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Indexer client

The indexer client is a standalone Go process that runs as a sidecar alongside an Ethereum validator node. It connects to the validator's Geth node, fetches every new block (with transactions, receipts, and logs), structures them into DefraDB documents, signs the batch, and publishes everything over P2P.

Indexers are write-only data producers. They push data out and reject all incoming replication.

Architecture

The indexer connects to Geth over two channels:

• WebSocket (port 8546): subscribes to new block headers for real-time feed.
• HTTP JSON-RPC (port 8545): fetches full block details, fills gaps on restart, handles historical ranges. This is a backup connection.

Data processing pipeline

Each block goes through six stages:

1. Receive: a new block header arrives over the WebSocket subscription.
2. Fetch: the full block is pulled over JSON-RPC, including the header, transactions, receipts, logs, and access lists.
3. Structure: raw data is transformed into the six document types.
4. Sign: a Merkle root is computed over all document CIDs and signed with the indexer's identity key.
5. Store: documents are written to the local embedded DefraDB.
6. Publish: DefraDB's P2P layer broadcasts to subscribed peers (hosts).

Document types

The indexer produces six document types per block. The first four come directly from on-chain data. The last two are metadata that the indexer itself produces.

Collection names use a chain prefix: Ethereum__Mainnet__Block, Optimism__Mainnet__Block, etc. Schema definitions live in pkg/schema/schema_standard.graphql. There are two schema variants:

• Standard: parallel transaction processing (default build).

Block

type Ethereum__Mainnet__Block {
    hash: String 
    number: Int 
    timestamp: String
    parentHash: String
    difficulty: String
    totalDifficulty: String
    gasUsed: String
    gasLimit: String
    baseFeePerGas: String
    nonce: String
    miner: String
    size: String
    stateRoot: String
    sha3Uncles: String
    transactionsRoot: String
    receiptsRoot: String
    logsBloom: String
    extraData: String
    mixHash: String
    uncles: [String]
    transactions: [Ethereum__Mainnet__Transaction] @relation(name: "block_transactions")
}

Transaction

Merges fields from both the transaction object and its receipt. Receipt-specific fields: status, gasUsed, cumulativeGasUsed, effectiveGasPrice.

type Ethereum__Mainnet__Transaction {
    hash: String
    blockHash: String 
    blockNumber: Int 
    from: String
    to: String
    value: String
    gas: String
    gasPrice: String
    gasUsed: String
    maxFeePerGas: String
    maxPriorityFeePerGas: String
    input: String
    nonce: String
    transactionIndex: Int
    type: String
    chainId: String
    v: String
    r: String
    s: String
    status: Boolean
    cumulativeGasUsed: String
    effectiveGasPrice: String
    block: Ethereum__Mainnet__Block @relation(name: "block_transactions")
    logs: [Ethereum__Mainnet__Log] @relation(name: "transaction_logs")
    accessList: [Ethereum__Mainnet__AccessListEntry] @relation(name: "transaction_accessList")
}

Log

Event logs emitted during transaction execution. topics is an array of hex-encoded indexed parameters (topic[0] is the event signature hash). data is the hex-encoded non-indexed parameters. No ABI decoding happens at this layer; everything is stored as raw hex.

AccessListEntry

EIP-2930 access list entries. Most transactions do not have access lists, so this collection is typically sparse.

type Ethereum__Mainnet__AccessListEntry {
    address: String
    storageKeys: [String]
    blockNumber: Int
    transaction: Ethereum__Mainnet__Transaction @relation(name: "transaction_accessList")
}

BlockSignature

Created after all documents for a block are written. Contains a Merkle root computed over all document CIDs for that block, signed with the indexer's identity key.

type Ethereum__Mainnet__BlockSignature {
    blockNumber: Int
    blockHash: String
    merkleRoot: String
    cidCount: Int
    cids: [String]
    signatureType: String
    signatureIdentity: String
    signatureValue: String
    createdAt: String
}

SnapshotSignature

Seals a range of blocks into a single signed snapshot. The merkleRoot is computed over the per-block BlockSignature Merkle roots within the range, not over individual document CIDs.

type Ethereum__Mainnet__SnapshotSignature {
    startBlock: Int
    endBlock: Int
    merkleRoot: String
    blockCount: Int
    signatureType: String
    signatureIdentity: String
    signatureValue: String
    createdAt: String
    snapshotFile: String
    blockSigMerkleRoots: [String]
}

Document signing

Signing is opt-in and configured by the indexer operator. Hosts disable it with --no-signing.

The signing flow:

1. At startup, the indexer loads a persistent identity from the DefraDB keyring using GetIdentityContext().
2. The identity is injected into the Go context via node.ContextWithBlockSigning(ctx, collector), which enables CID collection.
3. As the block handler writes documents, DefraDB collects the CID of each document written.
4. After all documents for a block are written, the indexer calls node.SignBlock, which computes a Merkle root over the collected CIDs, signs it, and writes the BlockSignature document.
5. Each individual document also gets a _version entry with identity and signature:

{
    "_version": [
        {
            "cid": "bafyreig5...",
            "height": 1,
            "signature": {
                "identity": "did:key:z6Mk...",
                "value": "0x3045022100..."
            }
        }
    ]
}

Pruning

The pruner removes old data to keep storage bounded. It uses a queue-based system and persists its state to {storePath}/prune_queue.gob.

Two queue implementations exist:

• IndexerQueue: tracks document IDs at creation time. When it prunes, it removes entire blocks at once (Block + all its Transactions, Logs, AccessListEntries, and BlockSignature).
• EventQueue: FIFO queue for P2P replication events. Drains documents as they arrive. Used by hosts, not indexers.

If the queue is empty (first run or after restart with no persisted state), the pruner falls back to filter-based pruning, querying DefraDB directly for old documents.

Note: BlockSignature is referenced as BatchSignature in parts of the app-sdk code. This is a naming inconsistency, not a separate type.

Snapshots

Snapshots bundle multiple blocks into a single signed file for faster initial sync.

Environment variables: SNAPSHOT_ENABLED, SNAPSHOT_BLOCKS_PER_FILE, SNAPSHOT_INTERVAL_SECONDS.

P2P data distribution

The indexer does not manage P2P connections directly. DefraDB handles all of that through libp2p:

1. The indexer writes a document.
2. DefraDB computes a content digest.
3. DefraDB gossips the digest to connected peers.
4. A peer that wants the document requests its full content.
5. DefraDB sends the full document.

This is unidirectional. The replication filter in pkg/indexer/replication_filter.go rejects all inbound documents. Indexers only push.

Bootstrap peers are configured in the DefraDB config. Peers are also discovered through EntityRegistered events from ShinzoHub.

Resource requirements

Configuration

GETH_RPC_URL=https://json-rpc.example.com
GETH_WS_URL=ws://ws.example.com
GETH_API_KEY=your_api_key
INDEXER_START_HEIGHT=0
SNAPSHOT_ENABLED=false
SNAPSHOT_BLOCKS_PER_FILE=1000
SNAPSHOT_INTERVAL_SECONDS=60
LOG_LEVEL=error

INDEXER_START_HEIGHT is the block number to start indexing from on first run with no existing data. Setting the value to 0 will start indexing at the tip of any chain. For a specific block select please use that blocknumber.

Chain abstraction (in progress)

The codebase is being refactored from EVM-only to support multiple chains. The approach splits the current monolithic logic into a Chain interface with three parts:

• Fetcher: retrieves raw block data from the chain-specific RPC.
• Converter: transforms chain-specific data into Shinzo's canonical document types.
• BlockHandler: writes documents to DefraDB (chain-agnostic).

Key files