akka-http-2.4.5 instrumentation doesn't apply when using Scala 2.13.x

[jasonjkeller]

When using Scala 2.13.x the akka-http-2.4.5 instrumentation doesn't apply due to this weave violation:

2021-03-25T13:43:37,490+0000 [1 24] com.newrelic FINEST: com.newrelic.instrumentation.akka-http-2.4.5 - 1 violations against classloader jdk.internal.loader.ClassLoaders$AppClassLoader@73d16e93
2021-03-25T13:43:37,490+0000 [1 24] com.newrelic FINEST: WeaveViolation: MISSING_ORIGINAL_BYTECODE
2021-03-25T13:43:37,490+0000 [1 24] com.newrelic FINEST: 		Class: scala/collection/immutable/StringOps
2021-03-25T13:43:37,490+0000 [1 24] com.newrelic FINEST: 		Reason: Could not find original bytecode

The result is that any transactions that are normally started by the Java agent from this instrumentation when akka.http.scaladsl.server.ContextWrapper.apply(AkkaHttpContextFunction.scala) is executed will not exist if using Scala 2.13.x.

The reason that the instrumentation no longer applies is due to refactoring where scala/collection/immutable/StringOps was refactored in Scala v2.13.0-M4 and now is found in scala/collection/StringOps.

The StringOps class wraps the scala implementation of java.lang.String which is scala.Predef.String. It appears that some magic happens behind the scenes where scala Strings are implicitly converted into instances of the StringOps class.

You can see the differences documented here:

• Scala 2.12: https://github.com/scala/scala/blob/2.12.x/src/library/scala/Predef.scala#L132-L138
• Scala 2.13: https://github.com/scala/scala/blob/2.13.x/src/library/scala/Predef.scala#L139-L147

We'll need to build a new version of the instrumentation from the Scala 2.13 dependency.

[jasonjkeller]

I’ve got a branch here that modifies the v6.4.2 agent branch and adds a new instrumentation module named akka-http-2.13_2.4.5 that should apply when using scala 2.13. It needs to be tested and cleaned up a bit before we can get it into an agent release.

v6.4.2...akka-http-2.13_2.4.5

[BoopBoopBeepBoop]

Note that scala convention for jar naming would place the scala major version after an underscore

${name}_${scalaVersion}-${version}-${tag}
ex: server_2.13-0.3.241