topic Re: Client-Side Response Time in Real User Monitoring

Client-Side Response Time

alekz_silva — Mon, 19 Jan 2026 07:47:05 GMT

Hello,
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.

Re: HELP - Client-Side Response Time

AntonioSousa — Fri, 19 Nov 2021 14:22:50 GMT

@alekz_silva,

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.

Re: Client-Side Response Time

Julius_Loman — Mon, 22 Nov 2021 07:34:18 GMT

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.

Re: Client-Side Response Time

alekz_silva — Mon, 22 Nov 2021 13:42:23 GMT

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.

Re: Client-Side Response Time

AntonioSousa — Mon, 22 Nov 2021 19:10:42 GMT

@alekz_silva

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.)

Re: Client-Side Response Time

alekz_silva — Mon, 22 Nov 2021 20:22:26 GMT

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.

Re: Client-Side Response Time

AntonioSousa — Mon, 22 Nov 2021 21:07:09 GMT

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?

Re: Client-Side Response Time

julien_duhamel1 — Sun, 05 Dec 2021 06:06:00 GMT

in this case, my first move, is try to evaluate the argments. Your descrption seems finger point calls (front->Back). In 90% the issue come from code execution. Sometimes related to a "batch" who use ressources. If i cannot had access to code lvl, a comparaison with users session's waterfall may a good start point.( Compare ressource load by type of browser/Timesries/ressources/XRH or Load ?) etc etc

Re: Client-Side Response Time

alekz_silva — Wed, 15 Dec 2021 09:46:18 GMT

Thanks again for your willingness to help. Calls are made from servers in the AWS cloud. I will attach images from today's request.

Re: Client-Side Response Time

AntonioSousa — Wed, 15 Dec 2021 09:48:26 GMT

@alekz_silva

As a matter of caution, I have removed the attachment that you put here, not only because it is classified as confidential, but also because it really may contain sensitive information. I'm in the process of analyzing the information you provided, and will be back in a few minutes.

Re: Client-Side Response Time

AntonioSousa — Wed, 15 Dec 2021 11:30:07 GMT

@alekz_silva

I have annotated the Purepath below. It does seem that times are quite high when invoking those services. They even continue working, despite the original client request being timed out at 1 minute.

For what I have seen you should concentrate your efforts on possibly two explanations for this:

The .Net service that is taking too much time to be invoked. There might be thread issues or other related factors that stall invocation. Take a look at Method Hotspots here, and if you have it activated, at IIS Modules in the "Response time hotspots" of that service.
Since you mention the AWS cloud, I'm not sure if these invocations are all inside the cloud, or if they invoke on-prem servers. If the latter is the case, please check network latencies, traffic & retransmissions. The values are very high, so I believe that should not be the case, but please check it out.

Re: Client-Side Response Time

akankshabarge — Thu, 15 Jan 2026 16:15:40 GMT

We are facing the same issue. The request originates from DataPower (NGINX) and gets terminated after 25 seconds due to a request timeout. After that, the request reaches the application web server, which is behind an NGINX load balancer, and this returns a 200 OK response after 31.7 seconds.

When this request appears in the ASP.NET request span, the timeline shows a light blue bar at the start, which seems to represent client-side response time. This light blue bar lasts for approximately 31.5 seconds. After this bar ends, the actual code execution begins and takes only a few milliseconds. The related MSSQL queries also complete within a few milliseconds.

At this point, we have not been able to identify why this light blue bar shows such a high response time, which accounts for almost the entire request duration. Please help us investigate this issue

Re: Client-Side Response Time

Julius_Loman — Thu, 15 Jan 2026 21:22:37 GMT

The client response time (light blue) is the time between when the calling service starts the request and called service starts to process the request. Can be network congestion, queued request, garbage collection happening, ...

Re: Client-Side Response Time

mehakpuri01 — Thu, 05 Feb 2026 08:23:59 GMT

Hi All,

We are too experiencing the same issue in our environment wherein the server response time is 102ms and client side response time is 7s which leads to socket hang up exceptions in upstream services, however for an ECS based application with the API being hosted on ECS i mean, what metrics would we check in this case?

Thanks!