tendermint/docs/architecture/adr-052-tendermint-mode.md

ADR 052: Tendermint Mode

Changelog

• 27-11-2019: Initial draft from ADR-051
• 13-01-2020: Separate ADR Tendermint Mode from ADR-051
• 29-03-2021: Update info regarding defaults

Context

• Full mode: full mode does not have the capability to become a validator.
• Validator mode : this mode is exactly same as existing state machine behavior. sync without voting on consensus, and participate consensus when fully synced
• Seed mode : lightweight seed node maintaining an address book, p2p like TenderSeed

Decision

We would like to suggest a simple Tendermint mode abstraction. These modes will live under one binary, and when initializing a node the user will be able to specify which node they would like to create.

• Which reactor, component to include for each node
  • full
    • switch, transport
    • reactors
      • mempool
      • consensus
      • evidence
      • blockchain
      • p2p/pex
      • statesync
    • rpc (safe connections only)
    • no privValidator(priv_validator_key.json, priv_validator_state.json)
  • validator
    • switch, transport
    • reactors
      • mempool
      • consensus
      • evidence
      • blockchain
      • p2p/pex
      • statesync
    • rpc (safe connections only)
    • with privValidator(priv_validator_key.json, priv_validator_state.json)
  • seed
    • switch, transport
    • reactor
      • p2p/pex
• Configuration, cli command
  • We would like to suggest by introducing mode parameter in config.toml and cli
  • mode = "{{ .BaseConfig.Mode }}" in config.toml
  • tendermint start --mode validator in cli
  • full | validator | seednode
  • There will be no default. Users will need to specify when they run tendermint init
• RPC modification
  • host:26657/status
    • return empty validator_info when in full mode
  • no rpc server in seednode
• Where to modify in codebase
  • Add switch for config.Mode on node/node.go:DefaultNewNode
  • If config.Mode==validator, call default NewNode (current logic)
  • If config.Mode==full, call NewNode with nil privValidator (do not load or generation)
    • Need to add exception routine for nil privValidator to related functions
  • If config.Mode==seed, call NewSeedNode (seed node version of node/node.go:NewNode)
    • Need to add exception routine for nil reactor, component to related functions

Status

Implemented

Consequences

Positive

• Node operators can choose mode when they run state machine according to the purpose of the node.
• Mode can prevent mistakes because users have to specify which mode they want to run via flag. (eg. If a user want to run a validator node, she/he should explicitly write down validator as mode)
• Different mode needs different reactors, resulting in efficient resource usage.

Negative

• Users need to study how each mode operate and which capability it has.

Neutral

References

• Issue #2237 : Tendermint "mode"
• TenderSeed : A lightweight Tendermint Seed Node.