Recently because of an unknown issue our MongoDB hosted on a GCP compute VM has stopped, we were unable to restart it because it's throwing MongoDB.service is not found. so we reinstalled the MongoDB after taking a backup of all .wt files in the DB path. once we've reinstalled the MongoDB we copied the files back and we can't see the data in the DB. we tried the --repair flag but still no use. is there a way we can get this working?

The other thing is we've taken the VM snapshot from the day before the crash. there we can see the data in MongoDB only if we run the method rs.slaveOk(). I think we can't use that DB as the primary db. is there a way that we can use this as a primary db.

I'm relatively new to the concept of replica set, Master/slave any suggestions and questions are welcome

Thanks

CodePudding user response：

If you see the data from the snapshot with rs.slaveOk() it is easy to recover , you can reconfigure the member as standalone PRIMARY with this steps:

1. Get the current config:

   cfg = rs.conf()
   printjson(cfg)
   

2. Set in the temp variable cfg only the available member(in the example it is the first in the cfg with id:0 ):

   cfg.members = [cfg.members[0]]
   

3. Reconfigure the replicaSet only with the available member:

   rs.reconfig(cfg, {force : true})
   

( Dont forget to add the {force:true} option since it is the only way to reconfigure from SECONDARY )

4. If all is good with this member and it successfully elect as PRIMARY , you can add other new members with rs.add() ...