Our MongoDB driver creates a new temporary connection, for every active
connection, to just do a single heartbeat test. There is configurable
delay between every heartbeat test. When the user has an EMQX cluster
with a MongoDB bridge (to a MongoDB replica set), there will be a lot of
connections. Furthermore, as MongoDB creates a log entry every time a
new connection is created, the log will be flooded with info about new
connection. One user have reported more than 1MB of log data in a 10
minute period.
This commit tries to fix this by increasing the default delay between
heartbeats. A better fix would be to change the MongoDB driver so that
it does not create a new connection just to do a heartbeat check, but
this is more complicated so we leave this to the future. We might also
swap out the current MongoDB driver to something better.
Fixes:
https://github.com/emqx/emqx/issues/9851
JimMoen