Hi:
I ran into a problem with our mongodb when balancer is performing move chuck among the shards.
Our application sometimes hang for few minutes when it creates an object into a gridfs db. I saw in the db log the recently created object id went into chuck migration as soon as it was inserted. The app went into pause mode (no cpu usage) until chuck migration is completed, the application resumes itself.
I stopped the balancer manually for now. No more application hang during object creation.
So somehow the sharding action on move chunk on the db is causing the app went into pause mode.
I want to see if you guys out there has any suggestion on where I should check for the application hang?
My mongo version: 3.6. I know 
Thanks in advance.
Eric