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chaind-eth development tester recipe

chaind-eth is a socket server that acts as a automated transaction handler for an EVM network.

It capabilities are (unchecked box means feature not yet completed):

  • unix socket server to accept raw, signed RLP evm transactions
  • stateful queueing system following full local and remote lifecycle of the transaction
  • transaction dispatcher unit
  • transaction retry unit (for errored or suspended transactions)
  • blockchain listener that updates state of transactions in queue
  • CLI transaction listing tool, filterable by:
    • transaction range with lower and/or upper bound
    • only show transaction with errors
    • only show transaction that have not yet completed
  • systemd unit / socket service
  • sql storage backend
  • filesystem storage backend


For these examples you need:

  • linux (tested on 5.12.x, perhaps wsl/macos will work too, no guarantees, though)
  • python 3.9.x
  • pip
  • virtualenv
  • socat
  • sqlite
  • an EVM RPC endpoint

For any python command / executable used below:

  • add -v or -vv to get more information about what is going on
  • use with --help for information on how to use and parameters that can be passed

setting up the database backend

Currently there is no more practical way of setting up the database backend than to pull the repository and run a database migration script :/

git clone
cd chaind
python -m venv .venv
. .venv/bin/activate
pip install --extra-index-url -r requirements.txt
# the following will set up your database in ~/.local/share/chaind/eth/chaind.sqlite

usage example

create an empty working directory

In terminal window A

d=$(mktemp -d) && cd $d

create a chaind-eth sandbox

python -m venv .venv
. .venv/bin/activate
pip install --extra-index-url "chaind-eth>=0.0.3a5"

start the services

In terminal window B

cd <working directory>
. .venv/bin/activate
export DATABASE_ENGINE=sqlite
export RPC_PROVIDER=<your_provider>
export CHAIN_SPEC=<chain_spec_of_provider>
chaind-eth-server --session-id testsession

In terminal window C

cd <working directory>
. .venv/bin/activate
export DATABASE_ENGINE=sqlite
export RPC_PROVIDER=<your_provider>
export CHAIN_SPEC=<chain_spec_of_provider>

prepare test transactions

Create two transactions from sender in keyfile (which needs to have gas balance) to a newly created account

export WALLET_KEY_FILE=<path_to_keyfile>
export WALLET_PASSWORD=<keyfile_password_if_needed>
export RPC_PROVIDER=<your_provider>
export CHAIN_SPEC=<chain_spec_of_provider>

# create new account and store address in variable
eth-keyfile -z > testkey.json
recipient=$(eth-keyfile -z -d testkey.json)

# create transactions
eth-gas --raw -a $recipient 1024 > tx1.txt
eth-gas --raw -a $recipient 2048 > tx2.txt
eth-gas --raw -a $recipient 4096 > tx3.txt

send test transactions to queue

cat tx1.txt | socat UNIX-CLIENT:/run/user/$UID/chaind/eth/testsession/chaind.sock -
cat tx2.txt | socat UNIX-CLIENT:/run/user/$UID/chaind/eth/testsession/chaind.sock -
cat tx3.txt | socat UNIX-CLIENT:/run/user/$UID/chaind/eth/testsession/chaind.sock -

check status of transactions

chainqueue-list outputs details about transactions in the queue.

Provided the initial database migration was executed as described above, the execution would look as follows:

export DATABASE_ENGINE=sqlite
export DATABASE_NAME=$HOME/.local/share/chaind/eth/chaind.sqlite 
export CHAIN_SPEC=<chain_spec_of_provider>
sender=$(eth-keyfile -d $WALLET_KEY_FILE)
chainqueue-list $sender

To show a summary only instead all transactions:

chainqueue-list --summary $sender

The chaind-list tool can be used to list by session id. Following the above examples:

export DATABASE_ENGINE=sqlite
export CHAIN_SPEC=<chain_spec_of_provider>
chaind-list testsession

The chainqueue-list and chaind-list tools both provides the same basic filtering. Use --help to see the details.

Retrieve transaction by hash

The socket server returns the transaction hash when a transaction is submitted.

If a socket server is given a transaction hash, it will return the transaction data for that hash (if it exists).

Extending the previous examples, this will output the original signed transaction:

eth-gas --raw -a $recipient 1024 > tx1.txt
cat tx1.txt | socat UNIX-CLIENT:/run/user/$UID/chaind/eth/testsession/chaind.sock - | cut -b 4- > hash1.txt 
cat hash1.tx | socat UNIX-CLIENT:/run/user/$UID/chaind/eth/testsession/chaind.sock - | cut -b 4- > tx1_recovered.txt
diff tx1_recovered.txt tx1.txt
# should output 0
echo $?

The first 4 bytes of the data returned from the socket is a 32-bit big-endian result code. The data payload follows from the 5th byte.

Batch processing

The chaind-eth-send executable generates signed transactions with data from a csv file.

The data columns must be in the following order:

  1. receipient address
  2. transaction value
  3. token specifier (optional, network fee token if not given)
  4. network fee token value (optional)

If the gas token value (4) is not given for a gas token transaction, the transaction value (2) will be used.

By default the signed transactions are output as hex to stdout, each on a separate line.

If a valid --socket is given (i.e. the socket of the chaind-eth-server) the transactions will be send to the socket instead. The hash of the transaction will be output to standard output.

Using token symbols

If token symols are to be used in some or all values of column 3, then a valid --token-index executable address is required (in this case, a smart contract implementing the registry contract interface).

Input validity checks

The validity of the input data is verified before actual execution takes place.

These checks include:

  • The token can be made sense of.
  • The values can be parsed to integer amounts.
  • The recipient address is a valid checksum address.

The checks do however not include whether the token balances of the signer are sufficient to successfully execute the transactions on the network.

CSV input example


This will result in the following transactions:

  1. send 10 tokens from token contract 0xb708175e3f6Cd850643aAF7B32212AFad50e2549 to recipient 0x72B70906fD07c72f2d96aAA250C2D31662D0d809.
  2. send 42 GFT tokens along with 100 network gas tokens to recipient 0xD536CB6d1d9B8d33875E0ba0Aa3515eD7478f889
  3. send 666 network gas tokens to recipient 0xeE08b59a95E822AE346489038D25750C8EdfcC25

Resending transactions

Since the chaind-eth-server does not have access to signing keys, resending stalled transactions is also a separate external action.

The chaind-eth-resend executable takes a list of signed transactions (e.g. as output from chaind-eth-send using the socket) and automatically increases the fee price of the transaction to create a replacement.

As with chaind-eth-send, the resend executable optionally takes a socket argument that sends the transaction directly to a socket. Otherwise, the signed transactions are send to standard output.

For example, the following will output details of the transaction generated by chaind-eth-resend, in which the fee price has been slightly incremented:

eth-gas --raw --fee-price 100000000 -a $recipient 1024 > tx1.txt
chaind-eth-resend tx1.txt > tx1_bump.txt
cat tx1_bump.txt | eth-decode

Retrieving transactions for resend

The chaind-list tool can be used to retrieve transactions with the same filters as chainqueue-list, but also allowing results limited a specific session id.

As with chainqueue-list, which column to output can be customized. This enables creation of signed transaction lists in the format accepted by chaind-eth-resent.

One examples of criteria for transactions due to be resent may be:

# get any pending transaction in session "testsession"
export DATABASE_ENGINE=sqlite
chaind-list -o signedtx --pending testsession

Note that the chaind-list tool requires a connection to the queueing backend.