Error Premature EOF

Cause

The error is usually produced when working with Attachment object and the job reaches a query time out on Salesforce side (2 minutes). Salesforce stops the job while dataloader.io is waiting for the data which is truncated and therefore the Premature EOF (End Of File) error is reported.

Solution

To avoid this error the query should be simplified so it can be processed faster.

Please, notice that sometimes the query does not have too much complexity but in case your SF org has a big number of attachments and your query doesn't have any condition but the LIMIT option is used to reduce the number of exported records this can easily reach the query time out.

In that case you should apply filters to reduce the queried number of records instead of using the LIMIT option. You can use for example the CreatedDate field to filter the number of Attachments.

This can also happen if the number of exported Attachments is too big. Notice that usually the number of Attachments that are exported successfully is around 2000 per task run (this is not a limit set on dataloader.io side but what usually avoids reaching some other limitation on Salesforce API).