Decimal Smart Chain Guard is a tool helping to monitor validator node and set it offline if node stops to sign blocks by any reason.

1. Start

2. Connect to multiple nodes: start partial watcher for every node

• watchers can infinity reconnect

3. Watch for blocks, validator set changes and count missed blocks

• periodicaly validate set_offline transaction. If transaction is valid (right account number, account sequence, chain id...) guard will report Check set_offline transaction ok otherwise it will report error

4. If validator is online and missed some count of blocks, then sends set_offline

5. Start watch without tx data

• if validator become online, report error about unprotected validator

6. Go to state 2-3 after get new set_offline tx data

To configure guard tool you should create file .env at directory cmd/dsc-guard. Example of the configuration:

NODES_ENDPOINTS=http://localhost:26657
MISSED_BLOCKS_LIMIT=8
MISSED_BLOCKS_WINDOW=24
NEW_BLOCK_TIMEOUT=10
FALLBACK_PAUSE=2
VALIDATOR_ADDRESS=1A42FDF9FC98931A4BB59EF571D61BB70417657D
HTTP_LISTENER=localhost:11111
SET_OFFLINE_TX=ab01282816a90a1a51f5833b0a14d0c71c31a891e5023ae63fd2bcf2732f04f32158120310be031a6a0a26eb5ae987210279f7e074d08a23e2fc7b7fd9e49a0d6570a28bf6c9cb988e92f678c32935097412407979e0cc483f241e48ed3c371d9d668a5b978fb474afc5fea5803c89bd2a2dac3db15eb84fef1fce25e783e279a33bac7b96bbe6786c9608d52c69baecacf9d02218446563696d616c2047756172642074726967676572726564

Where:

• NODES_ENDPOINTS - list of Decimal Node RPC endpoints which should be used to listen new blocks (can be specified several endpoints separated by ,, protocol scheme must be http/https)
• MISSED_BLOCKS_LIMIT and MISSED_BLOCKS_WINDOW - when at least MISSED_BLOCKS_LIMIT blocks of last MISSED_BLOCKS_WINDOW blocks are missed to sign by monitoring validator set_offline transaction will be send to all connected nodes to turn of validator
• NEW_BLOCK_TIMEOUT - timeout of receiving new block in seconds (if no new blocks are received during this duration then assumed node is disconnected)
• FALLBACK_PAUSE - time in seconds for reconnect to node
• VALIDATOR_ADDRESS - validator address in hex format which should be monitored by the guard. Validator address can be found in file $HOME/.decimal/daemon/config/priv_validator_key.json
• HTTP_LISTENER - address and port to provide http page with JSON report (see below); if you don't need this feature, set it to empty
• SET_OFFLINE_TX - signed tx (ready to broadcast) in hex format which will be used to turn off validator when too many blocks are missed to sign

Current status of guard for monitoring For example if HTTP_LISTENER=localhost:11111, then http://127.0.0.1:11111/ will return page with following JSON:

{
    "critical":"",
    "current_height":45080,
    "transaction_status":"valid",
    "validator_online":true,
    "watchers_count":3,
    "watchers_watching":3
}

• critical: empty string. It will be filled when:
  • all watchers of guard can't connect to nodes
  • validator is online and transaction is invalid
  • no new block after NEW_BLOCK_TIMEOUT seconds: blockchain is stuck or all listening nodes disconnected from blockchain
• current_height - current blockchain height (block)
• transaction_status - valid, invalid, unknown (when guard starts)
• validator_online - boolena, true when validator online
• watchers_count - count of watchers/nodes to listen
• watchers_watching - count of watchers, connected to nodes, and watching (listening) node