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.
Related
I tried to search but most of the solutions are very old, and I feel there will be a better solution available which I am unable to find.
Problem
I created the replica set, and it's working. I tried to connect my docker backed application, and it was connecting to it.
Later I changed the dbpath from dbpath=/var/lib/mongodb to the new path dbpath=/data/mongodb. I didn't restart the replica set after this change.
I ran my backend application and it couldn't connect to the replica set. I think its because I didn't restart the MogoDB ReplicaSet. I am using Mongo version 4.4.5
I want to restart the MongoDB Replica Set to check if this can solve the issue.
My connection string :
mongodb://username:pwd#prod-privateIP-1:27017,prod-privateIP-2:27017,prod-privateIP-3:27017/prodDB?replicaSet=replica1&authSource=admin
What is the best practice/recommended approach to restart the MongoDB Replica Set ?
Is there any ways or methods to start mongodb replication directly when mongod service start? I don't want to enter to shell and ON the replication?
Thanks!
You can create a mongod service which starts automatically when server starts.
First you need to create a configuration file(mongodb.conf) which will include configuration settings such as replicaSet name etc. Then create a service and install it using following command
mongod -f c:\mongod.conf --install
Then start the service using
net start mongodb
Read about configuration file here and
How to install mongo as service here
When you create a valid replica set in mongodb, your data will be asynchronously from the primary member to the secondary members in replica set
Having said that, you're not required to do extra efforts manually to get data replication done
When you do rs.slaveOk() on secondary, that allows you to query data from secondary members in the replica set.
It's a provision. It allows you to read from secondary provided that you're can tolerate the possible eventual consistent data. The replication does not happen when you do rs.slaveOk() on secondary
I'm not sure to understand. Your question was about service start. On my part, I install mongo on ubuntu and the service is not started with replicatet mode.
Finally, I disabled the first one and I created another service with the option --replSet myReplicat .
When you have only 2 servers, there is a problem with majority votes. On my part, I had 2 secondary after I stopped the primary and it was difficult to comeback with 1 primary and 1 secondary.
Effectively, the replication is always active. By default, all connections should go to the Primary. If you want to readonly from a secondary, you first enter the commande rs.slaveOk(). This command is active at session level. If you reconnect, you have to pass it again. It is not possible to put it at server side.
I have two standalone nodes, which have mongodb running on them. Both of them have a replica set configuration rs0 and start with rs.initiate().
But in some scenarios, I want them to run as individual nodes, but in some cases, I want one to become primary and one to become secondary. But since I have done rs.initiate() on both, I won't be able to add any node as secondary.
So is there a way to undo the replica set configuration so that I can enable adding the secondary node.
Follow these steps
Switch to local database
Execute the command to make the cllection such as system.replset empty
db.system.replset.remove({});
Make sure that system.replset in local database is empty by executing the following command:
db.system.replset.find();
Refernce from : https://vitalflux.com/mongodb-how-to-reset-mongo-replica-set/
you can simply prepare a new config document and reconfigure the replication.
rs.reconfig(new_config_file)
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.
We have a mongoDB replica set which has 3 nodes;
Primary
Secondary
Arbiter
Somehow our replica set has ended up with 1 & 2 both being set as secondary members. I'm not sure how this has happened (we have had a server migration which one of the nodes runs on, but only one).
Anyway, I've been trying to re-elect a new primary for the replica set following the guide here
I'm unable to just use
rs.reconfig(cfg)
as it will only work if directed at the primary (which I don't have).
Using the force parameter
rs.reconfig(cfg, { force: true})
would appear to work but then when I requery the status of the replica set, both servers are still only showing as Secondary.
Why hasn't the force reconfig worked? Currently the database is locked out whatever I try.
1.Convert all nodes to standalone.
Stop mongod deamon and edit /etc/mongod.conf to comment replSet option.
Start mongod deamon.
2.Use mongodump to backup data for all nodes.
Reference from mongo docs:
https://docs.mongodb.com/manual/reference/program/mongodump/
3.Log into each node, and drop local database.
Doing this will delete replica set config on the node.
Or you can just delete a record in collection system.replset in local db, like it said here:
https://stackoverflow.com/a/31745150/4242454
4.Start all nodes with replSet option.
5.On the previous data node (not arbiter), initialize a new replica set.
6.Finally, reconfig replica set with rs.reconfig.