graph/merge_duplicates.go
// Copyright © 2016 Asteris, LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License 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 graph
import (
"strings"
"sync"
"github.com/asteris-llc/converge/graph/node"
"github.com/asteris-llc/converge/helpers/logging"
"github.com/mitchellh/hashstructure"
"golang.org/x/net/context"
)
// SkipMergeFunc will be used to determine whether or not to merge a node
type SkipMergeFunc func(*node.Node) bool
// MergeDuplicates removes duplicates in the graph
func MergeDuplicates(ctx context.Context, g *Graph, skip SkipMergeFunc) (*Graph, error) {
lock := new(sync.Mutex)
values := map[uint64]string{}
logger := logging.GetLogger(ctx).WithField("function", "MergeDuplicates")
return g.RootFirstTransform(ctx, func(meta *node.Node, out *Graph) error {
if IsRoot(meta.ID) {
return nil
}
if skip(meta) {
logger.WithField("id", meta.ID).Debug("skipping by request")
return nil
}
if meta.Value() == nil {
return nil // not much use in hashing a nil value
}
lock.Lock()
defer lock.Unlock()
hash, err := hashstructure.Hash(meta.Value(), nil)
if err != nil {
return err
}
// if we haven't seen this value before, register it and return
target, ok := values[hash]
if !ok {
logger.WithField("id", meta.ID).Debug("registering as original")
values[hash] = meta.ID
return nil
}
logger.WithField("id", target).WithField("duplicate", meta.ID).Debug("found duplicate")
// Point all inbound links to value to target instead
for _, src := range Sources(g.UpEdges(meta.ID)) {
logger.WithField("src", src).WithField("duplicate", meta.ID).WithField("target", target).Debug("re-pointing dependency")
out.Disconnect(src, meta.ID)
out.Connect(src, target)
}
// Remove children and their edges
for _, child := range g.Descendents(meta.ID) {
logger.WithField("child", child).Debug("removing child")
out.Remove(child)
}
// Remove value
out.Remove(meta.ID)
return nil
})
}
// helper functions for various things we need to merge.
// TODO: find a better home
// SkipModuleAndParams skips trimming modules and params
func SkipModuleAndParams(meta *node.Node) bool {
base := BaseID(meta.ID)
_, isConditional := meta.LookupMetadata("conditional-switch-name")
return strings.HasPrefix(base, "module") || strings.HasPrefix(base, "param") || isConditional
}