ChainSpec

Chain Specifications

The Chain Specification is a configuration that defines all core constants of the JAM Chain. While the chain itself has fixed parameters as defined in the Graypaper, alternative configurations can be useful for testing and local deployments.

Configuration Parameters

Each chain specification defines the following parameters (with shorthand identifiers):

• chain
  The name of the spec.

• num_validators (V)
  The number of validators.

• num_cores (C)
  The number of cores.

• slot_duration (P)
  Slot time duration in seconds.

• epoch_duration (E)
  The number of slots in an epoch.

• contest_duration (Y)
  The epoch in which the ticket contest ends.
  Constraint: Y > 0 and Y < E

• tickets_per_validator (N)
  The maximum number of tickets each validator can submit. This must be configurable to ensure that a 2/3+1 majority of validators can complete the ticket contest successfully.
  Constraint: ((2/3) * V + 1) * N >= E

• rotation_period (R)
  The rotation period of validator-core assignments, measured in timeslots.

• max_tickets_per_extrinsic (K)
  The maximum number of tickets which may be submitted in a single extrinsic.
  Constraint: K > 0

Predefined Configurations

The jam.chainspec module provides several preset configurations via the JamConfig class. These include:

• JamConfig.tiny()
• JamConfig.small()
• JamConfig.medium()
• JamConfig.large()
• JamConfig.xlarge()
• JamConfig.xlarge2()
• JamConfig.xlarge3()
• JamConfig.full()

You can obtain a configuration by calling JamConfig.from_chain(chain_name), where chain_name is one of the available specification names. The configuration is typically selected using the environment variable JAM_CHAIN_SPEC (defaulting to "tiny" if not specified).

Usage

from jam.chainspec import JamConfig

# Get the default configuration
config = JamConfig.from_chain("tiny")

# Access configuration parameters
print(f"Number of validators: {config.num_validators}")
print(f"Slot duration: {config.slot_duration} seconds")

# Use configuration in node setup
node = JamNode(config=config)