Config models¶
All integrations use pydantic models as the primary way to validate and interface with configuration.
As config spec data types are based on OpenAPI 3, we automatically generate the necessary code.
The models reside in a package named config_models located at the root of a check's namespaced package. For example, a new integration named foo:
foo
│ ...
├── datadog_checks
│ └── foo
│ └── config_models
│ ├── __init__.py
│ ├── defaults.py
│ ├── instance.py
│ ├── shared.py
│ └── validators.py
│ └── __init__.py
│ ...
...
There are 2 possible models:
InstanceConfig(ID:instance) that corresponds to a check's entry in theinstancessectionSharedConfig(ID:shared) that corresponds to theinit_configsection that is shared by all instances
All models are defined in <ID>.py and are available for import directly under config_models.
Default values¶
The default values for optional settings are populated in defaults.py and are derived from the value property of config spec options. The precedence is the default key followed by the example key (if it appears to represent a real value rather than an illustrative example and the type is a primitive). In all other cases, the default is None, which means there is no default getter function.
Validation¶
The validation of fields for every model occurs in three high-level stages, as described in this section.
Initial¶
def initialize_<ID>(values: dict[str, Any], **kwargs) -> dict[str, Any]:
...
If such a validator exists in validators.py, then it is called once with the raw config that was supplied by the user. The returned mapping is used as the input config for the subsequent stages.
Field¶
The value of each field goes through the following steps.
Default value population¶
If a field was not supplied by the user nor during the initialization stage, then its default value is taken from defaults.py. This stage is skipped for required fields.
Custom field validators¶
The contents of validators.py are entirely custom and contain functions to perform extra validation if necessary.
def <ID>_<OPTION_NAME>(value: Any, *, field: pydantic.fields.FieldInfo, **kwargs) -> Any:
...
Such validators are called for the appropriate field of the proper model. The returned value is used as the new value of the option for the subsequent stages.
Note
This only occurs if the option was supplied by the user.
Pre-defined field validators¶
A validators key under the value property of config spec options is considered. Every entry refers to a relative import path to a field validator under datadog_checks.base.utils.models.validation and is executed in the defined order.
Note
This only occurs if the option was supplied by the user.
Conversion to immutable types¶
Every list is converted to tuple and every dict is converted to types.MappingProxyType.
Note
A field or nested field would only be a dict when it is defined as a mapping with arbitrary keys. Otherwise, it would be a model with its own properties as usual.
Final¶
def check_<ID>(model: pydantic.BaseModel) -> pydantic.BaseModel:
...
If such a validator exists in validators.py, then it is called with the final constructed model. At this point, it cannot be mutated, so you can only raise errors.
Loading¶
A check initialization occurs before a check's first run that loads the config models. Validation errors will thus prevent check execution.
Interface¶
The config models package contains a class ConfigMixin from which checks inherit:
from datadog_checks.base import AgentCheck
from .config_models import ConfigMixin
class Check(AgentCheck, ConfigMixin):
...
It exposes the instantiated InstanceConfig model as self.config and SharedConfig model as self.shared_config.
Immutability¶
In addition to each field being converted to an immutable type, all generated models are configured as immutable.
Deprecation¶
Every option marked as deprecated in the config spec will log a warning with information about when it will be removed and what to do.
Enforcement¶
A validation command validate models runs in our CI. To locally generate the proper files, run ddev validate models [INTEGRATION] --sync.