Plot

Generate data file for GNU Plot

The Plot output plugin generates data files in a format compatible with GNU Plot (gnuplot), a command-line graphing tool. This plugin lets you export your telemetry data for visualization and analysis using gnuplot.

Configuration parameters

This plugin supports the following parameters:

Key	Description	Default
File	Set filename to store the records. If not set, the filename will be the tag associated with the records. If the file can't be opened, the plugin falls back to writing to STDOUT.	none
Key	Specify the key name from the record to extract as the value. The value must be a numeric type (integer or float). If not specified, the plugin uses the first field from the record.	none

Output format

The Plot output plugin generates data files in a format suitable for gnuplot. The output format is space-separated values with two columns: timestamp and value.

The output format is:

timestamp value

Where:

• timestamp is a floating-point Unix timestamp

• value is the numeric value extracted from the specified key (or the first field if Key isn't specified)

The plugin only supports numeric values (integers or floats). If the specified key isn't found or the value isn't numeric, an error is logged and the record is skipped.

Get started

You can run the plugin from the command line or through the configuration file.

Command line

From the command line you can generate plot data files with the following options:

fluent-bit -i cpu -o plot -p file=cpu_data.dat -p key=cpu_p

This example extracts the cpu_p field from CPU metrics and writes timestamp-value pairs to cpu_data.dat.

Configuration file

In your main configuration file append the following:

fluent-bit.yaml

pipeline:
  inputs:
    - name: cpu
      tag: cpu

  outputs:
    - name: plot
      match: '*'
      file: cpu_data.dat
      key: cpu_p

fluent-bit.conf

Example usage with gnuplot

After generating the data file with Fluent Bit, you can use gnuplot to visualize the data:

1. Generate the data file:

fluent-bit -i cpu -o plot -p file=cpu_data.dat -p key=cpu_p -f 1

This command collects CPU metrics, extracts the cpu_p field (CPU percentage), and writes timestamp-value pairs to cpu_data.dat. The output file will contain lines like:

1704067200.123456 25.5
1704067201.123456 30.2
1704067202.123456 28.7

1. Create a gnuplot script (for example, plot.gp):

set terminal png
set output "cpu_usage.png"
set xlabel "Time"
set ylabel "CPU Usage (%)"
set xdata time
set timefmt "%s"
set format x "%H:%M:%S"
plot "cpu_data.dat" using 1:2 with lines title "CPU Usage"

1. Run gnuplot:

gnuplot plot.gp

This will generate a PNG image file showing the CPU usage over time.

• The Key parameter is optional. If not specified, the plugin uses the first field from the record.

• Only numeric values (integers or floats) are supported. Non-numeric values will cause the record to be skipped with an error logged.

• If the specified Key isn't found in a record, an error is logged and that record is skipped.

• If the output file can't be opened (for example, due to permissions), the plugin automatically falls back to writing to STDOUT.

• The output file is opened in append mode, so new data is added to existing files.