I was attempting to migrate my standalone mongo server to a single node replica set using the following instructions:
https://docs.mongodb.com/manual/tutorial/convert-standalone-to-replica-set/
Upon restarting the docker container with the -replSet argument and initiating within the mongo shell, I noticed that the replica set was created, but virtually all of my database collections disappeared. The /data/db folder argument hasn't changed and I haven't assigned a different config file. Is there any hope in recovering my data?
Related
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
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:
Get the current config:
cfg = rs.conf()
printjson(cfg)
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]]
Reconfigure the replicaSet only with the available member:
rs.reconfig(cfg, {force : true})
(Don't forget to add the {force:true} option since it is the only way to reconfigure from SECONDARY)
If all is good with this member and it successfully elect as PRIMARY , you can add other new members with rs.add() ...
I have a standlone mongo instance running on AWS and now I created managed replica set using the mongo cloud manager (hosted on AWS as well). No I would like to get my data over from the standalone instance into the replica set if possible without downtime.
Shutting down all services generating a backup of the standalone instance and importing this into the replica set might be the possibility with a downtime.
If I add the standalone node as another replica set member to the new replica set what will happen then? will my standalone instance content be deleted? Or will this be synced to all other replica set hosts as well?
To increase security you need to have 3 systems in replica set (primary, secondary and secondary OR arbiter), having only pri/sec would cause more issues than expected.
if you server (primary) is not started with replica set parameter activated
mongod --replSet "rs0"
then, you need to add entry in config file or add startup parameter --replSet "myReplSet" - and this will cause a breakdown in your service.
then using manual from mongo you can go via steps and initiate single server replica set, then add secondary system.
I was using MongoDB version 2.6.6 on Google Compute Engine and used the click to deploy method.
rs0:SECONDARY> db.createUser({user:"admin", pwd:"secret_password", roles:[{role:"root", db:"admin"}]})
2015-07-13T15:02:28.434+0000 Error: couldn't add user: not master at src/mongo/shell/db.js:1004
rs0:SECONDARY> use admin
switched to db admin
rs0:SECONDARY> db.createUser({user:"admin", pwd:"secret_password", roles:["root"]})
2015-07-13T15:13:28.591+0000 Error: couldn't add user: not master at src/mongo/shell/db.js:1004
I had a similar problem with mongo 3.2:
Error: couldn't add user: not master :
When trying to create a new user, with root role.
I was using only a local copy of mongo.
In my mongod.conf file I had the following uncommented:
replication:
replSetName: <node name>
Commenting that out and restarting fixed the problem. I guess mongo thought it was part of a replication set, and was confused as to who the Master was.
Edit:
I've also found that if you ARE trying to setup a replication set, and you get the above error, then run:
rs.initiate()
This will start a replication set, and set the current node as PRIMARY.
Exit, and then log back in and you should see:
PRIMARY>
Now create users as needed.
I ran into this error when scripting replica set creation.
The solution was to add a delay between rs.initiate() and db.createUser().
Replica set creation is seemingly done in background and it takes time for the primary node to actually become primary. In interactive use this doesn't cause a problem because there is a delay while typing the next command, but when scripting the interactions the delay may need to be forced.
MongoDB will be deployed in a cluster of Compute Engine instances (also known as a MongoDB replica set). Each instance will use a boot disk and separate disk for database files.
Primary and master nodes are the nodes that can accept writes. MongoDB’s replication is “single-master:” only one node can accept write operations at a time.
Secondary and slave nodes are read-only nodes that replicate from the primary.
Your error message looks like you are trying to add the user on the secondary. Try adding the user in the primary.
I ran into this issue when I thought I was running mongo 3.4 but it was mongo 3.6. Uninstalling 3.6 and installing 3.4 fixed my issue.
I have a mongodb installed on windows server. I take regular backups of the data/db folder using Rackspace backup.
I created a deployment of a mongodb replica set with 3 ubuntu servers using Rackspace deployments. Now I want to move the data on windows to the empty replica set. How can I do it?
I tried copying the contents of data/db on windows to var/lib/mongodb on the primary replica set. It didn't work.
For some reason the var/lib/mongodb on the ubuntu machines does not contain data/db directory. When I create a new db the db files are created on var/lib/mongodb directory.
The difference in data directories is fine .. on Windows the default dbpath will be c:\data\db; the Ubuntu package sets the dbpath to /var/lib/mongodb instead.
Since you are starting with an empty replica set (and using a backup from a standalone server), the most straightforward approach would be to:
Stop all the mongod servers for the replica set (you definitely don't want to copy data files directly into a running instance!).
Remove any files that are already in the /var/lib/mongodb data directory.
Copy the data files from your standalone MongoDB backup into /var/lib/mongodb on one of your replica set servers. This server will become your primary to set up the rest of the replica set.
Start up this primary making sure to include a replSet name in your configuration file. You may already have this set from your "empty" replica set that you already created.
Run rs.initiate() in the mongo shell to create the initial configuration on the primary.
Start up your additional servers as members of this replica set: they need the same replSet name configured.
Use rs.add(..) to add your additional servers from the mongo shell on your primary. Assuming the add is successful (i.e. the mongods can connect to each other), this will begin the process of initial sync (copying data from the primary) and the new hosts will become secondaries after they have finishing initial sync.
This is essentially the same steps as the deploy a replica set tutorial, except you are copying over your data first.
The problem could be related to the configuration file of mongodb
locate the file mongodb.conf and edit the dbpath parameter, check if the path really exist, and if it doesn't create the missing directories. Also check permissions in that path
anyway i don't know if its the right way to just copy the datafiles in a new location, i guess you should use mongo import/export
Does anybody knows of a way to add a replica set to a mongo instance which hasn't been started with -replSet and without restarting it ? In other words is it possible to create a replica set and add already running instances of mongodb ?
You need to start mongod with a --replSet parameter (or replSet config file option) in order to use replication. There are replication background tasks and other server internals that are not enabled in standalone mode.
There is no method (as at MongoDB 2.2.0) to change the role of a running mongod instance from standalone to replica set mode (or vice-versa).
In other words is it possible to create a replica set and add already running instances of mongodb ?
As noted, you would need to restart those instances with the replSet parameter.
You can, however, add additional members to a running replica set without downtime.
For more information see the MongoDB manual: Add Members to a Replica Set.