From 1e6c93250172946eeb38e94a92a1fd12c9d3011e Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 7 Nov 2018 13:22:44 +0100 Subject: Merging upstream version 1.11.0+dfsg. Signed-off-by: Daniel Baumann --- web/api/queries/ses/README.md | 54 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 web/api/queries/ses/README.md (limited to 'web/api/queries/ses/README.md') diff --git a/web/api/queries/ses/README.md b/web/api/queries/ses/README.md new file mode 100644 index 000000000..b5dacea83 --- /dev/null +++ b/web/api/queries/ses/README.md @@ -0,0 +1,54 @@ +# Single (or Simple) Exponential Smoothing (`ses`) + +> This query is also available as `ema` and `ewma`. + +An exponential moving average (`ema`), also known as an exponentially weighted moving average (`ewma`) +is a first-order infinite impulse response filter that applies weighting factors which decrease +exponentially. The weighting for each older datum decreases exponentially, never reaching zero. + +In simple terms, this is like an average value, but more recent values are given more weight. + +Netdata automatically adjusts the weight (`alpha`) based on the number of values processed, +using the formula: + +``` +window = max(number of values, 15) +alpha = 2 / (window + 1) +``` + +You can change the fixed value `15` by setting in `netdata.conf`: + +``` +[web] + ses max window = 15 +``` + +## how to use + +Use it in alarms like this: + +``` + alarm: my_alarm + on: my_chart +lookup: ses -1m unaligned of my_dimension + warn: $this > 1000 +``` + +`ses` does not change the units. For example, if the chart units is `requests/sec`, the exponential +moving average will be again expressed in the same units. + +It can also be used in APIs and badges as `&group=ses` in the URL. + +## Examples + +Examining last 1 minute `successful` web server responses: + +- ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=min&after=-60&label=min) +- ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=average&after=-60&label=average&value_color=yellow) +- ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=ses&after=-60&label=single+exponential+smoothing&value_color=orange) +- ![](https://registry.my-netdata.io/api/v1/badge.svg?chart=web_log_nginx.response_statuses&options=unaligned&dimensions=success&group=max&after=-60&label=max) + +## References + +- [https://en.wikipedia.org/wiki/Moving_average#exponential-moving-average](https://en.wikipedia.org/wiki/Moving_average#exponential-moving-average) +- [https://en.wikipedia.org/wiki/Exponential_smoothing](https://en.wikipedia.org/wiki/Exponential_smoothing). -- cgit v1.2.3