Response entity was not subscribed after 100 seconds. Make sure to read the response entity body or call `discardBytes()` on it - scala

Question

I am building a scala application. Within the application, we are making a call to an external service, and fetching the data.
When I am hitting the endpoint of this external service using the
postman, I am getting the complete data, around 9000 lines of JSON
data, within 9 seconds.
But when I am hitting the same endpoint through my scala application, I am getting a 200 OK response, but getting the below error:
[WARN] [06/09/2022 18:05:45.765] [default-akka.actor.default-dispatcher-9] [default/Pool(shared->http://ad-manager-api-production.ap-south-1.elasticbeanstalk.com:80)] [4 (WaitingForResponseEntitySubscription)] Response entity was not subscribed after 100 seconds. Make sure to read the response entity body or call `discardBytes()` on it. GET /admin/campaigns Empty -> 200 OK Chunked
I read about it and found that we can set response-entity-subscription-timeout property to a higher value. I set it to about 100 seconds, but this does not seem to help.
My Code:
private val sendAndReceive = customSendAndReceive.getOrElse(HttpClientUtils.singleRequest)
.
.
.
def getActiveCampaigns: GetActiveCampaigns = () => {
val request = HttpRequest(
uri = s"$endpoint/admin/campaigns?status=PUBLISHED", // includes both PUBLISHED_READY and PUBLISHED_PAUSED
method = HttpMethods.GET,
headers = heathers
)
sendAndReceive(request).timed(getActiveCampaignsTimer).flatMap {
case HttpResponse(StatusCodes.OK, _, entity, _) =>
Unmarshal(entity).to[List[CampaignListDetailsDto]]
case response#HttpResponse(_, _, _, _) =>
response.discardEntityBytes()
Future.failed(new RuntimeException(s"Ad manager service exception: $response"))
case response =>
log.error(s"Error calling ad manager service: $response")
response.discardEntityBytes()
Future.failed(new RuntimeException(s"Ad manager service exception: $response"))
}
}
.
.
.
def getCampaignSpendData(getActiveCampaigns: GetActiveCampaigns, getCampaignTotalSpend: GetCampaignTotalSpend)(implicit ec: ExecutionContext): GetCampaignsSpendData = () => {
getActiveCampaigns()
.andThen {
case Failure(t) => log.error("Failed to fetch ads from ad manager", t)
}
.flatMap {
campaignList => Future.sequence(campaignList.map(campaign => budgetSpendPercentage(getCampaignTotalSpend)(campaign)))
}
}
Questions
What does this error exactly mean? Is it that it is able to connect to the endpoint but not able to get the complete data from it before the connection is closed/reset?
How can we address this issue?