func (st *State) constraintsValidator() (constraints.Validator, error) {
// Default behaviour is to simply use a standard validator with
// no model specific behaviour built in.
var validator constraints.Validator
if st.policy != nil {
var err error
validator, err = st.policy.ConstraintsValidator()
if errors.IsNotImplemented(err) {
validator = constraints.NewValidator()
} else if err != nil {
return nil, err
} else if validator == nil {
return nil, errors.New("policy returned nil constraints validator without an error")
}
} else {
validator = constraints.NewValidator()
}
// Add supported architectures gleaned from cloud image
// metadata to the validator's vocabulary.
model, err := st.Model()
if err != nil {
return nil, errors.Annotate(err, "getting model")
}
if region := model.CloudRegion(); region != "" {
cfg, err := st.ModelConfig()
if err != nil {
return nil, errors.Trace(err)
}
arches, err := st.CloudImageMetadataStorage.SupportedArchitectures(
cloudimagemetadata.MetadataFilter{
Stream: cfg.AgentStream(),
Region: region,
},
)
if err != nil {
return nil, errors.Annotate(err, "querying supported architectures")
}
if len(arches) != 0 {
validator.UpdateVocabulary(constraints.Arch, arches)
}
}
return validator, nil
}
