Overview

This documentation provides a detailed guide on configuring the Thanos development environment. Focused on expert developers, this guide will delve into various configuration options relevant to a development setting.

Configuration Options

Global Configuration

Thanos allows specifying various configurations for its components through command line flags and configuration files. This section discusses some of the key settings and their usage in a development environment.

Command-Line Flags

Thanos components can be configured using command-line flags. Below are some important flags that control various aspects of the configuration:

1. Reloader Configuration The reloader in Thanos watches for changes in the configuration file and automatically applies them. Here’s how to set up its configuration:

   func (rc *reloaderConfig) registerFlag(cmd extkingpin.FlagClause) *reloaderConfig {
       cmd.Flag("reloader.config-file",
           "Config file watched by the reloader.").
           Default("").StringVar(&rc.confFile)
       cmd.Flag("reloader.config-envsubst-file",
           "Output file for environment variable substituted config file.").
           Default("").StringVar(&rc.envVarConfFile)
       cmd.Flag("reloader.rule-dir",
           "Rule directories for the reloader to refresh (repeated field).").
           StringsVar(&rc.ruleDirectories)
       cmd.Flag("reloader.watch-interval",
           "Controls how often reloader re-reads config and rules.").
           Default("3m").DurationVar(&rc.watchInterval)
       cmd.Flag("reloader.retry-interval",
           "Controls how often reloader retries config reload in case of error.").
           Default("5s").DurationVar(&rc.retryInterval)
       cmd.Flag("reloader.method",
           "Method used to reload the configuration.").
           Default(HTTPReloadMethod).EnumVar(&rc.method, HTTPReloadMethod, SignalReloadMethod)
       cmd.Flag("reloader.process-name",
           "Executable name used to match the process being reloaded when using the signal method.").
           Default("prometheus").StringVar(&rc.processName)
   
       return rc
   }
   

2. Tracing Configuration Thanos supports multiple tracing backends that adhere to the opentracing.Tracer interface. Configuration can be specified through a YAML file or inline:

   // Example in YAML file
   --tracing.config-file=<path_to_yaml_file>
   

   Alternatively, you may specify it directly with:

   --tracing.config=<yaml_config>
   

   For detailed configuration formats, refer to the Thanos tracing documentation.

3. Prometheus Configuration Thanos retains the Prometheus-compatible configuration structure. Here’s how to leverage it:

   # Example prometheus configuration
   global:
     scrape_interval: 15s
   scrape_configs:
     - job_name: 'example'
       static_configs:
         - targets: ['localhost:9090']
   

Environment Variables

In a development environment, it’s common to use environment variables for configuration. Thanos supports environment variable substitution in configuration files:

func expandEnv(b []byte) (r []byte, err error) {
    r = envRe.ReplaceAllFunc(b, func(n []byte) []byte {
        if err != nil {
            return nil
        }
        n = n[2 : len(n)-1]
        v, ok := os.LookupEnv(string(n))
        if !ok {
            err = errors.Errorf("found reference to unset environment variable %q", n)
            return nil
        }
        return []byte(v)
    })
    return r, err
}

Configuration File Structure

Thanos can utilize configuration files in formats such as JSON and YAML. Regardless of the format, the structure should conform to the expected layout for the Thanos components being configured.

For instance, a simple YAML configuration for a storage component may look like:

type: S3
config:
  bucket: my-bucket
  endpoint: s3.amazonaws.com
  access_key: ${ACCESS_KEY}
  secret_key: ${SECRET_KEY}

Testing Configuration

During the development of Thanos, testing configurations are pivotal. Be aware of the build constraints when running tests:

• Exclude linux and stringlabels based constraints defined in the files when tetsing:

go test -tags='!linux,!stringlabels'

Conclusion

Configuring Thanos in a development environment entails a careful setup of command-line flags, environment variables, and configuration files. Developers can leverage the above guidelines and examples to tailor their Thanos instance to meet specific needs within a development context.

For further details, refer to the Thanos documentation, particularly around configuration formats and components.

Source: Thanos Codebase and Documentation