MetricsOps

Given an exclude function, return a 'classifier' function, i.e. for application in org.http4s.server/client.middleware.Metrics#apply.

Let's say you want a classifier that excludes integers since your paths consist of:

• GET /users/{integer} = GET_users_*
• POST /users = POST_users
• PUT /users/{integer} = PUT_users_*
• DELETE /users/{integer} = DELETE_users_*

In such a case, we could use:

classifierFMethodWithOptionallyExcludedPath( exclude = { str: String => scala.util.Try(str.toInt).isSuccess }, excludedValue = "*", intercalateValue = "_" )

Chris Davenport notes the following on performance considerations of exclude's function value:

It's worth noting that this runs on every segment of a path. So note that if an intermediate Throwables with Stack traces is known and discarded, there may be a performance penalty, such as the above example with Try(str.toInt). I benchmarked some approaches and regex matches should generally be preferred over Throwable's in this position.