Gasolina API Reference

This page documents the Gasolina REST API endpoints, request/response formats, and integration patterns. The Gasolina API is a lightweight service that verifies LayerZero messages and produces signatures for DVN contracts.

Base URL

After deploying Gasolina, your API will be available at:

AWS: https://<api-gateway-id>.execute-api.<region>.amazonaws.com
GCP: https://<service-name>-<hash>.a.run.app

Endpoints

Health Check

Verify that the Gasolina service is running.

GET /

Response:

HEALTHY

Example:

curl https://your-gasolina-instance.com/

Get Signer Info

Retrieve the signer addresses registered with this Gasolina instance for a specific chain.

GET /signer-info?chainName={chainName}

Query Parameters:

Parameter	Type	Required	Description
`chainName`	string	Yes	The chain name (e.g., `ethereum`, `bsc`, `arbitrum`)

Response:

{
  signers: string[]  // Array of signer addresses
}

Example:

curl "https://your-gasolina-instance.com/signer-info?chainName=ethereum"

Response:

{
  "signers": [
    "0x1234567890123456789012345678901234567890",
    "0x0987654321098765432109876543210987654321"
  ]
}

The signer addresses returned here are what LayerZero uses when deploying the DVN contracts. These addresses must match the signers registered in the onchain DVN contract.

Request Signatures

Request signatures for a LayerZero message verification. This is the primary endpoint called by Essence to obtain verification signatures.

POST /

Request Body:

interface SignatureRequest {
  lzMessageId: {
    srcUAAddress: string; // Source OApp address
    dstUAAddress: string; // Destination OApp address
    srcChainId: string; // Source endpoint ID
    dstChainId: string; // Destination endpoint ID
    srcChainName: string; // Source chain name (e.g., "ethereum")
    dstChainName: string; // Destination chain name (e.g., "bsc")
    nonce: number; // Message nonce
  };
  srcTxHash: string; // Source transaction hash
  expiration: number; // Signature expiration (Unix timestamp)
  blockConfirmation: number; // Required block confirmations
  ulnVersion: 'V2' | 'V302'; // ULN version
  self?: string; // Optional: self reference for callbacks
  skipVId?: boolean; // Optional: skip VID validation
}

Response:

interface SignatureResponse {
  body: {
    signatures: Array<{
      signature: string; // Hex-encoded ECDSA signature
      address: string; // Signer address (for verification)
    }>;
  };
}

Example Request:

curl -X POST https://your-gasolina-instance.com/ \
  -H "Content-Type: application/json" \
  -d '{
    "lzMessageId": {
      "srcUAAddress": "0x4fa745fccc04555f2afa8874cd23961636cdf982",
      "dstUAAddress": "0xe9f183fc656656f1f17af1f2b0df79b8ff9ad8ed",
      "srcChainId": "101",
      "dstChainId": "102",
      "srcChainName": "ethereum",
      "dstChainName": "bsc",
      "nonce": 190
    },
    "srcTxHash": "0x2c58710ed1a83e2fff10adb0eb2b70f9262df6937d45e65a6fca5f2a043e7332",
    "expiration": 1701410857,
    "blockConfirmation": 15,
    "ulnVersion": "V2",
    "skipVId": false
  }'

Example Response:

{
  "body": {
    "signatures": [
      {
        "signature": "0x1234...abcd",
        "address": "0x1234567890123456789012345678901234567890"
      },
      {
        "signature": "0x5678...efgh",
        "address": "0x0987654321098765432109876543210987654321"
      }
    ]
  }
}

Request Parameters Reference

lzMessageId Object

Field	Type	Description
`srcUAAddress`	string	The OApp address on the source chain
`dstUAAddress`	string	The OApp address on the destination chain
`srcChainId`	string	LayerZero endpoint ID of the source chain
`dstChainId`	string	LayerZero endpoint ID of the destination chain
`srcChainName`	string	Human-readable source chain name
`dstChainName`	string	Human-readable destination chain name
`nonce`	number	Sequential message nonce for this pathway

Top-Level Fields

Field	Type	Description
`srcTxHash`	string	Transaction hash where `PacketSent` was emitted
`expiration`	number	Unix timestamp after which signature is invalid
`blockConfirmation`	number	Number of block confirmations required
`ulnVersion`	string	`"V2"` for ULNv2, `"V302"` for ULN302
`self`	string?	Optional callback reference
`skipVId`	boolean?	If true, skip VID validation (default: false)

ULN Version Selection

Version	Description	When to Use
`V2`	Legacy ULN version	For messages using ULNv2 Message Library
`V302`	Current ULN version	For messages using ULN302 Message Library

Error Responses

HTTP Status Codes

Status	Meaning	Common Causes
`200`	Success	Signatures generated successfully
`400`	Bad Request	Invalid request body or parameters
`404`	Not Found	Chain not supported or message not found
`500`	Internal Error	RPC failure or signing error

Common Error Scenarios

Chain Not Supported

{
  "error": "Chain not available",
  "chainName": "unsupported-chain"
}

Solution: Ensure the chain is listed in your availableChainNames configuration and has RPC providers configured.

Message Not Found

{
  "error": "PacketSent event not found",
  "txHash": "0x..."
}

Solution: Verify the transaction hash is correct and the transaction has been mined. Check that your RPC providers are synced.

Block Confirmations Not Met

{
  "error": "Insufficient block confirmations",
  "required": 15,
  "current": 5
}

Solution: Wait for more blocks to be mined before retrying the request.

RPC Provider Error

{
  "error": "Failed to connect to RPC provider"
}

Solution: Check RPC provider configuration and ensure endpoints are accessible. Consider adding backup providers.

Testing Your API

Using the Test Script

Both gasolina-aws and gasolina-gcp include a test script:

# From repository root
ts-node scripts/testDeployment.ts -u <your-api-url> -e <environment>

Options:

Flag	Description
`-u, --url`	Your Gasolina API URL
`-e, --environment`	`mainnet` or `testnet`

Successful Response:

--- Sending request to https://your-api.com ---
Sample request: { lzMessageId: {...}, srcTxHash: '0x...', ... }
--- [200] Successful request ---
Response: {
  signatures: [
    { signature: '<signature>', address: '<address>' },
    { signature: '<signature>', address: '<address>' }
  ]
}

Manual Testing

Test health check:

curl https://your-gasolina-instance.com/
# Expected: HEALTHY

Test signer info:

curl "https://your-gasolina-instance.com/signer-info?chainName=ethereum"
# Expected: { "signers": ["0x...", "0x..."] }

Test with sample message:

# Create a test payload file
cat > test-payload.json << 'EOF'
{
  "lzMessageId": {
    "srcUAAddress": "0xc769361cce2a4a61572d59faf3b58065c6faac04",
    "dstUAAddress": "0xc769361cce2a4a61572d59faf3b58065c6faac04",
    "srcChainId": "40161",
    "dstChainId": "40102",
    "srcChainName": "sepolia",
    "dstChainName": "bsc",
    "nonce": 1
  },
  "srcTxHash": "0xc5171abb2c8601ff5062c27c12f32c609b89eb38876a2509a4cd6d5327c64564",
  "expiration": 1701493303,
  "blockConfirmation": 1,
  "ulnVersion": "V302",
  "skipVId": true
}
EOF

# Send test request
curl -X POST https://your-gasolina-instance.com/ \
  -H "Content-Type: application/json" \
  -d @test-payload.json

Extra Context Verification API

If you’ve configured extra context verification, Gasolina will call your custom API for additional validation.

Request Format (to your API)

interface ExtraContextRequest {
  sentEvent: {
    lzMessageId: {
      pathwayId: {
        srcEid: number;
        dstEid: number;
        sender: string;
        receiver: string;
        srcChainName: string;
        dstChainName: string;
      };
      nonce: number;
      ulnSendVersion: string;
    };
    guid: string;
    message: string;
    options: {
      lzReceive?: {gas: string; value: string};
      nativeDrop?: Array<{amount: string; receiver: string}>;
      compose?: Array<{index: number; gas: string; value: string}>;
      ordered?: boolean;
    };
    payload?: string;
    sendLibrary?: string;
    onChainEvent: {
      chainName: string;
      txHash: string;
      blockHash: string;
      blockNumber: number;
    };
  };
  from: string;
}

Expected Response

Your API should return a boolean indicating whether the message should be signed:

{
  "valid": true
}

Or to reject:

{
  "valid": false
}

Rate Limiting Considerations

While Gasolina doesn’t implement rate limiting by default, consider these factors:

RPC Provider Limits: Your RPC providers may have rate limits that affect signature generation speed.
Cloud Provider Limits:
- AWS API Gateway has default throttling limits
- GCP Cloud Run has concurrency limits
Scaling:
- AWS ECS auto-scales based on CPU/memory
- GCP Cloud Run auto-scales based on request volume

Security Considerations

No Authentication by Default: The API is publicly accessible. Consider adding:
- IP allowlisting at the load balancer level
- API key authentication if needed
- VPC/private endpoints for internal access
Signer Key Security:
- Keys are never exposed via the API
- Only signatures are returned, not private key material
Request Validation:
- Gasolina independently verifies events via RPC
- Block confirmation requirements are enforced
- Invalid requests are rejected before signing

Gasolina Overview - Architecture and security model
Implementation Guide - Deployment instructions
DVN Troubleshooting - Debugging common issues
DVN Technical Reference - Contract methods and events

Workers

DVN Overview

Gasolina DVN

Build Custom DVNs & Executors

Reference

Gasolina API Reference

Base URL

Endpoints

Health Check

Get Signer Info

Request Signatures

Request Parameters Reference

lzMessageId Object

Top-Level Fields

ULN Version Selection

Error Responses

HTTP Status Codes

Common Error Scenarios

Chain Not Supported

Message Not Found

Block Confirmations Not Met

RPC Provider Error

Testing Your API

Using the Test Script

Manual Testing

Extra Context Verification API

Request Format (to your API)

Expected Response

Rate Limiting Considerations

Security Considerations

Workers

DVN Overview

Gasolina DVN

Build Custom DVNs & Executors

Reference

​Base URL

​Endpoints

​Health Check

​Get Signer Info

​Request Signatures

​Request Parameters Reference

​lzMessageId Object

​Top-Level Fields

​ULN Version Selection

​Error Responses

​HTTP Status Codes

​Common Error Scenarios

​Chain Not Supported

​Message Not Found

​Block Confirmations Not Met

​RPC Provider Error

​Testing Your API

​Using the Test Script

​Manual Testing

​Extra Context Verification API

​Request Format (to your API)

​Expected Response

​Rate Limiting Considerations

​Security Considerations

​Related Resources

Base URL

Endpoints

Health Check

Get Signer Info

Request Signatures

Request Parameters Reference

lzMessageId Object

Top-Level Fields

ULN Version Selection

Error Responses

HTTP Status Codes

Common Error Scenarios

Chain Not Supported

Message Not Found

Block Confirmations Not Met

RPC Provider Error

Testing Your API

Using the Test Script

Manual Testing

Extra Context Verification API

Request Format (to your API)

Expected Response

Rate Limiting Considerations

Security Considerations

Related Resources