Hi,
There is an opened ticket in akka-http regarding exceptions being thrown
after using HttpEntity.toStrict:
https://github.com/akka/akka-http/issues/1177.
My question is regarding Johannes Rudolph's comment about it being a
workaround:
Using toStrictEntity is basically only a workaround and not a solution
> because it will mean that all entity data will be buffered in memory which
> means that your server will need more memory per concurrent request than
> necessary.
Let's say you have the need to log the complete request payload of all
requests coming in to a service. If you want to allow the logging logic to
fully consume to request payload and still allow the entity to be
unmarshalled to the desired object later on, what would be another way to
ensure this never fails other than using toStrict, forcing the entire
payload into memory and allowing it to be consumed more than once?
For example, consider the following route:
val route = extractExecutionContext & extractMaterializer & extractLog {
(ec, mat, log) =>
logRequest(LoggingMagnet(_ => logRequestDetails(_)(ec, mat, log))) {
path("someapi") {
post {
entity(as[SomeInputClass]) { input =>
// do something with input
}
}
}
}
}
def logRequestDetails(req: HttpRequest)(implicit ec: ExecutionContext,
materializer: Materializer, log: LoggingAdapter): Unit =
Unmarshal(req.entity).to[String].map(b => s"The request body is
$b").onComplete {
case Success(s) => log.info(s)
case Failure(e) => log.error(e, "Error")
}
This is obviously a contrived example, but this logs the request body. It
works, but we've seen such a pattern inconsistently yield
java.lang.IllegalStateException:
Substream Source cannot be materialized more than once errors. Isn't this a
case where converting to a strict entity the correct way to address such
problems, i.e. allow the request entity to be consumed more than once? If
not, what would be the correct way?
Thanks for any insight you might have!
Yannick
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