Multiple transactions from same address

Question

I would like to create multiple transaction from the same address at the same time. Since every transaction needs nonce (tx count of the sender address) I can ask geth for the current count and create first tx, then increment nonce and create the next one and so on. Problems as I see them are:

1. if one transaction does not get mined, none of the following will get mined (since nonce will be incorrect).
2. what happens if some tx gets included in one block and some in the other block, order might become wrong. Is this reasoning correct?

If it is not, I'm wondering is there any better approach for this case.

Answer 1

You have not stated whether you are sending your transactions while connected to the blockchain via geth (on-blockchain), or whether you are crafting your transaction while not connected to the blockchain (off-blockchain).

The answer by Paul S is referring to the off-blockchain crafting of transaction where you have to specify a nonce in the raw transactions you are then executing on the blockchain.

If you are sending your transaction on-blockchain, you can use the eth.sendTransaction(...) without a nonce.

For example, here are 3 transactions from the same "from" account to the same "to" account. There is no need to specify a nonce as it is automatically generated:

> eth.sendTransaction({from: '0x5e83b635f96da0752f991f0ebddc31249f452dea', to: '0x68acc3a13441b69016560d23e134c7931bbb27bb', value: web3.toWei(1, "ether")});
"0x92d6d2285b198b6b5cf80eca6d4292c9675fb53f47f786063df600d3be06dd09"
> eth.sendTransaction({from: '0x5e83b635f96da0752f991f0ebddc31249f452dea', to: '0x68acc3a13441b69016560d23e134c7931bbb27bb', value: web3.toWei(2, "ether")});
"0x0c1280c8b2f38aec032494913c1d0e65edd511fcd15e2424483f9bbf51c7172e"
> eth.sendTransaction({from: '0x5e83b635f96da0752f991f0ebddc31249f452dea', to: '0x68acc3a13441b69016560d23e134c7931bbb27bb', value: web3.toWei(3, "ether")});
"0x8b6998eea8b343a0f754cf2732a1f28caac3acdfbe97cca69f244f0614ea546a"

> eth.getTransaction("0x92d6d2285b198b6b5cf80eca6d4292c9675fb53f47f786063df600d3be06dd09");
{
  blockHash: "0x8456088424a4cacd8b394b4e11732e3c96ca77ab4a999c6ba62b38ab61116b58",
  blockNumber: 225,
  from: "0x5e83b635f96da0752f991f0ebddc31249f452dea",
  gas: 90000,
  gasPrice: 20000000000,
  hash: "0x92d6d2285b198b6b5cf80eca6d4292c9675fb53f47f786063df600d3be06dd09",
  input: "0x",
  nonce: 0,
  to: "0x68acc3a13441b69016560d23e134c7931bbb27bb",
  transactionIndex: 0,
  value: 1000000000000000000
}
> eth.getTransaction("0x0c1280c8b2f38aec032494913c1d0e65edd511fcd15e2424483f9bbf51c7172e");
{
  blockHash: "0x8456088424a4cacd8b394b4e11732e3c96ca77ab4a999c6ba62b38ab61116b58",
  blockNumber: 225,
  from: "0x5e83b635f96da0752f991f0ebddc31249f452dea",
  gas: 90000,
  gasPrice: 20000000000,
  hash: "0x0c1280c8b2f38aec032494913c1d0e65edd511fcd15e2424483f9bbf51c7172e",
  input: "0x",
  nonce: 1,
  to: "0x68acc3a13441b69016560d23e134c7931bbb27bb",
  transactionIndex: 1,
  value: 2000000000000000000
}
> eth.getTransaction("0x8b6998eea8b343a0f754cf2732a1f28caac3acdfbe97cca69f244f0614ea546a");
{
  blockHash: "0x8456088424a4cacd8b394b4e11732e3c96ca77ab4a999c6ba62b38ab61116b58",
  blockNumber: 225,
  from: "0x5e83b635f96da0752f991f0ebddc31249f452dea",
  gas: 90000,
  gasPrice: 20000000000,
  hash: "0x8b6998eea8b343a0f754cf2732a1f28caac3acdfbe97cca69f244f0614ea546a",
  input: "0x",
  nonce: 2,
  to: "0x68acc3a13441b69016560d23e134c7931bbb27bb",
  transactionIndex: 2,
  value: 3000000000000000000
}

Answer 2

If you have transaction dependencies in your off-blockchain application you should wait until the prior transaction has been mined before submitting the next transaction.

Generally the process is

1. Send a transaction, the result is a transaction hash
2. Busy poll or wait on event to see if the transaction for that hash value was mined.

There aren't good succinct examples of this that I can put into a stackexchange post, but here are some links that show various ways of doing this:

How to tell when your transaction has been mined stack exchange Question

Ether Pudding has this built in, see synchronizeFunction in index.js for how this works. Makes your application code very clean using promises. However index.js is pretty hard to read...just trust me it works ;-)

You can busy poll for the transaction receipt

You can busy poll on the transaction to see if its block is valid. This is what ether-pudding does.

You can create an event filter whose callback fires on every block that's mined, and every time a block is mined you can use one of the above poll methods to see if your transaction was mined. This is possibly better than busy polling, though I've had some issues with the eventing system that are very hard to reproduce.

In all these cases, you don't want to wait forever, you'll want some sort of timeout. Generally in javascript you'll ether fire a callback to your application or return a fulfilled promise when a transaction is mined. I suppose you could use some of the other javascript idioms such as RXJS or Event but I haven't tried those for this purpose.

Answer 3

Do they need to be all at the same time, or can you include an arbitrary delay of say, 30 seconds before the next one fires off? This surely would eliminate any issues of you described. Much shorter times could almost certainly be used.

There is a real possibility of transactions not being sent / processed in the same order and therefore failing but it will depend on supplied gas, level of network activity, how quickly "at the same time" actually is, etc.