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sreweekly/markdown/271/05-what-is-observability.md

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+# What is Observability
+
+- **期号**: SRE Weekly Issue #271（2021-05-23）
+- **作者**: Brendan Gregg
+- **链接**: http://www.brendangregg.com/blog/2021-05-23/what-is-observability.html
+
+## 简介
+
+A new spin: this one makes the distinction between “experimental tools” that affect the state of the system, and “observability tools” that are read-only.
+
+## 正文
+
+It's a made-up computer word that my word processor decorates with a wiggly red you-can't-spell line. At least it did until I clicked "Add to Dictionary" (it got too annoying as I was writing a book on computer observability). Some people abbreviate it as o11y.
+
+Observability: The *ability* to *observe*.
+
+Observe-ability. Observability.
+
+In computer engineering we use it to describe the tools, data sources, and methods for understanding (observing!) how a technology is operating. We don't use the *real* word "observable" since that implies the wrong thing. Imagine "observable metrics": Are there metrics that *aren't* observable?
+
+Using observability in sentences:
+
+- What observability tools are installed? (Means: What tools exist that only read state?)
+- What observability does that database have? (Means: What metrics and logs does it have?)
+- How do you do observability? (Means: What products do you use for metrics, tracing, etc.?)
+- Let me try some observability first. (Means: Let me look at the system without changing it.)
+
+Wait, aren't all performance tools observability tools? No. *Experimental* tools change the state of the system to understand it. For example, benchmarks.
+
+As an analogy, a car's dashboard is a collection of observability tools that let you understand how the car is operating (speed, rpm, temperature). A car's 0-60 mph time is an *experiment*.
+
+When I was a performance consultant I'd show up to random companies who wanted me to fix their computer performance issues. If they trusted me with a login to their production servers, I could help them a lot quicker. To get that trust I knew which tools looked but didn't touch: Which were observability tools and which were experimental tools. "I'll start with observability tools only" is something I'd say at the start of every engagement.
+
+Note that observability tools aren't completely harmless: Their execution consumes resources, usually negligible, but in some cases it's enough to perturb the target of study. This is the "observer effect."
+
+Another use of the term observability is as a reminder to switch between tool types, and not to get stuck on one. A colleague (Roch Bourbonnais from memory) once told me:
+
+"You have two hands. Observability and experimentation."
+
+It stuck with me as it also makes the point that when you're only using one type to solve a performance problem **you're working one-handed**.
+
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