Pie Charts

Introduction

Pie charts are circular statistical graphics divided into slices to illustrate numerical proportions. In Grafana, pie charts provide an effective way to show the relative sizes of data points as parts of a whole. They're particularly useful when you want to emphasize a significant proportion or compare a limited number of categories.

This guide will walk you through creating and customizing pie charts in Grafana, explaining best practices for their effective use, and showing practical applications with real-world examples.

When to Use Pie Charts

Pie charts are most effective when:

• You need to show parts of a whole (proportional data)
• You have a relatively small number of categories (ideally 2-7)
• The differences between values are significant enough to be visually distinguishable
• You want to emphasize a particular segment or proportion

They are less effective when:

• You have many categories (becomes cluttered)
• Categories have similar values (difficult to compare visually)
• You need to show precise values or changes over time

Creating a Basic Pie Chart in Grafana

Let's start by creating a simple pie chart in Grafana:

Step 1: Set Up the Panel

1. Create a new dashboard or edit an existing one
2. Add a new panel
3. In the visualization options, select "Pie Chart"

Dashboard -> Add panel -> Visualizations -> Pie Chart

Step 2: Configure the Data Query

For our example, we'll use a simple query that returns categorical data:

sql

SELECT category, COUNT(*) as count 
FROM events 
GROUP BY category
ORDER BY count DESC

This query counts events by category, which is perfect for a pie chart visualization.

Step 3: Basic Pie Chart Configuration

In the panel options:

1. Navigate to the "Panel Options" tab
2. Set a descriptive title like "Events by Category"
3. Under the "Pie Chart" section, configure:
   • Values: Select your metric (count in our example)
   • Labels: Choose whether to show labels inside or outside the slices
   • Legend: Configure to show or hide the legend

Your basic pie chart is now ready to display!

Advanced Customization

Grafana offers several customization options to enhance your pie charts:

Chart Type Options

Grafana provides three main types of circular charts:

1. Pie Chart: The traditional circular chart divided into slices
2. Donut Chart: A pie chart with a hole in the center
3. Gauge: Shows a single value against a scale (useful for showing progress toward a goal)

To switch between these:

Panel Options -> Pie Chart -> Type -> Select (Pie/Donut/Gauge)

Label Configuration

You can customize how labels appear on your chart:

Panel Options -> Pie Chart -> Labels -> Position (Inside/Outside/Auto)

For label content, you can show:

• Name
• Percentage
• Value

Color Schemes

Customize colors to make your pie chart more meaningful:

Panel Options -> Standard options -> Color scheme

Grafana provides several color palettes, including:

• Classic
• Green-Yellow-Red
• Blue-Yellow-Red
• Custom schemes

Tooltip Customization

Configure what appears when users hover over chart segments:

Panel Options -> Tooltip -> Mode (Single/All/Hidden)

Best Practices for Pie Charts

To create effective pie charts in Grafana:

1. Limit the number of slices: Use 7 or fewer categories for readability
2. Order segments logically: Place the largest slice at 12 o'clock position and proceed clockwise
3. Consider aggregating small values: Combine small values into an "Other" category if they're less than 5% of the total
4. Use clear labels: Ensure labels are readable and descriptive
5. Choose appropriate colors: Use distinct colors that provide adequate contrast
6. Add context with legends: Include legends to provide more information about each category

Practical Examples

Let's look at some real-world applications of pie charts in Grafana:

Example 1: Server Resource Allocation

Create a pie chart showing how disk space is allocated across different services:

sql

SELECT 
  service_name,
  SUM(allocated_gb) as space
FROM storage_allocation
GROUP BY service_name

This visualization helps identify which services are consuming the most resources.

Example 2: Error Distribution by Type

Monitor the distribution of error types in your application:

sql

SELECT 
  error_type,
  COUNT(*) as count
FROM error_logs
WHERE timestamp > NOW() - INTERVAL 24 HOUR
GROUP BY error_type

This helps quickly identify which types of errors are most frequent.

Example 3: Traffic Sources

Analyze where your website traffic is coming from:

sql

SELECT 
  referrer_source,
  COUNT(distinct session_id) as visits
FROM user_sessions
WHERE date = CURRENT_DATE
GROUP BY referrer_source

Alternatives to Consider

Sometimes pie charts aren't the best choice. Consider these alternatives:

1. Bar Charts: Better for comparing exact values or showing many categories
2. Gauge: Better for showing progress toward a single goal
3. Time Series: Better for showing changes over time
4. Stat Panel: Better for displaying a single important metric

Advanced Technique: Using Pie Charts in Dashboards

Pie charts work well as part of larger dashboards. Here are some integration tips:

1. Dashboard Variables: Create template variables to filter your pie chart data along with other panels
2. Dashboard Links: Link your pie chart to detailed panels for drill-down analysis
3. Panel Links: Add links to external resources or detailed views

Example dashboard variable setup:

Dashboard Settings -> Variables -> Add variable
Name: service
Query: SELECT distinct service_name FROM services

Then modify your pie chart query to use this variable:

sql

SELECT 
  category,
  COUNT(*) as count 
FROM events 
WHERE service = '$service'
GROUP BY category

Troubleshooting Common Issues

If your pie chart isn't displaying correctly:

1. No data appears: Check that your query returns data in the expected format
2. Too many slices: Consider using a filter or aggregating smaller values
3. Labels overlapping: Try changing label position or reducing the text size
4. Misleading proportions: Ensure your query is calculating proportions correctly

Summary

Pie charts in Grafana are powerful tools for visualizing proportional data when used appropriately. Key takeaways:

• Use pie charts to show parts of a whole with a limited number of categories
• Customize colors, labels, and tooltips to enhance readability
• Follow best practices like limiting slices and using clear labels
• Consider alternatives when pie charts aren't the best choice
• Integrate pie charts into dashboards with variables for interactive analysis

Exercises

1. Create a pie chart showing CPU usage across different applications
2. Modify a pie chart to display as a donut chart with custom colors
3. Create a dashboard with a pie chart that responds to template variables
4. Build a pie chart that shows the top 5 categories and groups all others into an "Other" category

Additional Resources

• Grafana Documentation on Pie Charts
• Data Visualization Best Practices
• Dashboard Variables in Grafana