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Client-Side Response Time


I'm monitoring the environment and I've noticed that several requests are getting a high response time in "Client-Side Response Time" or light blue bar in PurePath view.

The API runs on Windows servers and IIS.
I would like some help in identifying the possible causes so that only a few requests have this high processing time. Apparently, processing occurs but the API takes a long time to respond to the client, generating a timeout in every transaction.

DynaMight Leader
DynaMight Leader


This can happen for several reasons I quickly remember:

  • Network latency between server originating request and server receiving request. Since you mention that this is only happening in a few requests, this is most likely not the case.
  • Latency being introduced by some type of load balancing. This can lead to the client experiencing more delay than what is seen from the server side.
  • Eventual retransmissions occurring during the request
  • Resource shortage at the thread/socket level. Check these values on the services that are being invoked.
Antonio Sousa

DynaMight Guru
DynaMight Guru

Most likely as @AntonioSousa writes the shortage on socket/thread/pool - whatever is used to establish the communication.  Other reasons mentioned would have an effect on most of the requests.

I'd also suggest checking the Code-level tab in your PurePath (at the calling service node), maybe you can find some additional information there.

TEMPEST a.s., Slovakia, Dynatrace Master Partner

I compared two requests (one successfully and the other with the client-side with high response time) and identified that both perform exactly the same activities. In other words, the system processes the request but for some reason there is an excessive delay in the response to the client. In this case, could it still be something related to threads and pool? Unfortunately, at code-level there is no information regarding the light blue purepath bar.


Yes, all possibilities still apply. Your problems are certainly occurring before your code starts executing. You can eventually get more information by looking at the following points:

  • Response Time Hotspots and checking out if there are IIS modules with large percentage of code execution
  • Checking retransmissions at the host level, and if they are different hosts, on both the client & server side.
  • Check out issues with Connectivity at the process level

To understand the problem better, let us know if these requests happen always in the same host, or if they happen between distinct servers? If it's the latter case, as I suspect, please consider investigating what happen in between (load balancers, firewalls, etc.)

Antonio Sousa

APIS are distributed across 6 identical servers and traffic is controlled by the load balancer. The problem occurs on some transactions but on all servers.

So, I believe there are 6 servers that are receiving the calls you mentioned above.

Can you tell us a little bit more on who is making the requests. If you have client side timings, it means that you have servers that are being monitored also by OneAgent, and are making the calls. Can you tell us a little bit more about them?

Antonio Sousa