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If you use containers as part of your day-to-day operations, you need to monitor them -- ideally, by using a docker performance monitoring solution that you already have in place, rather than implementing an entirely new tool. Containers are often deployed quickly and at a high volume, and they frequently consume and release system resources at a rapid rate. You need to have some way of measuring container performance, and the impact that container deployment has on your system. In this article, we’ll take a look at four widely used monitoring platforms—Netuitive, New Relic, Splunk, and AppDynamics—that support containers, and compare how they measure up when it comes to monitoring containers. First, though, a question: When you monitor containers, what kind of metrics do you expect to see? The answer, as we’ll see below, varies with the monitoring platform. But in general, container metrics fall into two categories—those that measure overall container impact on the system, and those that focus on the performance of individual containers.
The first step in any kind of software monitoring, of course, is to install the monitoring service. For all of the platforms covered in this article, you can expect additional steps for setting up standard monitoring features. Here we cover only those directly related to container monitoring. Setup: New Relic With New Relic, you start by installing New Relic Servers for Linux, which includes integrated Docker monitoring. It should be installed on the Docker server, rather than the Docker container. The Servers for Linux package is available for most common Linux distributions; Docker monitoring, however, requires a 64-bit system. After you install New Relic Servers for Linux, you will need to create a docker group (if it doesn’t exist), then add the newrelic user to that group. You may need to do some basic setup after that, including (depending on the Linux distribution) setting the location of the container data files and enabling memory metrics. Setup: Netuitive Netuitive also requires you to install its Linux monitoring agent on the Docker server. You then need to enable Docker metrics collection in the Linux Agent config file, and optionally limit the metrics and/or containers by creating a regex-based blacklist or whitelist. As with New Relic, you may wind up setting a few additional options. Netuitive, however, offers an additional installation method. If you are unable to install the Linux Agent on the Docker server, you can install a Linux Agent Docker container, which will then do the job of monitoring the host and containers. Setup: Splunk Splunk takes a very different approach to container monitoring. It uses a Docker API logging driver to send container log data directly to Splunk Enterprise and Splunk Cloud via its HTTP Event Collector. You specify the splunk driver (and its associated options) on the Docker command line. Splunk’s monitoring, in other words, is integrated directly with Docker, rather than with the host system. The Splunk log driver requires an HTTP Event Collector token, and the path (plus port) to the user’s Splunk Cloud/Splunk Enterprise instance. It also takes several optional arguments. Setup: AppDynamics AppDynamics uses a Docker Monitoring extension to send Docker Remote API metrics to its Machine Agent. In some ways, this places it in a middle ground between New Relic and Netuitive’s agent-based monitoring and Splunk’s close interaction with Docker. AppDynamics’ extension installation, however, is much more hands-on. The instructions suggest that you can expect to come out of it with engine grease up to your elbows, and perhaps a few scraped knuckles. You must first manually bind Docker to the TCP Socket or the Unix Socket. After that, you need to install the Machine Agent, followed by the extension. You then need to manually edit several sections of the config file, including the custom dashboard. You must also set executable permissions, and AppDynamics asks you to review both the Docker Remote API and the Docker Monitoring extension’s socket command file. The AppDynamics instructions also include troubleshooting instructions for most of the installation steps.
As you might expect, there are some significant differences in the metrics which each of these platforms monitors and displays. Output: New Relic New Relic displays Docker container metrics as part of its Application Performance Monitoring (APM) Overview page; containers are grouped host servers when Servers for Linux is installed, and are indicated by a container symbol. The overview page includes drill-down for detailed performance features. The New Relic Servers monitor includes a Docker page, which shows the impact of Docker containers on the server’s performance. It displays server-related metrics for individual Docker images, with drill-down to image details. It does not, however, display data for individual containers. Output: Netuitive Netuitive’s Docker monitor collects a variety of metrics, including several related to CPU and network performance, and almost two dozen involving memory. It also collects computed CPU, memory, and throttling percentages. With Netuitive, you build a dashboard by assembling widgets, so the actual data shown (and the manner in which it is displayed) will depend on your choice of widgets and their configuration. Output: Splunk Splunk is designed to use data from a wide range of logs and related sources; for containers, it pulls data from individual container logs, from Docker and cloud APIs, and from application logs. Since Splunk integrates such a large amount of data at the cloud and enterprise level, it is up to the user to configure Splunk’s analysis and monitoring tools to display the required data. For containers, Splunk recommends looking at CPU and memory use, downtime/outage-related errors, and specific container and application logs to identify problem containers. Output: AppDynamics AppDynamics reports basic container and system statistics (individual container size, container and image count, total memory, memory limit, and swap limit), along with various ongoing network, CPU, and memory statistics. It sends these to the dashboard, where they are displayed in a series of charts.
When it comes to the question of which monitoring service is right for your container deployment, there’s no single answer. For most container-based operations, including Rancher-managed operations on a typical Linux distribution, either New Relic or Netuitive should do quite well. With reasonably similar setup and monitoring features, the tradeoff is between New Relic’s preconfigured dashboard pages and the do-it-yourself customizability of Netuitive’s dashboard system. For enterprise-level operations concerned with integrated monitoring of performance at all scales, from system-level down to individual container and application logs, Splunk is the obvious choice. Since Splunk works directly with the Docker API, it is also likely to be the best option for use with minimal-feature RancherOS deployments. If, on the other hand, you simply want to monitor container performance via the Docker API in a no-frills, basic way, the AppDynamics approach might work best for you. So there it is: Look at what kind of container monitoring you need, and take your pick.