Configure Truffle to Connect to RSK: A Step-by-Step Guide

Understanding Truffle's default configuration values (based on Ethereum),
in particular surrounding polling intervals; and using 2 relatively new config options allows one to config Truffle to better connect to an RSK node.

Public Nodes

When connecting to public nodes, it is crucial to understand that you are interacting with the nodes indirectly. Each RPC request goes through a series of hops through other infrastructure, such as authentication gateways, load balancers, rate limiters, et cetera. Each of these other layers contains its own logic that may be more restrictive than the node itself.

You may opt to work around this by running your own node on

localhost

Ethereum Defaults

Truffle's default configuration is optimised for the Ethereum network.
However, some of these values are incompatible with the RSK network,
and need to be overridden accordingly. Remember that while RSK is compatible with Ethereum both at the RPC level and at the VM level; its internal implementation can be quite different.

The main difference lies in the relationship between block interval and polling interval.

The block interval is the duration of time between a block being added to the blockchain and the next one being added. Note that all transactions must be in a block in order to be added to the blockchain (AKA "has been mined").

RSK's block interval is currently approximately 30 seconds, whereas
Ethereum's block interval is currently approximately 15 seconds.

Client applications, such as decentralised applications, or in this case Truffle (a developer tool), need to periodically check if blocks, and therefore transactions, that have been submitted have since been added to the blockchain. The polling interval is the duration of time between
one such check and the next.

It thus makes sense to optimise the efficiency of the client application
by configuring a polling interval that is commensurate with the anticipated block interval. Drawing upon the concept of critical frequency (in Nyquist–Shannon sampling theorem), it makes sense to pick a 15 second polling interval when anticipating a 30 second block interval from RSK. Manual testing appears to indicate that this works well.

Note that Truffle's default is a 4 second polling for an anticipated 15 second block interval on Ethereum. This is still "allowed", as critical frequency as that specifies the upper bound of the sampling to be half. Configuration values should be picked carefully by weighing the pros and cons of performance against resource intensity.

Note that Truffle's implementation has 2 separate polling intervals:

one for
```
provider.pollingInterval
```
, which is for "regular" usage, and
another for
```
deploymentPollingInterval
```
, which is used exclusively for deployments (truffle migrate)

These configuration options were originally not implemented, and were set to hard coded defaults. These were added specifically top be able to support networks with a different block interval!

Configuring Truffle

With all the above in mind, let's now see how to implement this in a Truffle project.

In your

truffle-config.js

file:

(1) Set a variable

testnetSeedPhrase

to contain a valid BIP-39 mnemonic phrase

(2) Set a variable

gasPriceTestnet

to contain the gas price you wish to use denominated in Wei.

(3) In the exported

config

object, set the value of

config.networks.testnet

to be the following.

    testnet: {
      provider: () => new HDWalletProvider({
        mnemonic: {
          phrase: testnetSeedPhrase,
        },
        providerOrUrl: 'https://public-node.testnet.rsk.co/',
        // Higher polling interval to check for blocks less frequently
        pollingInterval: 15e3,
      }),
      // Ref: http://developers.rsk.co/rsk/architecture/account-based/#chainid
      network_id: 31,
      gasPrice: gasPriceTestnet,
      networkCheckTimeout: 1e6,
      timeoutBlocks: 100,
      // Higher polling interval to check for blocks less frequently
      // during deployment
      deploymentPollingInterval: 15e3,
    },

(4) Now you can run

truffle

sub-commands with this network selected,
for example:

truffle migrate --network testnet

That's it!