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Cassandra 3.x High Availability

Cassandra 3.x High Availability

By : Strickland
3.8 (6)
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Cassandra 3.x High Availability

Cassandra 3.x High Availability

3.8 (6)
By: Strickland

Overview of this book

Apache Cassandra is a massively scalable, peer-to-peer database designed for 100 percent uptime, with deployments in the tens of thousands of nodes, all supporting petabytes of data. This book offers a practical insight into building highly available, real-world applications using Apache Cassandra. The book starts with the fundamentals, helping you to understand how Apache Cassandra’s architecture allows it to achieve 100 percent uptime when other systems struggle to do so. You’ll get an excellent understanding of data distribution, replication, and Cassandra’s highly tunable consistency model. Then we take an in-depth look at Cassandra's robust support for multiple data centers, and you’ll see how to scale out a cluster. Next, the book explores the domain of application design, with chapters discussing the native driver and data modeling. Lastly, you’ll find out how to steer clear of common anti-patterns and take advantage of Cassandra’s ability to fail gracefully.
Table of Contents (10 chapters)
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Deleting data


We have established that Cassandra employs a log-structured storage engine, where all writes are immutable appends to the log. The implication is that data cannot actually be deleted at the time a DELETE statement is issued. Cassandra solves this by writing a marker, called a tombstone, with a timestamp greater than the previous value. This has the effect of overwriting the previous value with an empty one, which will then be compiled in subsequent queries for that column in the same manner as any other update.

Garbage collection

Eventually, these tombstones are reconciled with earlier values as part of the compaction process, where the earlier values are discarded. See Chapter 7, Modeling for Availability for more details on how compaction works. There are two possibilities for when data can be physically deleted and tombstones collected.

If a delete occurs while the data is still in the memtable (and therefore, not yet flushed to disk), the existing data will be immediately...

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