Make service error logging configurable

[smagidson]

Currently, there is a fixed set of exceptions that are not logged, another set that are logged as warnings, and everything else is logged as an error (see here). Our particular use-case is that we'd like to make client (4xx) errors like PolicyViolation or a 401 get logged at the info level rather than as errors, since we'd like to cut down on the number of errors we log, and these particular exceptions do not indicate a problem with our service.

More generally, though, it seems like it could be useful to allow users to control how their errors get logged.

I'm willing to make this change, but as I'm not real familiar with the Lagom codebase, I'd appreciate pointers on how best to do this, e.g. how to structure such a configuration, where to pass it in, etc.

In our case, it seems like being able to pass in a lambda that could look at the exception to see if it's a TransportException, and then use the error code to determine the log level, might be a good option.

[TimMoore]

Is this the same as #1091?

[ignasi35]

I think this is also similar to #1375 (currently PR'd in #1398)

[solarmosaic-kflorence]

Strange that this behavior seems to be different in the Java DSL and the Scala DSL:

• https://github.com/lagom/lagom/blob/master/service/javadsl/server/src/main/scala/com/lightbend/lagom/internal/javadsl/server/JavadslServerBuilder.scala#L233
• https://github.com/lagom/lagom/blob/master/service/scaladsl/server/src/main/scala/com/lightbend/lagom/internal/scaladsl/server/ScaladslServiceRouter.scala#L96

Can we at least make these consistent and add BadRequest as a no log to the Scala DSL?

[raboof]

@solarmosaic-kflorence that sounds reasonable to me, could you prepare a PR?

[solarmosaic-kflorence]

@raboof looks like that landed in #2796

[ihostage]

@solarmosaic-kflorence not really. But I think that we can close this issue as a duplicate of #1091.

[solarmosaic-kflorence]

@ihostage by "that" I meant my comment above #1307 (comment)