Get Started with Apache Cassandra Database in the Cloud

By Jack M. Germain

Linode
Linode
Jul 20, 2017 · 5 min read

If you have not yet keyed into the advantages of running Apache Cassandra, now is as good a time as any to make that introduction. You have four pressing reasons to consider its benefits:

Reason #1: Cassandra gives you more flexibility than a relational database.

Reason #2: Cassandra lets you scale to any number of ongoing users and data volume sizes without becoming sluggish.

Reason #3: Cassandra eliminates worries about issues involving a single point of failure.

Reason #4: Cassandra lets you distribute data among multiple locations, be they data centers or the cloud, or a combination of uses scenarios.

Cassandra is an open-source, Linux-based distributed database. It is a highly scalable, high-performance distributed database with high availability. Its design makes it capable of handling large amounts of data across multiple points.

Another essential benefit of Cassandra is its NoSQL database structure. Why does that matter? As a NoSQL database, it stores and retrieves data other than the tabular relations used in relational databases.

NoSQL databases are schema-free. They support easy replication and have a simple Application Programming Interface or API. All of this bolsters its reliability in handling large amounts of data.

Design Matters

The simple design of NoSQL databases does not mean lightweight or underpowered performance. Design simplicity means greater capability in scaling horizontally. It also means you get better control over data availability.

This simpler design standard permits the use of different data structures than those that are available in relational databases. This makes some operations faster in NoSQL. Ultimately, though, the suitability of a given NoSQL database depends on the problem you use it to solve.

Here is a set of differences between the design that drives a NoSQL database compared to a relational database. Think of a comparison between complex and simple. In this case, simple is superior.

  • NOSQL uses simple query language.
  • NoSQL does not have a fixed schema.
  • NoSQL does not support transactions.

Cassandra’s Features at a Glance

Cassandra operates a peer-to-peer distributed system across its nodes. Cassandra distributes data among all the nodes in a cluster. This is how this type of database is able to manage big-data workloads across multiple nodes without any single point of failure.

That assurance of no single point of failure is a very important factor to consider. Unlike other database types, Cassandra uses one or more of the nodes in a cluster as replicas for a given piece of data.

Why is this important to you? If the database gets an out-of-date value from one or more nodes, Cassandra can plug in the most recent value and execute a read repair function in the background. That results in a reliable and rapid update to the failed values.

Defining Database Terms

If you are a newcomer to databases, the arcane terminology can block your appreciation for Cassandra’s special skill sets. This quick primer on its key components will help clear out the fog of database terminology.

A Node is the location within a database structure that stores its data.

A Datacenter is a collection of related nodes within the database.

A Cluster is a database structure containing one or more data centers.

A Commit log is Cassandra’s crash-recovery mechanism. Every write operation is recorded here.

Mem-tables are memory-resident data structures. After Cassandra makes a commit log, it writes the data to the mem-table. Cassandra creates multiple mem-tables for greater redundancy.

An SSTable is a disk file Cassandra uses to flush the data from the mem-table when its contents reach a threshold value.

A Bloom filter is a nondeterministic algorithm cache for verifying if an element belongs to a particular data set. Cassandra accesses this cache after every query.

Cluster Luster

Clustering is one of Cassandra’s key utilities. It distributes its database over several machines that operate together. Cassandra arranges the nodes into a cluster using a ring format. It then assigns data to them.

The cluster is what makes Cassandra’s design different than other distributed databases. That design is based on a keyspaces structure with three essential attributes. This is the outermost container for data in Cassandra.

One keyspace attribute is having a number of machines in the cluster that hold copies of the same data for replication backup. A second attribute is a series of replica placement strategies that enable Cassandra to place replicas in the ring. The third is a reliance on column families, or a “container” for a collection of rows.

This approach enables a keyspace to function as a container for column families. The column is a basic data structure in Cassandra that has unique functionality.

Each row has ordered columns. Column families within keyspaces hold the structure of stored data. Each keyspace can hold single or multiple column families.

Cassandra’s Columns and Measured Value

Cassandra has two types of columns. Regular columns store data. Super Columns store a map of sub-columns. A column has three values: key (or column name), value, and timestamp.

Cassandra’s column family design differs radically from a table organization in a relational database. A relational table has a fixed model, so columns in a table are rigidly designed and need data. That data can have just a null value. But a data value must exist in every row within each column.

Cassandra’s column families are defined, but Cassandra’s columns are not. Thus, column data can enter any column family at any time. The key difference is that Cassandra does not require individual rows to have all the columns.

Take the Next Step with Cassandra

Now that you have the basics in hand, it’s time to check out Apache Cassandra in more details. That involves downloading the free software and getting some hands-on experience with its documentation guides.

Click to download the latest version of Cassandra, and be sure to follow the download and installation directions. You can check out Apache’s helpful hints and documentation guides here.

Then, take it through its paces using our latest Linode guide on Cassandra.

Please feel free to share below any comments, questions or insights about your experience with Apache Cassandra or databases. And if you found this blog useful, consider sharing it through social media.

About the blogger: Jack M. Germain is a veteran IT journalist whose outstanding IT work can be found regularly in ECT New Network’s LinuxInsider, and other outlets like TechNewsDirectory. Jack’s reporting has spanned four decades and his breadth of It experience is unmatched. And while his views and reports are solely his and don’t necessarily reflect those of Linode, we are grateful for his contributions. He can be followed on Google+.

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