MongoDB Server Administration

Tuesday. February 20, 2018 - 3 mins

MongoDB Server Administration

The intention of this document is to share a brief overview of relevant concepts and internal knowledge necessary to administer and debug server side issues

Similar to the process for application code changes, server configurations and changes should also be reviewed by one or more core contributor.

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mongod process

mongod is the primary daemon process for the MongoDB system. It handles data requests, manages data access, and performs background management operations.

Basic upstart operations:

• check status: sudo service mongod status
• start: sudo service mongod start
• stop: sudo service mongod stop
• restart: sudo service mongod restart

Configuration

Location of ubuntu upstart config file: /etc/mongod.conf

data : /data/db mongod logs: /log/mongod.log

Useful mongo shell commands to manage Replica Set

Connect to the primary of the replica set and on the mongo shell type

• Check if the current instance is master: rs.isMaster()
• Check current status: rs.status()
• Examine configuration: rs.conf()
• Add a replica set member: rs.add("host:port")
• Remove a replica set member: rs.remove("host:port")
• Get the build version (for SOC2 questions) db.runCommand( { buildInfo: 1 } )

More commands

Replication

Replication helps provide redundancy, improve data availability Some important design decisions and tradeoffs:

• Chain replication - enable or disable?
• Optional Arbiter, number of data bearing nodes
• Consistency requirements: ..WriteConcern : j, w ..ReadConcern : local ,majority, linearizable NOTE To use majority, replication.enableMajorityReadConcern should be true.

For more information on replication please see the official documentation

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Managing Roles

Official Link

Authentication

Follow the documentation here to enable authentication in a replica set.

Converting a Standalone to a Replica Set

Follow instructions here

Cloud Manager

Cloud Manager is a service to manage, monitor, backup and configure alerts for a MongoDB deployment.

To use this service, ask a Project Owner to add you as a user.

Alerts

See official documentation here

Backups

See official documentation here

Backup Agents

See official documentation here

Monitoring Agents

See official documentation here

MongoDB 3.4 features

• Starting with MongoDB 3.4, it is possible to enable authentication without downtime. See this for more details.

• There are some new features like Views which could be useful to standardize SQL like joins across collections. But enabling these should be done with prior approval of #tech since some of these are backwards incompaitible

Provisioning a box

Ideally, this would be an automated step that very few people should care about.

In case you end up doing this step manually, some things to remember are:

• Security groups
• Storage: Make sure you allocate enough disk space and additional EBS volumes as needed.
• Make sure the volumes are mounted otherwise the additional volumes won’t be used.
• Storage: WiredTiger ( Mongo’s storage engine ) highly recommends using XFS Read this to get a sense of the performane difference with ext4

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Nikhil Raju

A Data Scientist who strongly believes good software engineering practices are essential to the success of any machine learning project

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