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create-runtime-setting

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Create a new RuntimeSetting that can be changed at runtime via `agent config set/get` and the config API

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Create a new RuntimeSetting implementation for the Datadog Agent. RuntimeSettings are settings that can be read and changed at runtime via:

  • The CLI: agent config get <setting>, agent config set <setting> <value>, agent config list-runtime
  • The HTTP API: GET /config/{setting}, POST /config/{setting}

Instructions

Step 1: Gather information from the user

Use AskUserQuestion to collect the following. If $ARGUMENTS provides the setting name, skip that question.

  1. Setting name (the config key, e.g. log_payloads, dogstatsd_stats): the name used to register and access the setting via the API.

  2. Value type: What type of value does this setting hold?

    • Boolean (true/false)
    • Integer
    • String
    • String slice (list of strings)

  3. Description: A human-readable description of what this setting controls (shown in /config/list-runtime).

  4. Hidden: Should this setting be hidden from the public runtime settings list? (default: false)

  5. Scope: Where should this setting live?

    • Shared (pkg/config/settings/) — Used by multiple agent services (agent, trace-agent, process-agent, etc.)
    • Agent-specific (cmd/agent/subcommands/run/internal/settings/) — Only used by the core agent

  6. Config key: The datadog.yaml config key this setting maps to (e.g. log_payloads, internal_profiling.enabled). Often the same as the setting name, but can differ.

  7. Which services should register it: Ask which services should have this setting registered:

    • Core Agent (cmd/agent/subcommands/run/command.go)
    • Cluster Agent (cmd/cluster-agent/subcommands/start/command.go)
    • Trace Agent (cmd/trace-agent/subcommands/run/command.go)
    • Process Agent (cmd/process-agent/subcommands/run/command.go)
    • Security Agent (cmd/security-agent/subcommands/runtime/command.go)
    • System Probe (cmd/system-probe/subcommands/run/command.go)
    • DogStatsD (cmd/dogstatsd/subcommands/start/command.go)

Step 2: Read reference examples from the codebase

Before writing any code, read the appropriate reference files to follow existing patterns exactly.

  1. Read the interface defined in comp/core/settings/component.go to understand the RuntimeSetting methods.

  2. Read an existing implementation matching the chosen value type. Use Glob with pattern pkg/config/settings/runtime_setting_*.go to list available examples, then read one that matches the desired type (boolean, integer, string, etc.).

  3. Read the test file alongside the chosen reference to see the test pattern.

  4. Read a registration site: Look at one of the command.go files listed in Step 1.7 to see how settings are added to the Settings map.

Step 3: Create the RuntimeSetting implementation file

File naming convention: runtime_setting_<feature_name>.go

File location:

  • Shared: pkg/config/settings/runtime_setting_<feature>.go
  • Agent-specific: cmd/agent/subcommands/run/internal/settings/runtime_setting_<feature>.go

Create the implementation following the patterns from the reference file read in Step 2. Every RuntimeSetting needs:

  1. Struct with a ConfigKey string field
  2. Constructor New<Name>RuntimeSetting() that sets the config key
  3. Description() — returns the human-readable description
  4. Hidden() — returns whether hidden from list-runtime
  5. Name() — returns the config key
  6. Get(config) — reads the current value using the appropriate typed getter
  7. Set(config, v, source) — validates/converts the input value, then calls config.Set()

Type conversion in Set(): for Boolean and Integer types, use the GetBool(v) / GetInt(v) helper functions from pkg/config/settings — these handle string-to-type conversion. For agent-specific settings, import the helpers via settings "github.com/DataDog/datadog-agent/pkg/config/settings".

Step 4: Create a unit test file

Create a test file alongside the implementation: runtime_setting_<feature>_test.go

Follow the test patterns from the reference test file read in Step 2. The test should verify:

  • Name(), Description(), Hidden() return expected values
  • Get returns the correct value from config
  • Set with a valid value updates the config
  • Set with a string representation works (e.g. "true"/"false" for bools)
  • Set with an invalid value returns an error

Step 5: Register the setting

Find the settings.Params provider in the appropriate command.go file(s) for each selected service (from Step 1.7). Add the new setting to the Settings map following the existing pattern in that file. The import alias convention and registration format are visible in the existing entries.

Step 6: Verify

  1. Run the new test:

    dda inv test --targets=<package_path>

  2. Run the linter on changed files:

    dda inv linter.go

  3. Report the results to the user. If tests or linting fail, fix the issues.

Important Notes

  • The RuntimeSetting interface is defined in comp/core/settings/component.go
  • Helper functions GetBool and GetInt are in pkg/config/settings/runtime_setting.go
  • All Set methods receive a model.Source parameter for config source tracking — always pass it through to config.Set()
  • Settings are exposed via HTTP at /config/{setting_name} (GET to read, POST to write) and via the CLI: agent config get <setting>, agent config set <setting> <value>, agent config list-runtime
  • Follow existing code style: use the same comment patterns, error formatting, and naming conventions as existing RuntimeSettings

Usage

  • /create-runtime-setting — Interactive: prompts for all details
  • /create-runtime-setting my_new_setting — Pre-fills the setting name, prompts for the rest