APM and observability are techniques organizations can use to assess an application's health and provide a good user experience. However, these tools work in completely different ways.
What is APM?
As its name suggests, application performance monitoring (APM) is a tool to locate the source of application performance issues. Even so, APM goes well beyond what might be expected from basic performance monitoring offerings.
APM is often used with a modern application as a way of assessing the user experience. At a general level this might mean tracking an application's load, along with KPIs. Doing so not only enables an organization to monitor the user experience; it also provides visibility into how that experience changes as an application's workload increases.
Some DevOps teams incorporate APM into the application development process to avoid putting a change into production if it's found to adversely affect performance.
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There are many other aspects of APM, besides providing insight into the user experience. Some APM tools, for example, help with root cause analysis. Modern applications tend to be extremely complex and might span multiple systems, so an issue with any one of these systems can result in an overall system performance problem. Other APM tools map all the components and infrastructure an application relies on. When performance problems occur, the APM tool can compare real-time metrics with historical telemetry data to figure out where the problem resides.
What is observability?
Like APM, observability is a method used to determine the overall health of complex systems and IT workloads. While APM collects data for KPIs, observability aggregates data from various sources to paint a picture of the system's overall health.
Observability uses three main data sources that are often referred to as the pillars of observability.
- Metrics. These generally refer to raw performance data. Metrics might represent anything from the number of CPU cycles being consumed at a given moment to the amount of time an e-commerce application takes to complete a credit card transaction.
- Traces. These help to monitor the interaction between the components making up a complex system. A network trace, for instance, can track the path packets take to their destination. An application trace can also track how the application's components are used.
- Logs. Coming in many forms, logs can be informational or contain errors or warnings. An informational log entry might be generated, for example, when a process is created, while an error event might be added to a log if that process were to terminate unexpectedly.
What are the differences between APM and observability?
APM and observability tools can ensure a good user experience, but they work toward that goal in different ways. Observability takes the data that exists in logs, metrics and traces, and then uses that information to form an overall health assessment. Even though the goal is to ensure a good user experience, observability doesn't directly focus on gauging the user experience. Instead, observability applies the principles of control theory, which essentially state that it's possible to understand what's going on with a system by examining its inputs and outputs. Examining logs, metrics and traces collectively enables a tool to assess the application's health, which can then be used to determine if users are having a good experience.
APM works by actively collecting internal state data and data related to application response time. This data correlates directly to the user experience. Some APM tools are designed to monitor the underlying infrastructure in addition to the application itself, which enables the tool to perform root cause analysis when problems occur.
Why APM and observability are both important
Monitoring and observability are undeniably important, but they serve two different purposes. Observability can loosely evaluate the user experience, but it tends to focus more heavily on an application's health. And while observability isn't always the best tool for tracking the user experience, it can be used proactively to detect and remediate issues before they become problematic.
APM focuses on the user experience. Some APM tools even focus on monitoring the user experience in specific situations, such as virtual desktop environments.
It's worth noting that APM and observability are often used together. For example, troubleshooting tools designed for root cause analytics often rely on APM monitoring techniques. They might also incorporate observability tools, such as log entries, to gain a more complete picture of what's going on with a system.
For more information on APM and observability, read Using AI and machine learning for APM and 7 principles of observability in modern applications.