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// Copyright 2014 Canonical Ltd.
// Licensed under the AGPLv3, see LICENCE file for details.
package state
import (
"fmt"
"launchpad.net/juju-core/constraints"
"launchpad.net/juju-core/environs/config"
"launchpad.net/juju-core/errors"
)
// Policy is an interface provided to State that may
// be consulted by State to validate or modify the
// behaviour of certain operations.
//
// If a Policy implementation does not implement one
// of the methods, it must return an error that
// satisfies errors.IsNotImplemented, and will thus
// be ignored. Any other error will cause an error
// in the use of the policy.
type Policy interface {
// Prechecker takes a *config.Config and returns
// a (possibly nil) Prechecker or an error.
Prechecker(*config.Config) (Prechecker, error)
// ConfigValidator takes a provider type name and returns
// a (possibly nil) ConfigValidator or an error.
ConfigValidator(providerType string) (ConfigValidator, error)
// EnvironCapability takes a *config.Config and returns
// a (possibly nil) EnvironCapability or an error.
EnvironCapability(*config.Config) (EnvironCapability, error)
// ConstraintsValidator takes a *config.Config and returns
// a (possibly nil) constraints.Validator or an error.
ConstraintsValidator(*config.Config) (constraints.Validator, error)
}
// Prechecker is a policy interface that is provided to State
// to perform pre-flight checking of instance creation.
type Prechecker interface {
// PrecheckInstance performs a preflight check on the specified
// series and constraints, ensuring that they are possibly valid for
// creating an instance in this environment.
//
// PrecheckInstance is best effort, and not guaranteed to eliminate
// all invalid parameters. If PrecheckInstance returns nil, it is not
// guaranteed that the constraints are valid; if a non-nil error is
// returned, then the constraints are definitely invalid.
PrecheckInstance(series string, cons constraints.Value, placement string) error
}
// ConfigValidator is a policy interface that is provided to State
// to check validity of new configuration attributes before applying them to state.
type ConfigValidator interface {
Validate(cfg, old *config.Config) (valid *config.Config, err error)
}
// EnvironCapability implements access to metadata about the capabilities
// of an environment.
type EnvironCapability interface {
// SupportedArchitectures returns the image architectures which can
// be hosted by this environment.
SupportedArchitectures() ([]string, error)
// SupportNetworks returns whether the environment has support to
// specify networks for services and machines.
SupportNetworks() bool
// SupportsUnitAssignment returns an error which, if non-nil, indicates
// that the environment does not support unit placement. If the environment
// does not support unit placement, then machines may not be created
// without units, and units cannot be placed explcitly.
SupportsUnitPlacement() error
}
// precheckInstance calls the state's assigned policy, if non-nil, to obtain
// a Prechecker, and calls PrecheckInstance if a non-nil Prechecker is returned.
func (st *State) precheckInstance(series string, cons constraints.Value, placement string) error {
if st.policy == nil {
return nil
}
cfg, err := st.EnvironConfig()
if err != nil {
return err
}
prechecker, err := st.policy.Prechecker(cfg)
if errors.IsNotImplemented(err) {
return nil
} else if err != nil {
return err
}
if prechecker == nil {
return fmt.Errorf("policy returned nil prechecker without an error")
}
return prechecker.PrecheckInstance(series, cons, placement)
}
func (st *State) constraintsValidator() (constraints.Validator, error) {
// Default behaviour is to simply use a standard validator with
// no environment specific behaviour built in.
defaultValidator := constraints.NewValidator()
if st.policy == nil {
return defaultValidator, nil
}
cfg, err := st.EnvironConfig()
if err != nil {
return nil, err
}
validator, err := st.policy.ConstraintsValidator(cfg)
if errors.IsNotImplemented(err) {
return defaultValidator, nil
} else if err != nil {
return nil, err
}
if validator == nil {
return nil, fmt.Errorf("policy returned nil constraints validator without an error")
}
return validator, nil
}
// resolveConstraints combines the given constraints with the environ constraints to get
// a constraints which will be used to create a new instance.
func (st *State) resolveConstraints(cons constraints.Value) (constraints.Value, error) {
validator, err := st.constraintsValidator()
if err != nil {
return constraints.Value{}, err
}
envCons, err := st.EnvironConstraints()
if err != nil {
return constraints.Value{}, err
}
return validator.Merge(envCons, cons)
}
// validateConstraints returns an error if the given constraints are not valid for the
// current environment, and also any unsupported attributes.
func (st *State) validateConstraints(cons constraints.Value) ([]string, error) {
validator, err := st.constraintsValidator()
if err != nil {
return nil, err
}
return validator.Validate(cons)
}
// validate calls the state's assigned policy, if non-nil, to obtain
// a ConfigValidator, and calls Validate if a non-nil ConfigValidator is
// returned.
func (st *State) validate(cfg, old *config.Config) (valid *config.Config, err error) {
if st.policy == nil {
return cfg, nil
}
configValidator, err := st.policy.ConfigValidator(cfg.Type())
if errors.IsNotImplemented(err) {
return cfg, nil
} else if err != nil {
return nil, err
}
if configValidator == nil {
return nil, fmt.Errorf("policy returned nil configValidator without an error")
}
return configValidator.Validate(cfg, old)
}
// supportsUnitPlacement calls the state's assigned policy, if non-nil,
// to obtain an EnvironCapability, and calls SupportsUnitPlacement if a
// non-nil EnvironCapability is returned.
func (st *State) supportsUnitPlacement() error {
if st.policy == nil {
return nil
}
cfg, err := st.EnvironConfig()
if err != nil {
return err
}
capability, err := st.policy.EnvironCapability(cfg)
if errors.IsNotImplemented(err) {
return nil
} else if err != nil {
return err
}
if capability == nil {
return fmt.Errorf("policy returned nil EnvironCapability without an error")
}
return capability.SupportsUnitPlacement()
}
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