fettle v1.0.0 Fettle.Config View Source

Processes configuration for healthchecks into internal structures.

Configuration can be specified either by application configuration under the :fettle key, or by supplying via a module, function or inline argument to Fettle.Supervisor.start_link/1.

  config :fettle,
    system_code: :my_app, # NB mandatory
    name: "My Application",
    description: "My Application provides...",
    panic_guide_url: "https://stackoverflow.com",
    initial_delay_ms: 1_000,
    period_ms: 30_000,
    timeout_ms: 2_000,
    checks: [ ... ]

The minimum configuration requires the system_code key:

Key	Description	Required or Defaults
`system_code`	System code for report	Required
`schema`	Module for report generation	`Fettle.Schema.FTHealthCheckV1`
`name`	Human-readable name of system	defaults to `system_code`
`description`	Human-readable description of system	defaults to `system_code`
`initial_delay_ms`	Number of milliseconds to wait before running first check	`0`
`period_ms`	Number of milliseconds to wait between runs of the same check	`30_000`
`timeout_ms`	Number of milliseconds to wait before timing-out a running check	`5000`
`panic_guide_url`	URL of documentation for check	¹ ²
`business_impact`	Which business function is affected?	¹
`technical_summary`	Technical description for Ops	¹
`checks`	An array of pre-configured health-check config	Optional, see `Fettle.add/3` ³

Specifies default value for checks. Required only if not specified for every check.
panic_guide_url can form the base-url for checks which specify a relative panic_guide_url.
checks is an array, but each element can be specified as either a map, or a Keyword list (or any other Enumerable that yields key-value pairs).

Link to this section Summary

Types

spec_and_mod()

Tuple which specifies a check (derived from app config)

t()

Top-level configuration for global settings and check defaults (derived from app config)

Functions

check_from_config(check, config)

Convert a single health check specification from config into a Fettle.Spec spec, with module and args

default_keys(config, key_defaults)

default missing, nil or empty keys to matching values in keyword list

ensure_keys!(config, required_keys)

ensure required keys are not missing, null, or empty strings

interpolate_panic_guide_url(spec, config_url)

append path parts to top-level config panic_guide_url if relative path is given in checker

to_app_config(map_or_kws)

Parses configuration into %Fettle.Config{}

Link to this section Types

spec_and_mod()

spec_and_mod() :: {Fettle.Spec.t(), module(), init_args :: any()}

Tuple which specifies a check (derived from app config)

t()

t() :: %Fettle.Config{
  business_impact: String.t(),
  description: atom() | String.t(),
  initial_delay_ms: integer(),
  name: atom() | String.t(),
  panic_guide_url: String.t(),
  period_ms: integer(),
  schema: atom(),
  system_code: atom() | String.t(),
  technical_summary: String.t(),
  timeout_ms: integer()
}

Top-level configuration for global settings and check defaults (derived from app config)

Link to this section Functions

check_from_config(check, config)

check_from_config(check :: map() | list(), config :: Fettle.Config.t()) ::
  spec_and_mod()

Convert a single health check specification from config into a Fettle.Spec spec, with module and args.

Each check is specified as a collection of key-value pairs:

Key	Type	Description	Default/Required
`name`	`String`	Name of check	required
`id`	`String`	Short id of check	Defaults to `name`
`description`	`String`	Longer description of check	Defaults to `name`
`panic_guide_url`	`String`	URL of documentation for check	Defaults to config
`business_impact`	`String`	Which business function is affected?	Defaults to config
`technical_summary`	`String`	Technical description for Ops	Defaults to config
`severity`	`1-3`	Severity level: 1 high, 3 low	Defaults to `1`
`initial_delay_ms`	`integer`	Number of milliseconds to wait before running first check	Defaults to config
`period_ms`	`integer`	Number of milliseconds to wait between runs of the check	Defaults to config
`timeout_ms`	`integer`	Number of milliseconds to wait before timing-out check	Defaults to config
`checker`	`atom`	`Fettle.Checker` module	Required
`args`	`any`	passed as argument for `Fettle.Checker` module	defaults to []

Some fields of the check can be omitted, and the default value from the top-level config will be used instead; this applies to all fields except name, full_name, id and severity; if id is omitted, name will be used, if full_name is omitted, name will be used; severity defaults to 1.

panic_guide_url has special behavior, in that if a path starting with # or / is given, then this is appended to the panic_guide_url in the top-level configuration properties.

config :health,
  system_code: "service-a",
  schema: Fettle.Schema.FTHealthCheckV1,
  panic_guide_url: "http://co.com/docs/service/healthchecks",
  technical_summary: "We'll spend all week repairing the damage.",
  checks: [
    %{
      name: "service-b", # also provides id and full_name if those undefined
      panic_guide_url: "#service-b", # appended to top-level url
      # technical_summary will come from top-level
      business_impact: "No sales",
      period_ms: 10_000, # override default for this check only
      checker: MyHealth.Spec, # implementation module name
      args: [url: "https://service-b.co.com/__gtg"] # for `Fettle.Checker.check/1`
    },
    %{
      ...
    }
  ]