Yes, your FTDC collects diagnostic data, and the BSON document generated during that process exceeded the 16MB BSON limit, which is why you’re seeing the BSONObjectTooLarge error. This typically happens when FTDC attempts to serialize a very large internal diagnostic document.
It’s unclear exactly what’s causing the large BSON object without more detailed logs, but you can enable command-level logging in MongoDB to get more granular visibility into which commands and metrics may be contributing to this. You can do that by setting the following in your config or as a runtime parameter:
YAML:
setParameter:
logLevel: 1
logComponentVerbosity:
verbosity: 0
command:
verbosity: 1
Once you identify the source of all the excessive diagnostic logs, you can tune or disable it if neccesary.