Release Stuck EVM Transactions

You can programatically cancel or accelerate a "stuck" EVM transaction.

Background: EVM nonce handling

Every transaction over the Ethereum and account-based networks has a specific nonce. The first transaction sent from a particular address and vault has nonce 0, the second nonce 1, and so forth. For a given address and chain, each outgoing transaction’s nonce is unique, and must be exactly one more than the previous one (no gaps are allowed).

Fordefi increments the nonce whenever a transaction is pushed to the blockchain so that the transaction that will be signed next will have the following nonce. This prevents nonce collisions and takes the burden of handling the nonce from the users.

Stuck transactions

If a previously submitted transaction was submitted with low fees, it may be stuck in the mempool. Moreover, due to the sequential nature of nonces in EVM chains, any subsequent transactions from the same vault on the same chain will be "queued" in the mempool—each transaction waiting for all the transactions with smaller nonces to complete.

Release a stuck transaction

Fordefi lets you cancel or accelerate stuck transactions. This is achieved by sending a new transaction on chain with the same nonce as the stuck transaction and a fee that should be adjusted to the current network congestion, but no less than 12% above the original transaction.

• Accelerate creates exactly the same transaction as the original, only with higher fees.
• Cancel sends 0 ETH (or the base asset on any other chain) to yourself, with a higher fee.

Learn more about canceling and accelerating transactions using the Fordefi web console.

To programmatically release a transaction, you need to call the Release Transaction API by sending a POST request to the /api/v1/transactions/{id}/release endpoint, where {id} is the ID of the original transaction.

You need to authenticate your request, similarly to how you authenticate Create Transaction requests. Specifically:

• Pass the Access Token in the Authorization: Bearer <TOKEN> header.
• Sign the request body with the API User’s private key, the public key of which you have registered with the API Signer. Use the ECDSA signature scheme over the NIST P-256 curve. The signed message is comprised of the API endpoint timestamp, and request body. Pass the signature in a x-signature HTTP header of your POST request.

You can use the following code samples:

#!bash
ACCESS_TOKEN='<API User access token>'
PRIVATE_KEY_FILE='private.pem'
TXN_ID='<Transction ID>'
RELEASE_TYPE="cancel" # can be "cancel" or "accelerate"

ENDPOINT="/api/v1/transactions/${TXN_ID}/release"
TIMESTAMP="$(($(date +%s) * 1000))"

BODY='{
    "type": "evm_transaction",
    "release_type": "'${RELEASE_TYPE}'",
    "signer_type": "api_signer"
}'

print ${BODY}

SIGNATURE="$(echo -n "${ENDPOINT}|${TIMESTAMP}|${BODY}" | openssl dgst -sha256 -sign ${PRIVATE_KEY_FILE} | base64 | tr -d \\n)"

echo -n "${ENDPOINT}|${TIMESTAMP}|${BODY}"

curl "https://api.fordefi.com${ENDPOINT}" \
-H "Authorization: Bearer ${ACCESS_TOKEN}" \
-H "Content-Type: application/json" \
-H "x-signature: ${SIGNATURE}" \
-H "x-timestamp: ${TIMESTAMP}" \
-d "${BODY}"

Transaction information

Once cancelled or accelerated, the original transaction includes a child_transaction_id field, which contains the id of the newly created replacement transaction. The replacement transactions points back to the original transaction in its parent_transaction_id field and also has its is_cancelation or is_acceleration fields set. You can obtain the transaction objects that contain these data using the Get Transaction endpoint.