There is no 'automatic' built in way to recover from a crash. A crash could occur from a power failure - for example.
You could add a node between each of your current nodes, that store the msg.payload and the curent location to a file. Then if there is a crash, at startup you would check the file and restore the msg and start at that location.
so an HTTP request comes in and is passed to the first node 'A' - put in a node between HTTP-in and 'A' to write out the msg and the location 'A-in'. Node 'A' finished and passes on to node 'B' - put in a node between HTTP-in and 'B' to write out the msg and the location 'B-in' etc, etc
When ever NR starts you have a node that checks the file and it it sees a msg and 'B-in' it passes the msg to 'B'.
But what happens if the system crashes while the 'backup' node is running or while it is writting out the file? or what happens it it crashes while processing in the first node before sending out the HTTP response? or how about it is still in the first node and has sent the HTTP response, should that node be restarted and is it ok to send out the HTTP response again? Or what happens if after restarting and while reading the file it crashes again. Or the file becones corrupted or...
there are probably many other conditions that all depend on what you are doing, how critical the data is and other factors that only you know and can determine, but I hope I've given you some ideas and things to think about.