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).

JAM protocol configuration.

class jam.chainspec.ChainSpec(value, names=<not given>, *values, module=None, qualname=None, type=None, start=1, boundary=None)

Bases: Enum

Chain specification types.

TINY = 'tiny'

SMALL = 'small'

MEDIUM = 'medium'

LARGE = 'large'

XLARGE = 'xlarge'

XLARGE2 = '2xlarge'

XLARGE3 = '3xlarge'

FULL = 'full'

class jam.chainspec.JamConfig(chain: ChainSpec, num_validators: int, num_cores: int, slot_duration: int, epoch_duration: int, ticket_submission_end: int, contest_duration: int, tickets_per_validator: int, max_tickets_per_extrinsic: int, rotation_period: int | None)

Bases: object

JAM protocol configuration.

chain: ChainSpec

num_validators: int

num_cores: int

slot_duration: int

epoch_duration: int

ticket_submission_end: int

contest_duration: int

tickets_per_validator: int

max_tickets_per_extrinsic: int

rotation_period: int | None

classmethod tiny() → JamConfig

Create tiny chain configuration.

classmethod small() → JamConfig

Create small chain configuration.

classmethod medium() → JamConfig

Create medium chain configuration.

classmethod large() → JamConfig

Create large chain configuration.

classmethod xlarge() → JamConfig

Create xlarge chain configuration.

classmethod xlarge2() → JamConfig

Create 2xlarge chain configuration.

classmethod xlarge3() → JamConfig

Create 3xlarge chain configuration.

classmethod full() → JamConfig

Create full chain configuration.

classmethod from_chain(chain: str) → JamConfig

Create configuration from chain name.

__init__(chain: ChainSpec, num_validators: int, num_cores: int, slot_duration: int, epoch_duration: int, ticket_submission_end: int, contest_duration: int, tickets_per_validator: int, max_tickets_per_extrinsic: int, rotation_period: int | None) → None