midnight-node-node-validator

name: midnight-node:node-validator description: This skill should be used when the user asks about running a Midnight validator end-to-end — generating validator session keys, becoming a permissioned (federated) or registered (staked) candidate, how the committee is selected via the D-parameter and Ariadne, committee rotation per Cardano epoch, producing blocks with --validator, and testing a validator locally with the mock main-chain follower. Covers "how do I run a validator", "become a block producer", "permissioned vs registered candidate", "validator committee selection", "validator not producing blocks", and "register as a Midnight validator". version: 0.1.0

Running a Midnight Validator

End-to-end operator journey: provision keys → join a candidate pool → get selected into the committee by Ariadne → produce blocks.

This skill owns the candidate model and committee-selection narrative. Operational flags live in midnight-node:node-operations; key provisioning details are in midnight-node:node-configuration → references/validator-keys.md; the full committee-selection deep-dive is in references/committee-and-candidates.md (this skill's own reference file). For the local Docker stack see midnight-tooling:devnet.

Journey Overview

1. Provision keys
   AURA_SEED_FILE  (Sr25519 / aura)
   GRANDPA_SEED_FILE (Ed25519 / gran)
   CROSS_CHAIN_SEED_FILE (ECDSA / crch)
          │
          ▼
2. Join a candidate pool
   ┌──────────────────┬──────────────────────────────┐
   │ Permissioned     │ Registered                   │
   │ (federated)      │ (staked)                     │
   │ declared in      │ posted as Cardano UTXO;      │
   │ chain config     │ read via main-chain follower  │
   └──────────────────┴──────────────────────────────┘
          │
          ▼
3. Ariadne selection (once per Cardano epoch)
   D-parameter (num_permissioned, num_registered)
   from pallet_system_parameters
          │
          ▼
4. Committee stored in pallet_session_validator_management
   current_committee_storage() / next_committee_storage()
          │
          ▼
5. Block production
   midnight-node --validator
   (AURA assigns slots to committee members)

Step 1 — Validator Keys

Midnight validators require exactly three session keys. BEEFY is NOT a fourth key — it is commented out with a TODO in SessionKeys (runtime/src/lib.rs:221-228) and is not provisioned at node-1.0.0.

Sources: runtime/src/lib.rs:162,183; partner-chains/toolkit/partner-chains-cli/src/keystore.rs:19-26.

# Generate seed files (one per key type in production)
midnight-node key generate --scheme sr25519   # AURA
midnight-node key generate --scheme ed25519   # GRANDPA
midnight-node key generate --scheme ecdsa     # CROSS_CHAIN

# Dev shortcut — all three from the same dev path
echo "//Alice" > /tmp/alice-seed
AURA_SEED_FILE=/tmp/alice-seed \
GRANDPA_SEED_FILE=/tmp/alice-seed \
CROSS_CHAIN_SEED_FILE=/tmp/alice-seed \
CFG_PRESET=dev midnight-node --validator

For full key-generation options, author_insertKey / author_rotateKeys RPC calls, and production security guidance, see midnight-node:node-configuration → references/validator-keys.md.

Step 2 — Become a Candidate

There are two distinct candidate pools. A node must appear in at least one pool to be eligible for committee selection.

Key point: candidate registration for the staked pool is a Cardano-side / partner-chains framework action, not a Midnight node extrinsic. The midnight-node binary contains no register_candidate extrinsic — it only reads registrations from the Cardano chain via the main-chain follower.

For the full candidate-pool mechanics, weight calculation, and Ariadne inputs, see references/committee-and-candidates.md.

Step 3 — Committee Selection

Once per Cardano epoch the runtime selects the next committee using Ariadne.

D-parameter (num_permissioned, num_registered) controls how many seats each pool gets. It is authoritative in pallet_system_parameters storage (pallets/system-parameters/src/lib.rs:86).

// runtime/src/lib.rs:541-549
fn select_authorities_optionally_overriding(
    mut input: AuthoritySelectionInputs,
    sidechain_epoch: ScEpochNumber,
) -> Option<BoundedVec<CommitteeMember<CrossChainPublic, SessionKeys>, MaxAuthorities>> {
    let d_parameter = SystemParameters::get_d_parameter();
    input.d_parameter.num_permissioned_candidates = d_parameter.num_permissioned_candidates;
    input.d_parameter.num_registered_candidates   = d_parameter.num_registered_candidates;
    select_authorities(Sidechain::genesis_utxo(), input, sidechain_epoch)
}

The function overrides the D-parameter in the inherent data with the live on-chain value, then forwards to select_authorities from the partner-chains framework. Ariadne v2 blends the two pools with weighted proportional selection, backfilling empty pools.

To update the D-parameter via on-chain governance, see midnight-node:node-governance.

Step 4 — Committee Rotation

pallet_session_validator_management (aliased SessionCommitteeManagement at runtime/src/lib.rs:934) stores the active and pending committees.

Rotation timing: ValidatorManagementSessionManager promotes next_committee → current_committee at each Cardano epoch boundary and increments pallet_session::pallet::CurrentIndex. A committee computed for epoch N takes effect at epoch N+1 for AURA/GRANDPA authority lists.

For the full rotation flow and SessionValidatorManagementApi runtime API, see references/committee-and-candidates.md.

Step 5 — Produce Blocks

Start the node with --validator to activate block production. The AURA consensus assigns each slot to a committee member by rotating through the AURA public keys in the current committee list.

CFG_PRESET=preview midnight-node \
  --validator \
  --name "my-validator"

The node must have:

• All three seed files resolved (AURA, GRANDPA, CROSS_CHAIN)
• Membership in the current committee (check via current_committee_storage())
• Sufficient peers and stable uptime

For --validator flag details, monitoring, and diagnostic RPC calls, see midnight-node:node-operations. For AURA slot assignment and GRANDPA finality internals, see midnight-node:node-architecture → references/consensus-and-finality.md.

Local Validator Testing (Mock Main-Chain Follower)

To run a full validator committee locally without a Cardano node or db-sync instance, enable the mock main-chain follower in midnight.toml:

use_main_chain_follower_mock = true
mock_registrations_file = "/path/to/mock-registrations.json"

Source: node/src/cfg/midnight_cfg/mod.rs:45-49; validation at lines 116-119.

mock_registrations_file is a JSON file that substitutes for Cardano registration UTXOs. It supplies the AuthoritySelectionDataSourceMock used by the inherent provider.

For the full mock data-source mechanics, see references/committee-and-candidates.md → Data Sources section. For local stack management, see midnight-tooling:devnet.

Troubleshooting

References

Cross-References