Dynamic Node Configuration

The feature is accessed via the --config-changes flag when running marood testnet. The value is a string containing one or more overrides. Multiple overrides are separated by commas.

Syntax: "path.to.key=value,another.key=value"

• Nested Keys: Use dot notation for nested fields (e.g., consensus.timeout_commit=1s).
• Top-Level Keys: Use the key directly for top-level fields (e.g., log_level="debug").
• String Slices: For fields that accept a list of strings, provide a comma-separated list within the value (e.g., p2p.persistent_peers="id1@host1:port1,id2@host2:port2").

To create a testnet where the commit timeout is reduced to 1 second and the log level is set to debug, you would use the following flag:

marood testnet -v 2 --config-changes "consensus.timeout_commit=1s,log_level=debug"

This will apply these changes to the config.toml file of every node generated by the command.

The testnet_utils.go file contains the logic for this feature. It parses the string provided to the flag, splitting it by commas into individual overrides. For each override, it splits the key and value at the = sign. It then uses reflection to traverse the CometBFT Config struct, locate the target field based on its mapstructure tag or name, and set its value. The utility supports various data types, including strings, booleans, integers, and time.Duration, automatically parsing the value string into the correct type.

This feature is particularly useful for:

• Stress Testing: Drastically reducing block times (consensus.timeout_commit) to test network performance under high load.
• Debugging: Increasing log verbosity (log_level) to get more detailed output when troubleshooting issues.
• Simulating Network Conditions: Customizing P2P settings like max_num_inbound_peers or send_rate to simulate different network topologies or constraints.