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environment_stm_applier.go
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environment_stm_applier.go
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// Copyright 2016-2017 Amazon.com, Inc. or its affiliates. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License"). You may
// not use this file except in compliance with the License. A copy of the
// License is located at
//
// http://aws.amazon.com/apache2.0/
//
// or in the "license" file accompanying this file. This file is distributed
// on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
// express or implied. See the License for the specific language governing
// permissions and limitations under the License.
package store
import (
"github.com/blox/blox/daemon-scheduler/pkg/environment/types"
"github.com/blox/blox/daemon-scheduler/pkg/json"
"github.com/coreos/etcd/clientv3/concurrency"
"github.com/pkg/errors"
)
// EnvironmentSTMApplier supports transactional updates to an environment
type EnvironmentSTMApplier struct {
// environment key
key string
// function that validates the environment currently in the datastore and
// returns the updated environment to be put into the datastore
validateAndUpdateEnv func(*types.Environment) (*types.Environment, error)
}
// updateEnvironment performs the following 3 steps as part of a transaction
// 1. Get existing environment from datastore
// 2. Validate environment retrieved from the datastore & update environment
// 3. Put updated environment into datastore
func (envApplier EnvironmentSTMApplier) updateEnvironment(stm concurrency.STM) error {
err := envApplier.validateApplier()
if err != nil {
return err
}
existingEnvJSON := stm.Get(envApplier.key)
existingEnv, err := envApplier.unmarshalEnv(existingEnvJSON)
if err != nil {
return err
}
updatedEnv, err := envApplier.validateAndUpdateEnv(existingEnv)
if err != nil {
return err
}
if updatedEnv == nil {
return errors.New("Environment to be updated cannot be nil")
}
updatedEnvJSON, err := envApplier.marshalEnv(*updatedEnv)
if err != nil {
return err
}
stm.Put(envApplier.key, updatedEnvJSON)
return nil
}
func (envApplier EnvironmentSTMApplier) unmarshalEnv(envJSON string) (*types.Environment, error) {
if len(envJSON) == 0 {
return nil, nil
}
var env *types.Environment
err := json.UnmarshalJSON(envJSON, &env)
if err != nil {
return nil, errors.Wrapf(err, "Error unmarshaling environment JSON '%s'", envJSON)
}
return env, nil
}
func (envApplier EnvironmentSTMApplier) marshalEnv(env types.Environment) (string, error) {
envJSON, err := json.MarshalJSON(env)
if err != nil {
return "", errors.Wrapf(err, "Error marshaling environment '%v'", env)
}
return envJSON, nil
}
func (envApplier EnvironmentSTMApplier) validateApplier() error {
if envApplier.key == "" {
return errors.New("Environment key has to be initialized")
}
if envApplier.validateAndUpdateEnv == nil {
return errors.New("Environment validate and update funtion has to be initialized")
}
return nil
}