Question

The mongo shell includes a useful print command.

When executing map_reduce from pymongo, how can one print / log info from within a javascript block?

Update: OK, I have an answer. The process running mongo will output whatever is printed with print(). A second option is to configure mongo logging (and probably tailing the log files). Virtual bonus points for answering “Can I still get these values directly in python via pymongo?”

Answer 1

You can still use print() inside the JS block which will get written to /var/log/mongodb/mongodb.log, more info here. Due to the fact that map/reduce happens server-side it won’t emit anything in your Python application.