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.
Related
We are using mongodb cluster with set of 3 members , and all consumers are able to read/write data.
Use mongo.conf file to create cluster && configure replica set, which are executed in ansible script as part of system restart.
Our system does heavy writes/read operation on mongo clusters ,and sometime replica get broken.
Then it is no longer feasible to restore replica without deleting data from one of the corrupted server.
Here are my queries:
what is better way to notify when replica is broken using script/some code?We can not use Mongo atlas
etc.
What is efficient way to restore data on corrupted member.
What is better way to notify when replica is broken using script/some code?
Use the replSetGetStatus database command.
You can run this command from any driver or the shell. Among other things, it returns the state (primary/secondary/startup/recovery/unreachable) and last applied operation time for each member.
What is efficient way to restore data on corrupted member.
Check out the docs for a few options: https://docs.mongodb.com/manual/tutorial/resync-replica-set-member/#resync-a-member-of-a-replica-set
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.
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.
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.