When you see the error "EAPI:Invalid nonce" in your Kraken trading bot, it means there is something wrong with the Nonce value.
Explanation of the Kraken error
An EAPI:Invalid nonce error indicates that an API request was received with a repeated or lower than expected nonce value.
Since the nonce value must be unique and must increase with every request, you may run into errors when trying to make simultaneous requests, or requests in rapid succession, or when attempting to use a single API key for multiple devices/apps/bots.
As an example, two simultaneous API requests might not arrive in the intended order, and if the second request (with a higher nonce) arrives before the first request (with a lower nonce), the first request would be rejected when it finally arrives.
As invalid nonce errors will cause your API requests to fail (your orders not to be placed, for example), invalid nonce errors should not simply be ignored, but should be corrected by improving the nonce creation algorithm (see some solutions below).
Solution to the Kraken error
Create multiple API keys:
On Cryptohopper, it's possible to use 2 different API Keys for Kraken. We always recommend using 2 API Keys on Kraken for the best possible trading experience. Always make sure to thoroughly read our tutorial 'How to connect to Kraken with API Keys'. Each API key has its own separate nonce value, so the order in which API requests arrive would no longer be an issue.
Increase the nonce resolution so as to allow additional requests during the same time frame (increasing the nonce resolution from milliseconds to tenths of milliseconds, for example). Cryptohopper recommends using either 1000 or 10000 as the Nonce value.