Mongodb – Create a second Replica set on same 3 nodes as another Replica set

mongodb

Can a second 3 node Replica set be installed on the same 3 nodes with another 3 node Replica set without interference?

Best Answer

Yes, for testing and development. Not for production, obviously. Note below, the different port numbers and data paths for each mongod instance.

If you had the first replica set like this:

mkdir -p /srv/mongodb/rs0-0 /srv/mongodb/rs0-1 /srv/mongodb/rs0-2

mongod --port 27017 --dbpath /srv/mongodb/rs0-0 --replSet rs0 --smallfiles --oplogSize 128 --fork

mongod --port 27018 --dbpath /srv/mongodb/rs0-1 --replSet rs0 --smallfiles --oplogSize 128 --fork

mongod --port 27019 --dbpath /srv/mongodb/rs0-2 --replSet rs0 --smallfiles --oplogSize 128 --fork

You could add a second replica set like this to the same localhost with the following:

mkdir -p /srv/mongodb/rs1-0 /srv/mongodb/rs1-1 /srv/mongodb/rs1-2

mongod --port 37017 --dbpath /srv/mongodb/rs1-0 --replSet rs1 --smallfiles --oplogSize 128 --fork

mongod --port 37018 --dbpath /srv/mongodb/rs1-1 --replSet rs1 --smallfiles --oplogSize 128 --fork

mongod --port 37019 --dbpath /srv/mongodb/rs1-2 --replSet rs1 --smallfiles --oplogSize 128 --fork

Reference: Deploy a Replica Set for Testing and Development

Related Solutions

MongoDB – Admin DB Replication in Replica Set

There are a couple of separate questions/issues here:

do you have to create that same user on nodes 2/3?

If they are members of the same replica set, then no. The users will be written to the primary and then replicated to the secondaries - remember any secondary can become primary in a normal set, so you would have to have all the data necessary to do that, including users. If the nodes are in the set when they are added, the users will replicate normally. If you add them later, they will replicate the users as part of the initial sync process.

Note that for nodes that are members of different replica sets (say multiple shards) that is not the case.

I'm having some trouble doing that if I bring up the other nodes with auth/keyfile turned on

Remember that the keyfile must be identical for all nodes in a set. The keyfile is what the nodes will use to authenticate with each other (for the purposes of initial sync and replication for a start, so it is an absolute must). If you are having issues when you add the nodes, there will be errors in the logs that will tell you why. The common reasons would be:

Incorrect config (new nodes not configured with the replica set name)
Different key files (this must be identical on all nodes in the replica set)
Connectivity or hostname lookup issues

If you expand on the difficulties you have when you try to add (how you are adding, what error you get, and preferably the output of rs.status() and a sample config file) I can elaborate further.

MongoDB MMS – Same Alias for Two Data Nodes of Different Shards

From the MMS Dashboard; what is the MMS Agent Log saying?

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Have you looked in the mms-monitoring agent log locally on the server?

/var/log/mongodb-mms/monitoring-agent.log

Update

Please add a screen shot of how you are configuring the host

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Update 14:02

Can you ping S143, S144 and mongo-client2 from the server where the mms-agent is installed?

Can you telnet to those servers from the mms-agent machine?

telnet S143 37007
telnet S144 37007
telnet mongo-client2 37007

If you can't, then perhaps there is a network problem between the server with the MMS agent and the three mongods you listed above.

Best Answer

Related Solutions

MongoDB – Admin DB Replication in Replica Set

MongoDB MMS – Same Alias for Two Data Nodes of Different Shards

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