Setup Watchers (Blockchain Indexers)

Overview

Watchers are services that index blockchain data (blocks, transactions, events) and feed deposits and other on-chain events into the platform (DB, ledger, notifications).

What watchers do

  1. Connect to chain RPC (TON, TRON, etc.).
  2. Track last processed block/cursor (stored in DB or file).
  3. Poll or subscribe for new blocks/transactions.
  4. Parse transfers and contract events (e.g. TRC20).
  5. Persist deposits and emit events (e.g. NATS) for downstream (wallet, bot, ledger).

High-level flow

flowchart LR
  A[Chain RPC] --> B[Watcher]
  B --> C[Cursor Store]
  B --> D[Deposit / Event]
  D --> E[DB + Outbox]
  E --> F[NATS / Bot]

Setup steps

1. Cursor and idempotency

  • Store chain_id + last_block (or last_tx_hash) in a table (e.g. chain_cursors).
  • On restart, resume from last persisted cursor; never process the same block twice (idempotent inserts by tx_hash or equivalent).

2. Configuration

  • RPC URL, poll interval, confirmation depth (e.g. 12 blocks).
  • Use env or config file; no secrets in code.

3. Deposit pipeline

  • Parse tx → user (e.g. by deposit address from Wallet), amount, asset, tx_hash.
  • Insert into deposits (or equivalent) with idempotency key.
  • Write to outbox for notifications (e.g. “Deposit confirmed”) and ledger credits.

4. Reorg handling

  • For PoW/PoS chains, use confirmation depth; for TON/TRON, follow chain best practices (e.g. finality rules).

Where watchers live

  • TON/TRON watchers may live in the Watcher service or in chain-specific packages under packages/blockchain/.
  • Gateway does not run watchers; they run as separate processes or containers.

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