python.d changefinder icon

python.d changefinder

python.d changefinder

Plugin: python.d.plugin Module: changefinder


This collector uses the Python changefinder library to perform online changepoint detection on your Netdata charts and/or dimensions.

Instead of this collector just collecting data, it also does some computation on the data it collects to return a changepoint score for each chart or dimension you configure it to work on. This is an online machine learning algorithm so there is no batch step to train the model, instead it evolves over time as more data arrives. That makes this particular algorithm quite cheap to compute at each step of data collection (see the notes section below for more details) and it should scale fairly well to work on lots of charts or hosts (if running on a parent node for example).

Notes - It may take an hour or two (depending on your choice of n_score_samples) for the collector to ‘settle’ into it’s

typical behaviour in terms of the trained models and scores you will see in the normal running of your node. Mainly this is because it can take a while to build up a proper distribution of previous scores in over to convert the raw score returned by the ChangeFinder algorithm into a percentile based on the most recent n_score_samples that have already been produced. So when you first turn the collector on, it will have a lot of flags in the beginning and then should ‘settle down’ once it has built up enough history. This is a typical characteristic of online machine learning approaches which need some initial window of time before they can be useful.

  • As this collector does most of the work in Python itself, you may want to try it out first on a test or development system to get a sense of its performance characteristics on a node similar to where you would like to use it.
  • On a development n1-standard-2 (2 vCPUs, 7.5 GB memory) vm running Ubuntu 18.04 LTS and not doing any work some of the typical performance characteristics we saw from running this collector (with defaults) were:
    • A runtime (netdata.runtime_changefinder) of ~30ms.
    • Typically ~1% additional cpu usage.
    • About ~85mb of ram (apps.mem) being continually used by the python.d.plugin under default configuration.

This collector is supported on all platforms.

This collector supports collecting metrics from multiple instances of this integration, including remote instances.

Default Behavior


By default this collector will work over all system.* charts.


The default configuration for this integration does not impose any limits on data collection.

Performance Impact

The default configuration for this integration is not expected to impose a significant performance impact on the system.



Python Requirements

This collector will only work with Python 3 and requires the packages below be installed.

# become netdata user
sudo su -s /bin/bash netdata
# install required packages for the netdata user
pip3 install --user numpy==1.19.5 changefinder==0.03 scipy==1.5.4

Note: if you need to tell Netdata to use Python 3 then you can pass the below command in the python plugin section of your netdata.conf file.

[ plugin:python.d ]
  # update every = 1
  command options = -ppython3



The configuration file name for this integration is python.d/changefinder.conf.

You can edit the configuration file using the edit-config script from the Netdata config directory.

cd /etc/netdata 2>/dev/null || cd /opt/netdata/etc/netdata
sudo ./edit-config python.d/changefinder.conf


There are 2 sections:

  • Global variables
  • One or more JOBS that can define multiple different instances to monitor.

The following options can be defined globally: priority, penalty, autodetection_retry, update_every, but can also be defined per JOB to override the global values.

Additionally, the following collapsed table contains all the options that can be configured inside a JOB definition.

Every configuration JOB starts with a job_name value which will appear in the dashboard, unless a name parameter is specified.

Name Description Default Required
charts_regex what charts to pull data for - A regex like system\..*/ or system\..*/apps.cpu/apps.mem etc. system..* yes
charts_to_exclude charts to exclude, useful if you would like to exclude some specific charts. note: should be a ‘,’ separated string like ‘,’. no
mode get ChangeFinder scores ‘per_dim’ or ‘per_chart’. per_chart yes
cf_r default parameters that can be passed to the changefinder library. 0.5 no
cf_order default parameters that can be passed to the changefinder library. 1 no
cf_smooth default parameters that can be passed to the changefinder library. 15 no
cf_threshold the percentile above which scores will be flagged. 99 no
n_score_samples the number of recent scores to use when calculating the percentile of the changefinder score. 14400 no
show_scores set to true if you also want to chart the percentile scores in addition to the flags. (mainly useful for debugging or if you want to dive deeper on how the scores are evolving over time) no no



Default configuration.

  name: 'local'
  host: ''
  charts_regex: 'system\..*'
  charts_to_exclude: ''
  mode: 'per_chart'
  cf_r: 0.5
  cf_order: 1
  cf_smooth: 15
  cf_threshold: 99
  n_score_samples: 14400
  show_scores: false


Metrics grouped by scope.

The scope defines the instance that the metric belongs to. An instance is uniquely identified by a set of labels.

Per python.d changefinder instance

This scope has no labels.


Metric Dimensions Unit
changefinder.scores a dimension per chart score
changefinder.flags a dimension per chart flag


There are no alerts configured by default for this integration.


Debug Mode

To troubleshoot issues with the changefinder collector, run the python.d.plugin with the debug option enabled. The output should give you clues as to why the collector isn’t working.

  • Navigate to the plugins.d directory, usually at /usr/libexec/netdata/plugins.d/. If that’s not the case on your system, open netdata.conf and look for the plugins setting under [directories].

    cd /usr/libexec/netdata/plugins.d/
  • Switch to the netdata user.

    sudo -u netdata -s
  • Run the python.d.plugin to debug the collector:

    ./python.d.plugin changefinder debug trace

Getting Logs

If you’re encountering problems with the changefinder collector, follow these steps to retrieve logs and identify potential issues:

  • Run the command specific to your system (systemd, non-systemd, or Docker container).
  • Examine the output for any warnings or error messages that might indicate issues. These messages should provide clues about the root cause of the problem.

System with systemd

Use the following command to view logs generated since the last Netdata service restart:

journalctl _SYSTEMD_INVOCATION_ID="$(systemctl show --value --property=InvocationID netdata)" --namespace=netdata --grep changefinder

System without systemd

Locate the collector log file, typically at /var/log/netdata/collector.log, and use grep to filter for collector’s name:

grep changefinder /var/log/netdata/collector.log

Note: This method shows logs from all restarts. Focus on the latest entries for troubleshooting current issues.

Docker Container

If your Netdata runs in a Docker container named “netdata” (replace if different), use this command:

docker logs netdata 2>&1 | grep changefinder

Debug Mode

Log Messages

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