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Summary quantiles respond +Inf if rps decreases to zero #303

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DifferentialOrange opened this issue Sep 16, 2021 · 3 comments · Fixed by #305
Closed

Summary quantiles respond +Inf if rps decreases to zero #303

DifferentialOrange opened this issue Sep 16, 2021 · 3 comments · Fixed by #305
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@DifferentialOrange
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If there are 0 new requests for some time, summary collector quantiles respond with +Inf values.

image

http_server_request_latency{path="/hello",method="GET",alias="tnt_router",status="200",quantile="0.5"} +Inf
http_server_request_latency{path="/hello",method="GET",alias="tnt_router",status="200",quantile="0.9"} +Inf
http_server_request_latency{path="/hello",method="GET",alias="tnt_router",status="200",quantile="0.99"} +Inf
http_server_request_latency{path="/goodbye",method="POST",alias="tnt_router",status="500",quantile="0.5"} +Inf
http_server_request_latency{path="/goodbye",method="POST",alias="tnt_router",status="500",quantile="0.9"} +Inf
http_server_request_latency{path="/goodbye",method="POST",alias="tnt_router",status="500",quantile="0.99"} +Inf
http_server_request_latency{path="/hell0",method="GET",alias="tnt_router",status="400",quantile="0.5"} +Inf
http_server_request_latency{path="/hell0",method="GET",alias="tnt_router",status="400",quantile="0.9"} +Inf
http_server_request_latency{path="/hell0",method="GET",alias="tnt_router",status="400",quantile="0.99"} +Inf

It breaks visualization with ugly vertical lines. I'm sure there are better approaches to handle this.

Reproducer

You may use https://github.com/tarantool/grafana-dashboard docker cluster and stop load container after several minutes.

docker-compose up
# let it generate some metrics
docker stop grafana-dashboard_load_generator_1
@yngvar-antonsson
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Now it's a part of the quantile algorithm and covers with tests:

metrics/test/quantile_test.lua

Line 144 in 7652824

g.test_query_on_empty_quantile = function()

We could convert values from empty quantile collector to null.

@DifferentialOrange
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Now it's a part of the quantile algorithm and covers with tests:

metrics/test/quantile_test.lua

Line 144 in 7652824

g.test_query_on_empty_quantile = function()

We could convert values from empty quantile collector to null.

I think it is a good idea

@yngvar-antonsson
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yngvar-antonsson commented Sep 16, 2021 •
edited

metrics/metrics/quantile.lua

Line 158 in 7652824

function stream:query(q) 

if s.n == 0 then
  return nil
end

Since stream:query function is called after buffer flush, if stream is empty (== 0) then there was no insertion in collector.

@DifferentialOrange

@DifferentialOrange DifferentialOrange self-assigned this Sep 17, 2021
DifferentialOrange added a commit that referenced this issue Sep 17, 2021
@DifferentialOrange
Set quantile value to nil if there are no samples provided for an age
9883725 
Closes #303
@DifferentialOrange DifferentialOrange mentioned this issue Sep 17, 2021
Merged
4 tasks
DifferentialOrange added a commit that referenced this issue Sep 17, 2021
@DifferentialOrange
Set quantile value to nil if there are no samples provided for an age
4b04408 
Closes #303
DifferentialOrange added a commit that referenced this issue Sep 21, 2021
@DifferentialOrange
Set quantile value to NAN if there are no samples provided for an age
23d8391 
Closes #303
DifferentialOrange added a commit to tarantool/crud that referenced this issue May 18, 2022
@DifferentialOrange
stats: separate quantile and average fields
ebc730a 
Add separate quantile (`latency_quantile_recent`) and average (
`latency_average`) fields to `crud.stats()` output. `latency` field and
tarantool/metrics output remains unchanged.

Before this patch, `latency` displayed `latency_quantile_recent` or
`latency_average` and there wasn't any was to see pre-computed average
if quantiles are enabled. But it may be useful if quantile is `nan`.

Quantiles may display `-nan` if there were no observations for a several
ages. Such behavior is expected [1] and valid: for example, Grafana
should ignore such values and they will be displayed as `No data` for
a window when there wasn't any requests.

1. tarantool/metrics#303

Closes #286
DifferentialOrange added a commit to tarantool/crud that referenced this issue May 18, 2022
@DifferentialOrange
stats: separate quantile and average fields
8fe6dbb 
Add separate quantile (`latency_quantile_recent`) and average (
`latency_average`) fields to `crud.stats()` output. `latency` field and
tarantool/metrics output remains unchanged.

Before this patch, `latency` displayed `latency_quantile_recent` or
`latency_average` and there wasn't any was to see pre-computed average
if quantiles are enabled. But it may be useful if quantile is `nan`.

Quantiles may display `-nan` if there were no observations for a several
ages. Such behavior is expected [1] and valid: for example, Grafana
should ignore such values and they will be displayed as `No data` for
a window when there wasn't any requests.

1. tarantool/metrics#303

Closes #286
DifferentialOrange added a commit to tarantool/crud that referenced this issue May 18, 2022
@DifferentialOrange
stats: separate quantile and average fields
4429a00 
Add separate quantile (`latency_quantile_recent`) and average (
`latency_average`) fields to `crud.stats()` output. `latency` field and
tarantool/metrics output remains unchanged.

Before this patch, `latency` displayed `latency_quantile_recent` or
`latency_average` and there wasn't any was to see pre-computed average
if quantiles are enabled. But it may be useful if quantile is `nan`.

Quantiles may display `-nan` if there were no observations for a several
ages. Such behavior is expected [1] and valid: for example, Grafana
should ignore such values and they will be displayed as `No data` for
a window when there wasn't any requests.

1. tarantool/metrics#303

Closes #286
DifferentialOrange added a commit to tarantool/crud that referenced this issue May 18, 2022
@DifferentialOrange
stats: separate quantile and average fields
2e5113d 
Add separate quantile (`latency_quantile_recent`) and average (
`latency_average`) fields to `crud.stats()` output. `latency` field and
tarantool/metrics output remains unchanged.

Before this patch, `latency` displayed `latency_quantile_recent` or
`latency_average` and there wasn't any was to see pre-computed average
if quantiles are enabled. But it may be useful if quantile is `nan`.

Quantiles may display `-nan` if there were no observations for a several
ages. Such behavior is expected [1] and valid: for example, Grafana
should ignore such values and they will be displayed as `No data` for
a window when there wasn't any requests.

1. tarantool/metrics#303

Closes #286
@DifferentialOrange DifferentialOrange mentioned this issue May 18, 2022
Merged
3 tasks
DifferentialOrange added a commit to tarantool/crud that referenced this issue May 18, 2022
@DifferentialOrange
stats: separate quantile and average fields
85e6ac8 
Add separate quantile (`latency_quantile_recent`) and average (
`latency_average`) fields to `crud.stats()` output. `latency` field and
tarantool/metrics output remains unchanged.

Before this patch, `latency` displayed `latency_quantile_recent` or
`latency_average` and there wasn't any was to see pre-computed average
if quantiles are enabled. But it may be useful if quantile is `nan`.

Quantiles may display `-nan` if there were no observations for a several
ages. Such behavior is expected [1] and valid: for example, Grafana
should ignore such values and they will be displayed as `No data` for
a window when there wasn't any requests.

1. tarantool/metrics#303

Closes #286
DifferentialOrange added a commit to tarantool/crud that referenced this issue May 19, 2022
@DifferentialOrange
stats: separate quantile and average fields
95e6c30 
Add separate quantile (`latency_quantile_recent`) and average (
`latency_average`) fields to `crud.stats()` output. `latency` field and
tarantool/metrics output remains unchanged.

Before this patch, `latency` displayed `latency_quantile_recent` or
`latency_average` and there wasn't any was to see pre-computed average
if quantiles are enabled. But it may be useful if quantile is `nan`.

Quantiles may display `-nan` if there were no observations for a several
ages. Such behavior is expected [1] and valid: for example, Grafana
should ignore such values and they will be displayed as `No data` for
a window when there wasn't any requests.

1. tarantool/metrics#303

Closes #286
DifferentialOrange added a commit to tarantool/crud that referenced this issue May 20, 2022
@DifferentialOrange
stats: separate quantile and average fields
35ac849 
Add separate quantile (`latency_quantile_recent`) and average (
`latency_average`) fields to `crud.stats()` output. `latency` field and
tarantool/metrics output remains unchanged.

Before this patch, `latency` displayed `latency_quantile_recent` or
`latency_average` and there wasn't any was to see pre-computed average
if quantiles are enabled. But it may be useful if quantile is `nan`.

Quantiles may display `-nan` if there were no observations for a several
ages. Such behavior is expected [1] and valid: for example, Grafana
should ignore such values and they will be displayed as `No data` for
a window when there wasn't any requests.

1. tarantool/metrics#303

Closes #286
DifferentialOrange added a commit to tarantool/crud that referenced this issue May 20, 2022
@DifferentialOrange
stats: separate quantile and average fields
4a76d92 
Add separate quantile (`latency_quantile_recent`) and average (
`latency_average`) fields to `crud.stats()` output. `latency` field and
tarantool/metrics output remains unchanged.

Before this patch, `latency` displayed `latency_quantile_recent` or
`latency_average` and there wasn't any was to see pre-computed average
if quantiles are enabled. But it may be useful if quantile is `nan`.

Quantiles may display `-nan` if there were no observations for a several
ages. Such behavior is expected [1] and valid: for example, Grafana
should ignore such values and they will be displayed as `No data` for
a window when there wasn't any requests.

1. tarantool/metrics#303

Closes #286
DifferentialOrange added a commit to tarantool/crud that referenced this issue May 20, 2022
@DifferentialOrange
stats: separate quantile and average fields
c66d330 
Add separate quantile (`latency_quantile_recent`) and average (
`latency_average`) fields to `crud.stats()` output. `latency` field and
tarantool/metrics output remains unchanged.

Before this patch, `latency` displayed `latency_quantile_recent` or
`latency_average` and there wasn't any was to see pre-computed average
if quantiles are enabled. But it may be useful if quantile is `nan`.

Quantiles may display `-nan` if there were no observations for a several
ages. Such behavior is expected [1] and valid: for example, Grafana
should ignore such values and they will be displayed as `No data` for
a window when there wasn't any requests.

1. tarantool/metrics#303

Closes #286
Totktonada pushed a commit to tarantool/crud that referenced this issue May 20, 2022
@DifferentialOrange @Totktonada
stats: separate quantile and average fields
e709a87 
Add separate quantile (`latency_quantile_recent`) and average (
`latency_average`) fields to `crud.stats()` output. `latency` field and
tarantool/metrics output remains unchanged.

Before this patch, `latency` displayed `latency_quantile_recent` or
`latency_average` and there wasn't any was to see pre-computed average
if quantiles are enabled. But it may be useful if quantile is `nan`.

Quantiles may display `-nan` if there were no observations for a several
ages. Such behavior is expected [1] and valid: for example, Grafana
should ignore such values and they will be displayed as `No data` for
a window when there wasn't any requests.

1. tarantool/metrics#303

Closes #286
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Set quantile value to NAN if there are no samples provided for an age tarantool/metrics
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@DifferentialOrange @yngvar-antonsson