CODEWITHSUNDEEP
prometheusgrafanapromql
FlamingBee
FlamingBee

Reputation: 145

Getting a count of distinct label values in prometheus/grafana

I am trying to create a table/chart in Grafana showing the total number of unique users who have logged in to a given application over a given time range (e.g. last 24 hours). I have a metric, app_request_path which records the number of requests hitting a specific path per minute:

app_request_count{app="my-app", path="/login"}

This gives me the following:

    app_request_count{app="my-app",path="/login",status="200",username="username1"}
    app_request_count{app="my-app",path="/login",status="200",username="username2"}

Now I want to count the number of unique usernames, so I run:

count_values("username", app_request_count{app="my_app", path="/login"})

and I get:

    {username="0"}
    {username="1"}
    {username="2"}
    {username="3"}
    {username="4"}
    {username="5"}

What am I missing / what am I doing wrong? Ideally I'd like to get a single scalar value that display the total number of unique usernames who have logged in in the past 24 hours.

Many thanks.

Upvotes: 10

Views: 23519

Answers (2)

valyala
valyala

Reputation: 17830

The following query should return the number of unique username label values encountered during the last 24 hours for the given labels app="my-app" and path="/login":

count(
  group(
    last_over_time(app_request_count{app="my-app", path="/login"}[24h])
  ) by (username)
)

How it works:

  1. The inner last_over_time(...[24h]) query makes sure that every unique time series is selected for the last 24 hours, even if this time series stopped receiving new samples during the last 24 hours. See last_over_time() docs.

  2. The group(...) by (username) returns a single time series per each unique username label. See group() docs.

  3. The count(...) returns the total number of time series returned from group(). This number matches the number of unique values for username label. See count() docs.

Upvotes: 3

brian-brazil
brian-brazil

Reputation: 34122

count without (username)(app_request_count)

count_values is for metric values, count is for time series. It's also not advised to have something like usernames as label values as they tend to be high cardinality. They may also be PII, which could have legal implications.

Upvotes: 12

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