Keepers can get stuck in an infinite loop if they run out of gas

[ghost]

If a keeper wants to sends 4 transactions at once (could be a sai-maker-otc keeper with a few bands configured) but the ETH available in its account is enough to send only lets say three of them, the keeper can get infinitely stuck.

The reason of it is that web3.eth.sendTransaction will not immediately fail for the fourth transaction if they all will get sent almost at the same time, although Parity will silently reject it with a Transaction marked invalid (hash .....) message appearing in console. As the rejection is silent (web3.eth.sendTransaction seemed to be successful from the keeper point of view), the keeper will infinitely wait for that transactions receipt to appear, which will never happen. This will make it stuck forever.

[ghost]

Hmm.. maybe calling a getTransactionByHash(...) to check if that transaction is still in the pool...?