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urlclusteranalyzer.go
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urlclusteranalyzer.go
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/*
* Copyright (c) 2017, MegaEase
* 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.
* 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 urlclusteranalyzer
import (
"strings"
"sync"
lru "github.com/hashicorp/golang-lru"
)
const (
maxValues = 20
maxLayers = 256
)
// URLClusterAnalyzer is url cluster analyzer.
type URLClusterAnalyzer struct {
slots []*field `yaml:"slots"`
mutex *sync.Mutex
cache *lru.Cache
}
type field struct {
constant string `yaml:"constant"`
subFields []*field `yaml:"subFields"`
variableField *field `yaml:"variableField"`
isVariableField bool `yaml:"isVariableField"`
pattern string `yaml:"pattern"`
}
func newField(name string) *field {
f := &field{
constant: name,
subFields: make([]*field, 0),
variableField: nil,
isVariableField: false,
pattern: "",
}
return f
}
// New creates a URLClusterAnalyzer.
func New() *URLClusterAnalyzer {
cache, _ := lru.New(4098)
u := &URLClusterAnalyzer{
mutex: &sync.Mutex{},
slots: make([]*field, maxLayers),
cache: cache,
}
for i := 0; i < maxLayers; i++ {
u.slots[i] = newField("root")
}
return u
}
// GetPattern extracts the pattern of a Restful url path.
// A field of the path occurs more than 20 distinct values will be considered as a variables.
// e.g. input: /com/megaease/users/123/friends/456
// output: /com/megaease/users/*/friends/*
func (u *URLClusterAnalyzer) GetPattern(urlPath string) string {
if urlPath == "" {
return ""
}
if val, ok := u.cache.Get(urlPath); ok {
return val.(string)
}
var values []string
if urlPath[0] == '/' {
values = strings.Split(urlPath[1:], "/")
} else {
values = strings.Split(urlPath, "/")
}
pos := len(values)
if len(values) >= maxLayers {
pos = maxLayers - 1
}
currField := u.slots[pos]
currPattern := currField.pattern
u.mutex.Lock()
defer u.mutex.Unlock()
LOOP:
for i := 0; i < len(values); i++ {
// a known variable field
if currField.isVariableField {
currPattern = currField.pattern
currField = currField.variableField
continue
}
// a known constant field
for _, v := range currField.subFields {
if v.constant == values[i] {
currPattern = v.pattern
currField = v
continue LOOP
}
}
newF := newField(values[i])
currField.subFields = append(currField.subFields, newF)
// find out a new variable field
if len(currField.subFields) > maxValues {
currField.isVariableField = true
currField.variableField = newField("*")
currField.pattern = currPattern + "/*"
currPattern = currField.pattern
currField = currField.variableField
continue
}
// find out a new constant field
newF.pattern = currPattern + "/" + values[i]
currPattern = newF.pattern
currField = newF
}
u.cache.Add(urlPath, currPattern)
return currPattern
}