How to resolve Heartbeat took longer than "00:00:01" failure? - multithreading

Question

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!

Answer 1

This is a resource issue, as #andy pointed out in his response.
According to OP, the solution to this problem is to either increase the server's CPU capacity (vertically) or the number of instances of your app (horizontally).