Observability

If you have worked with any APMs (or other monitoring/observability products) under Java, you might have heard something like: [paraphrased-marketing-text] to track everything from performance issues to errors within your application, just attach the Java Agent to your app and all of your problems are gone [/paraphrased-marketing-text].

You can read things like this in product docs, or blog posts or hear from sales, marketing, and even in conference talks. What I think you can hear less are the trade-offs, so let’s dive a little bit into that.

In mathematics, cardinality is the measure of the number of elements (distinct values) of a set. For example, the set {200,404,503} contains 3 elements so the cardinality of it is 3. But what does “High Cardinality” have to do with (time series) metrics? Glad you asked, the answer is everything. :)