Book Image

Learn MongoDB 4.x

By : Doug Bierer
Book Image

Learn MongoDB 4.x

By: Doug Bierer

Overview of this book

When it comes to managing a high volume of unstructured and non-relational datasets, MongoDB is the defacto database management system (DBMS) for DBAs and data architects. This updated book includes the latest release and covers every feature in MongoDB 4.x, while helping you get hands-on with building a MongoDB database app. You’ll get to grips with MongoDB 4.x concepts such as indexes, database design, data modeling, authentication, and aggregation. As you progress, you’ll cover tasks such as performing routine operations when developing a dynamic database-driven website. Using examples, you’ll learn how to work with queries and regular database operations. The book will not only guide you through design and implementation, but also help you monitor operations to achieve optimal performance and secure your MongoDB database systems. You’ll also be introduced to advanced techniques such as aggregation, map-reduce, complex queries, and generating ad hoc financial reports on the fly. Later, the book shows you how to work with multiple collections as well as embedded arrays and documents, before finally exploring key topics such as replication, sharding, and security using practical examples. By the end of this book, you’ll be well-versed with MongoDB 4.x and be able to perform development and administrative tasks associated with this NoSQL database.
Table of Contents (22 chapters)
Section 1: Essentials
Section 2: Building a Database-Driven Web Application
Section 3: Digging Deeper
Section 4: Replication, Sharding, and Security in a Financial Environment
Working with Complex Documents Across Collections

Adding shards to the cluster

To create a sharded cluster, you need to add servers configured as shard servers under the following conditions:

  • You need to open a mongo shell on a mongos instance that's been configured for the sharded cluster you are building.
  • You need to have been granted the appropriate cluster administration role (

The shell command to add a shard is sh.addShard(). Here is the generic syntax:


REPLICA_SET represents the name of the replica set hosting the shard. MEMBER is the DNS or resolvable hostname of the replica set member. PORT defaults to 27018 (not the same as a standalone mongod instance)!

If sharding has been enabled for the database, when you execute sh.addShard(), the sharded cluster balancer immediately starts moving chunks to the new shard. Be prepared for a high initial volume of database...