I have a .NetCore C# project which performs an HTTP POST. The project is set up in Kubernetes and I've noticed the logs below:

Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:45 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:46 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:47 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:48 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:49 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:50 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:51 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:52 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:53 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:54 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:55 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:43:56 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:44:33 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:44:34 +00:00".
warn: Microsoft.AspNetCore.Server.Kestrel[22]
      Heartbeat took longer than "00:00:01" at "02/22/2020 15:44:35 +00:00".

After some initial research, it seems this is a common result of threadpool starvation. Accordingly, in November last year, I made the post asynchronous and also logged the Max threads and Available threads as follows for monitoring purposes:

ThreadPool.GetMaxThreads(out int workerThreads, out int completionPortThreads);
ThreadPool.GetAvailableThreads(out int workerThreadAvailable, out int completionPortThreadsAvailable);
_log.Info(new { message = $"Max threads = {workerThreads} and Available threads = {workerThreadAvailable}" });

Consistently over the past few months, the logging shows: Max threads = 32767 and Available threads = 32766. That seems fine, however, I'm noticing the same Heartbeat error so am wondering if this really is a threadpool starvation issue. Might someone know what else is going on and if this error is actually a result of something else? Any investigation/resolution tips for this would be much appreciated!