Docker Cookbook

Chapter 9. Monitoring Containers

9.0 Introduction

When operating distributed systems and distributed applications, you need access to as much information as possible. You will never need to monitor a large number of resources, extract trends, and trigger alerts. You will also need to collect logs from all processes running in containers and aggregate those logs in data stores for further indexing and searching. Finally, you will need to visualize all this information to quickly navigate your application and debug it if need be.

This chapter starts with some Docker commands that give you basic debugging tools that you can use in small-scale deployments or when you have to dive deeper into a specific container. Recipe 9.1 introduces the docker inspect method that gives you all the information about a container of an image. Recipe 9.2 shows you how to use docker stats to get a stream of resource usage for a specific container. Finally, Recipe 9.3 presents docker events, which listens to Docker events on a particular host. These capabilities are available through the Docker API and hence can be used through any Docker client that supports them.

As you build your application you will want to collect the logs of your services running in containers. This is not specifically monitoring, but logs can be used to derive new metrics that you need to monitor. Docker provides a simple mechanism to look at stdout of the foreground process running in a container, Recipe 9.4. You can also redirect ...