Mongodb sharding – launch mongos with mongos.conf

configurationmongodbsharding

We are currently setting up a sharded cluster with MongoDB, config servers have been set up using a configuration file : mongod.conf pointing out alternative paths for data and logs folders :

systemLog:
   destination: file
   path: "/home/mongo/logs/mongod.log"
   logAppend: true
storage:
   journal:
      enabled: true
      dbpath: "/home/mongo/data"
processManagement:
   fork: true
net:
   bindIp: 127.0.0.1
   port: 27019

sharding:
   clusterRole:configsvr

Using the docs (https://docs.mongodb.org/manual/reference/configuration-options/), I've seen that it is possible to launch mongos using a similar file, problem is, I don't know if this file should be different from mongod.conf. So far I have not seen anyone use a mongos.conf file…

Should the file be identical?
Just changing paths, port and clusterRole?
And adding a "configDB:" lign?

Best Answer

Yes, you use a configuration file for the mongos, and many of the options are the same for the mongos as the mongod. You will need to consult the MongoDB configuration file options documentation for more explicit instructions on which options are viable for which MongoDB server role. I see that you already found that link, but all your answers are there.

When launching the mongos (by hand or in your init script) you feed it the config file as a runtime parameter. You will need to tell the mongos things like what port to run on, the logpath (if you log out), and most importantly configdb=[your config server URIs] and your replica set key.

Related Solutions

Mongodb sharding – Init script for mongos process

You have linked the relevant official request for this in your answer and SERVER-3748 does explain some of the reasons why these don't currently exist.

The most basic reason is that you cannot start mongos without at least one config server being up and working, otherwise it will refuse to start, which makes it a poor candidate for an init script (external dependencies). Generally you want to avoid having services that are going to fail to start when there is no good way to check the reason for failure.

However, it would still be beneficial to give people a script rather than having them modify/write one themselves, hence the Jira issue exists.

The way I would recommend to do this is to base any script off of the existing mongod init script and simply modify it to replace mongod with mongos where appropriate. Here is the current version of that script for Debian:

https://github.com/mongodb/mongo/blob/master/debian/init.d

Things you will need to change:

> DAEMON=/usr/bin/mongos
> DESC=mongos-router
> 
> NAME=mongos
> 
> CONF=/etc/mongos.conf 
> PIDFILE=/var/run/$NAME.pid 
> ENABLE_MONGODB=yes

The advantage to doing this, after you have installed the 10gen package, is that the users will already be set up and you have the mongod script for reference on the system.

You will need to create the config file with appropriate values for your mongos, and there might be a couple of other things you need to tweak - the key is to test before you make anything permanent.

Once you confirm via testing that you have the script working as you wish, then you can add it permanently with update-rc.d

Linux – Enabling WiredTiger engine in MongoDB 3

If I remember correctly, you have to have this in your config:

storage:
    engine: wiredTiger

Though I can't test it right now...

Edit: Found the same suggestion in How to migrate MongoDB 2.6 to 3.0 with WiredTiger

Best Answer

Related Solutions

Mongodb sharding – Init script for mongos process

Linux – Enabling WiredTiger engine in MongoDB 3

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