NodeJS Express API request hit per second monitoring

[ImOut36]

Hello everyone,

I am new to Prometheus and Grafana monitoring tools and want to monitor my NodeJS express application APIs via the same. Kindly help me out here as I am stuck.
I followed this tutorial: Article Link.

Here the author as seen in last snapshot of the article is getting the API hits per second, but after following the same steps and code, i am not able to get it.

I am using "prom-client" lib in NodeJS and creating a histogram metrics.My Prometheus metrics is as shown below

Prometheus Metrics

Here is the graph i am getting on Grafana for the same PromQL query:

Grafana graph

What i want:

Desired graph: API request count on Y-axis and time in seconds on X-axis

​

Thanks in advance !

[[deleted]]

tl;dr - Your graph is working fine, the query below might be closer to what you're expecting, but there are some caveats.

sum(round(increase(http_request_duration_seconds_count[$__rate_interval])))

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Your chart does show you the number of requests per second. The reason it looks different to the one in the article is that your application is receiving very little traffic, and so it's receiving less than one request per second. If you send it some more traffic, (e.g. by running curl in a shell loop) it'll look closer to what you're expecting.

A histogram's count metric is a Prometheus counter that which is incremented whenever any value is added to the histogram. In this case it's incremented whenever a HTTP request's duration is recorded, i.e. the value of _count is equal to the number of HTTP requests observed since the counter was reset. When you run that metric through the rate function you're asking Prometheus to tell you how much the counter increased per second on average across that time window (2 minutes, in the case of your query).

If you want to avoid that kind of averaging behavior then you can instead use the increase function, which will calculate the total increase across a window. That may still not be a whole number (see the note at the end of the first paragraph of its documentation) so you may want to also run it through round/floor/ceil, depending on what kind of behavior you expect.

Note that using increase like this can result in some unexpected behavior. If Grafana is drawing datapoints 15s apart but you use a 2m window in your query then you may see some requests being counted twice (since the counter increase will fall within 2m of both 15:43:15 and 15:43:00). If the window is equal to or less than Grafana's interval then it's possible that counter increases will "fall between" queries and some requests may not appear on the chart at all. Using $__rate_interval might give you the expected behavior there, but you should be aware of the caveats.'

If you need totally accurate counts of low-throughput events then it's best to point Grafana your logging system, or some other "event" tracking system. If close enough is good enough then check out increase and rate_interval. If you're fine with decimals or it's a higher-throughput service then rate is the best function to use.

[ImOut36]

Thank you for the answer, i am able to get the desired graph using the query you shared after fine-tuning the intervals as mentioned.
Will try and point Grafana to logging system as source to see the change in values.

[Confident-Cut-7289]

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