mirror of
https://github.com/prometheus/statsd_exporter.git
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324 lines
10 KiB
Go
324 lines
10 KiB
Go
// Copyright 2018 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package fsm
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import (
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"regexp"
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"strings"
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"github.com/prometheus/common/log"
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)
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type mappingState struct {
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transitions map[string]*mappingState
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minRemainingLength int
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maxRemainingLength int
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// result* members are nil unless there's a metric ends with this state
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Result interface{}
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ResultPriority int
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}
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type fsmBacktrackStackCursor struct {
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fieldIndex int
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captureIndex int
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currentCapture string
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state *mappingState
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prev *fsmBacktrackStackCursor
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next *fsmBacktrackStackCursor
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}
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type FSM struct {
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root *mappingState
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metricTypes []string
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statesCount int
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BacktrackingNeeded bool
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OrderingDisabled bool
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}
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// NewFSM creates a new FSM instance
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func NewFSM(metricTypes []string, maxPossibleTransitions int, orderingDisabled bool) *FSM {
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fsm := FSM{}
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root := &mappingState{}
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root.transitions = make(map[string]*mappingState, len(metricTypes))
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for _, field := range metricTypes {
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state := &mappingState{}
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(*state).transitions = make(map[string]*mappingState, maxPossibleTransitions)
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root.transitions[string(field)] = state
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}
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fsm.OrderingDisabled = orderingDisabled
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fsm.metricTypes = metricTypes
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fsm.statesCount = 0
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fsm.root = root
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return &fsm
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}
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// AddState adds a mapping rule into the existing FSM.
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// The maxPossibleTransitions parameter sets the expected count of transitions left.
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// The result parameter sets the generic type to be returned when fsm found a match in GetMapping.
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func (f *FSM) AddState(match string, matchMetricType string, maxPossibleTransitions int, result interface{}) int {
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// first split by "."
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matchFields := strings.Split(match, ".")
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// fill into our FSM
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roots := []*mappingState{}
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// first state is the metric type
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if matchMetricType == "" {
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// if metricType not specified, connect the start state from all three types
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for _, metricType := range f.metricTypes {
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roots = append(roots, f.root.transitions[string(metricType)])
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}
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} else {
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roots = append(roots, f.root.transitions[matchMetricType])
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}
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var captureCount int
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var finalStates []*mappingState
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// iterating over different start state (different metric types)
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for _, root := range roots {
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captureCount = 0
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// for each start state, connect from start state to end state
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for i, field := range matchFields {
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state, prs := root.transitions[field]
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if !prs {
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// create a state if it's not exist in the fsm
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state = &mappingState{}
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(*state).transitions = make(map[string]*mappingState, maxPossibleTransitions)
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(*state).maxRemainingLength = len(matchFields) - i - 1
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(*state).minRemainingLength = len(matchFields) - i - 1
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root.transitions[field] = state
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// if this is last field, set result to currentMapping instance
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if i == len(matchFields)-1 {
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root.transitions[field].Result = result
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}
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} else {
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(*state).maxRemainingLength = max(len(matchFields)-i-1, (*state).maxRemainingLength)
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(*state).minRemainingLength = min(len(matchFields)-i-1, (*state).minRemainingLength)
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}
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if field == "*" {
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captureCount++
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}
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// goto next state
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root = state
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}
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finalStates = append(finalStates, root)
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}
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for _, state := range finalStates {
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state.ResultPriority = f.statesCount
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}
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f.statesCount++
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return captureCount
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}
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// GetMapping using the fsm to find matching rules according to given statsdMetric and statsdMetricType.
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// If it finds a match, the final state and the captured strings are returned;
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// if there's no match found, nil and a empty list will be returned.
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func (f *FSM) GetMapping(statsdMetric string, statsdMetricType string) (*mappingState, []string) {
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matchFields := strings.Split(statsdMetric, ".")
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currentState := f.root.transitions[statsdMetricType]
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// the cursor/pointer in the backtrack stack implemented as a double-linked list
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var backtrackCursor *fsmBacktrackStackCursor
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resumeFromBacktrack := false
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// the return variable
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var finalState *mappingState
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captures := make([]string, len(matchFields))
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// keep track of captured group so we don't need to do append() on captures
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captureIdx := 0
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filedsCount := len(matchFields)
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i := 0
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var state *mappingState
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for { // the loop for backtracking
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for { // the loop for a single "depth only" search
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var present bool
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// if we resume from backtrack, we should skip this branch in this case
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// since the state that were saved at the end of this branch
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if !resumeFromBacktrack {
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if len(currentState.transitions) > 0 {
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field := matchFields[i]
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state, present = currentState.transitions[field]
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fieldsLeft := filedsCount - i - 1
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// also compare length upfront to avoid unnecessary loop or backtrack
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if !present || fieldsLeft > state.maxRemainingLength || fieldsLeft < state.minRemainingLength {
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state, present = currentState.transitions["*"]
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if !present || fieldsLeft > state.maxRemainingLength || fieldsLeft < state.minRemainingLength {
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break
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} else {
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captures[captureIdx] = field
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captureIdx++
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}
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} else if f.BacktrackingNeeded {
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// if backtracking is needed, also check for alternative transition, i.e. *
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altState, present := currentState.transitions["*"]
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if !present || fieldsLeft > altState.maxRemainingLength || fieldsLeft < altState.minRemainingLength {
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} else {
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// push to backtracking stack
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newCursor := fsmBacktrackStackCursor{prev: backtrackCursor, state: altState,
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fieldIndex: i,
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captureIndex: captureIdx, currentCapture: field,
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}
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// if this is not the first time, connect to the previous cursor
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if backtrackCursor != nil {
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backtrackCursor.next = &newCursor
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}
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backtrackCursor = &newCursor
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}
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}
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} else {
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// no more transitions for this state
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break
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}
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} // backtrack will resume from here
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// do we reach a final state?
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if state.Result != nil && i == filedsCount-1 {
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if f.OrderingDisabled {
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finalState = state
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return finalState, captures
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} else if finalState == nil || finalState.ResultPriority > state.ResultPriority {
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// if we care about ordering, try to find a result with highest prioity
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finalState = state
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}
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break
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}
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i++
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if i >= filedsCount {
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break
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}
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resumeFromBacktrack = false
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currentState = state
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}
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if backtrackCursor == nil {
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// if we are not doing backtracking or all path has been travesaled
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break
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} else {
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// pop one from stack
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state = backtrackCursor.state
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currentState = state
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i = backtrackCursor.fieldIndex
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captureIdx = backtrackCursor.captureIndex + 1
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// put the * capture back
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captures[captureIdx-1] = backtrackCursor.currentCapture
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backtrackCursor = backtrackCursor.prev
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if backtrackCursor != nil {
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// deref for GC
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backtrackCursor.next = nil
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}
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resumeFromBacktrack = true
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}
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}
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return finalState, captures
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}
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// TestIfNeedBacktracking tests if backtrack is needed for given list of mappings
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// and whether ordering is disabled.
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func TestIfNeedBacktracking(mappings []string, orderingDisabled bool) bool {
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backtrackingNeeded := false
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// A has * in rules, but there's other transisitions at the same state,
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// this makes A the cause of backtracking
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ruleByLength := make(map[int][]string)
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ruleREByLength := make(map[int][]*regexp.Regexp)
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// first sort rules by length
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for _, mapping := range mappings {
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l := len(strings.Split(mapping, "."))
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ruleByLength[l] = append(ruleByLength[l], mapping)
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metricRe := strings.Replace(mapping, ".", "\\.", -1)
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metricRe = strings.Replace(metricRe, "*", "([^.]*)", -1)
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regex, err := regexp.Compile("^" + metricRe + "$")
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if err != nil {
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log.Warnf("invalid match %s. cannot compile regex in mapping: %v", mapping, err)
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}
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// put into array no matter there's error or not, we will skip later if regex is nil
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ruleREByLength[l] = append(ruleREByLength[l], regex)
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}
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for l, rules := range ruleByLength {
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if len(rules) == 1 {
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continue
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}
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rulesRE := ruleREByLength[l]
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for i1, r1 := range rules {
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currentRuleNeedBacktrack := false
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re1 := rulesRE[i1]
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if re1 == nil || strings.Index(r1, "*") == -1 {
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continue
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}
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// if rule r1 is A.B.C.*.E.*, is there a rule r2 is A.B.C.D.x.x or A.B.C.*.E.F ? (x is any string or *)
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// if such r2 exists, then to match r1 we will need backtracking
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for index := 0; index < len(r1); index++ {
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if r1[index] != '*' {
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continue
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}
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// translate the substring of r1 from 0 to the index of current * into regex
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// A.B.C.*.E.* will becomes ^A\.B\.C\. and ^A\.B\.C\.\*\.E\.
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reStr := strings.Replace(r1[:index], ".", "\\.", -1)
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reStr = strings.Replace(reStr, "*", "\\*", -1)
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re := regexp.MustCompile("^" + reStr)
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for i2, r2 := range rules {
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if i2 == i1 {
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continue
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}
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if len(re.FindStringSubmatchIndex(r2)) > 0 {
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currentRuleNeedBacktrack = true
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break
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}
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}
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}
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for i2, r2 := range rules {
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if i2 != i1 && len(re1.FindStringSubmatchIndex(r2)) > 0 {
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// log if we care about ordering and the superset occurs before
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if !orderingDisabled && i1 < i2 {
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log.Warnf("match \"%s\" is a super set of match \"%s\" but in a lower order, "+
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"the first will never be matched", r1, r2)
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}
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currentRuleNeedBacktrack = false
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}
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}
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for i2, re2 := range rulesRE {
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if i2 == i1 || re2 == nil {
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continue
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}
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// if r1 is a subset of other rule, we don't need backtrack
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// because either we turned on ordering
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// or we disabled ordering and can't match it even with backtrack
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if len(re2.FindStringSubmatchIndex(r1)) > 0 {
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currentRuleNeedBacktrack = false
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}
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}
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if currentRuleNeedBacktrack {
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log.Warnf("backtracking required because of match \"%s\", "+
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"matching performance may be degraded", r1)
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backtrackingNeeded = true
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}
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}
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}
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// backtracking will always be needed if ordering of rules is not disabled
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// since transistions are stored in (unordered) map
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// note: don't move this branch to the beginning of this function
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// since we need logs for superset rules
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return !orderingDisabled || backtrackingNeeded
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}
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