A Primer on Building a Monitoring Strategy for Amazon RDS

In a previous blog post, we talked about Amazon Relational Database Service (RDS). RDS is one of the most popular cloud-based database services today and extensively used by Amazon Web Services (AWS) customers for its ease of use, cost-effectiveness and simple administration.

Although as a managed service, RDS doesn’t require database administrators (DBAs) to do many of the day-to-day tasks, it still needs to be monitored for performance and availability. That’s because Amazon doesn’t auto-tune any database performance — this is a shared responsibility of the customer.

That’s why there should be a monitoring strategy and processes in place for DBAs and operation teams to keep an eye on their RDS fleet. In this blog post, we will talk about an overall best-practice approach for doing this.

Why Database Monitoring

Keeping a database monitoring regimen in place, no matter how simple, can help address potential issues proactively before they become incidents, and cost additional time and money. Most AWS infrastructure teams typically have decent monitoring in place for different types of resources like EC2, ELB, Auto Scaling Groups, Logs, etc. Database monitoring often comes at a later stage or is ignored altogether. With RDS, it’s also easy to overlook due to the low-administration nature of the service. The DBA or the infrastructure managers should therefore invest some time in formulating and implementing a database monitoring policy.

Please note that designing an overall monitoring strategy is an involved process and is not just about defining database counters to monitor. It also includes areas like:

• Service Level Agreement
• Classifying incident types (Critical, Serious, Moderate, Low etc.)
• Creating RACI (Responsible, Accountable, Consulted, Informed) matrix
• Defining escalation paths etc..

A detailed discussion of all these topics is beyond the scope of this article, so we will concentrate on the technical part only.

What to Monitor

Database monitoring, or RDS monitoring in this case, is not about monitoring only database performance. A monitoring strategy should include the following broad categories and their components:

While many of these things can be monitored directly in AWS, Sumo Logic can greatly help with understanding all of the logs and metrics that RDS produces.

In this article, we will talk about what AWS offers for monitoring RDS. As we go along, we will point out where we think Sumo Logic can make the work easier.

Monitoring Amazon CloudWatch

You can start monitoring RDS using metrics from Amazon CloudWatch. Amazon RDS, like any other AWS service, exposes a number of metrics which are available through CloudWatch. There are three ways to access these metrics:

• From AWS Console
• Using AWS CLI
• Using REST APIs

The image below shows some of these metrics from the RDS console:

Amazon CloudWatch shows two types of RDS metrics:

• Built-in Metrics
• Enhanced Monitoring Metrics

Built-in Metrics

These metrics are available from any RDS instance. They are collected from the hypervisor of the host running the RDS virtual machine. Some of the metrics may not be available for all database engines, but the important ones are common.

It is recommended the following RDS metrics are monitored from CloudWatch

Amazon RDS Aurora engine also exposes some extra counters which are really useful for troubleshooting. At the time of writing, Aurora supports MySQL and PostgreSQL only. We recommend monitoring these counters:

You can use the AWS documentation for a complete list of built-in RDS metrics.

Enhanced Monitoring Metrics

RDS also exposes “enhanced monitoring metrics.” These are collected by agents running on the RDS instances’ operating system. Enhanced monitoring can be enabled when an instance is first created or it can be enabled later. It is recommended enabling it because it offers a better view of the database engine.

Like built-in metrics, enhanced metrics are available from the RDS console. Unlike built-in metrics though, enhanced metrics are not readily accessible from CloudWatch Metrics console. When enhanced monitoring is enabled, CloudWatch creates a log group called RDSOSMetrics in CloudWatch Logs:

Under this log group, there will be a log stream for each RDS instance with enhanced monitoring. Each log stream will contain a series of JSON documents as records. Each JSON document will show a series of metrics collected at regular intervals (by default every minute). Here is a sample excerpt from one such JSON document:

It’s possible to create custom CloudWatch metrics from these logs and view those metrics from CloudWatch console. This will require some extra work. However, both built-in and enhanced metrics can be streamed to Sumo Logic from where you can build your own charts and alarms. Regardless of platform, it is recommended to monitor the enhanced metrics for a more complete view of the RDS database engine.

The following counters should be monitored for Amazon Aurora, MySQL, MariaDB, PostgreSQL, or Oracle: