, 3 hours, 4 days.
        refreshRate = 6 hours
    }
}

Parameters for the source:

method: will choose the way of getting the min gas price, in this case through ETH CALL, using the smart contracts.
from: technically not required by the EVM to read state, but it's needed for:
- Contextual computation: Some smart contracts behave differently based on the caller (msg.sender)
- Simulating gas costs: eth_call can simulate how much gas a given sender would need.
- Fallback behavior: Some contracts restrict who can call them.
to: is required because you're calling a specific smart contract. Without to, RSKj wouldn’t know which contract to interact with.
data: this is the function that we want to call from the contract.

Experimental features from RSKj

Snapshot Sync

When was it released?

How to Configure Snap-Capable Nodes

Snap Server

Snap Client

⚠️ Important Notes

Monitoring

Snap Server Logs

Snap Client Logs

Fiat Stable MinGasPrice

When was it released?

Why does it matter?

Motivation and context for the changes

PR that added the changes

🔗 HTTP Call (Off-Chain Method)

How it works:

✅ Pros:

❌ Cons:

⛓️ On-Chain Oracle Call (Decentralized/Trustless Method)

How it works:

✅ Pros:

❌ Cons:

Summary Table:

RSK Configuration

On this page

More

Feedback

Snapshot Sync​

When was it released?​

How to Configure Snap-Capable Nodes​

Snap Server​

Snap Client​

⚠️ Important Notes​

Snap-Related RSKCli Tool Options​

Monitoring​

Snap Server Logs​

Snap Client Logs​

Fiat Stable MinGasPrice​

When was it released?​

Why does it matter?​

Motivation and context for the changes​

PR that added the changes​

🔗 HTTP Call (Off-Chain Method)​

How it works:​

✅ Pros:​

❌ Cons:​

⛓️ On-Chain Oracle Call (Decentralized/Trustless Method)​

How it works:​

✅ Pros:​

❌ Cons:​

Summary Table:​

RSK Configuration​

On this page

More

Feedback

Snapshot Sync

When was it released?

How to Configure Snap-Capable Nodes

Snap Server

Snap Client

⚠️ Important Notes

Snap-Related RSKCli Tool Options

Monitoring

Snap Server Logs

Snap Client Logs

Fiat Stable MinGasPrice

When was it released?

Why does it matter?

Motivation and context for the changes

PR that added the changes

🔗 HTTP Call (Off-Chain Method)

How it works:

✅ Pros:

❌ Cons:

⛓️ On-Chain Oracle Call (Decentralized/Trustless Method)

How it works:

✅ Pros:

❌ Cons:

Summary Table:

RSK Configuration