Book Image

Mastering MongoDB 3.x

By : Alex Giamas
Book Image

Mastering MongoDB 3.x

By: Alex Giamas

Overview of this book

MongoDB has grown to become the de facto NoSQL database with millions of users—from small startups to Fortune 500 companies. Addressing the limitations of SQL schema-based databases, MongoDB pioneered a shift of focus for DevOps and offered sharding and replication maintainable by DevOps teams. The book is based on MongoDB 3.x and covers topics ranging from database querying using the shell, built in drivers, and popular ODM mappers to more advanced topics such as sharding, high availability, and integration with big data sources. You will get an overview of MongoDB and how to play to its strengths, with relevant use cases. After that, you will learn how to query MongoDB effectively and make use of indexes as much as possible. The next part deals with the administration of MongoDB installations on-premise or in the cloud. We deal with database internals in the next section, explaining storage systems and how they can affect performance. The last section of this book deals with replication and MongoDB scaling, along with integration with heterogeneous data sources. By the end this book, you will be equipped with all the required industry skills and knowledge to become a certified MongoDB developer and administrator.
Table of Contents (13 chapters)

Locking in MongoDB

Document- and collection-level locking is mentioned throughout this chapter and also in several other chapters in this book. It is important to understand how locking works and why it is important.

Database systems use the concept of locks to achieve ACID (atomicity, consistency, isolation, durability) properties. When there are multiple read or write requests coming in in parallel, we need to lock our data such that all readers and writers have consistent and predictable results.

MongoDB uses multi-granularity locking. The available granularity levels in descending order are as follows:

  • Global
  • Database
  • Collection
  • Document

The locks MongoDB and other databases use are the following in order of granularity:

  • IS: Intent shared
  • IX: Intent exclusive
  • S: Shared
  • X: Exclusive

If we use locking at a granularity level with shared (S) or exclusive (X), then all higher...