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detect backtracking

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Signed-off-by: Wangchong Zhou <fffonion@gmail.com>
This commit is contained in:
Wangchong Zhou 2018-09-12 14:44:07 -07:00
parent bfe23298aa
commit dad04e9c8b
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GPG key ID: B607274584E8D5E5
2 changed files with 172 additions and 31 deletions
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178
pkg/mapper/mapper.go
View file

@ -40,24 +40,29 @@ var (
)
type mapperConfigDefaults struct {
TimerType TimerType `yaml:"timer_type"`
Buckets []float64 `yaml:"buckets"`
Quantiles []metricObjective `yaml:"quantiles"`
MatchType MatchType `yaml:"match_type"`
TimerType TimerType `yaml:"timer_type"`
Buckets []float64 `yaml:"buckets"`
Quantiles []metricObjective `yaml:"quantiles"`
MatchType MatchType `yaml:"match_type"`
GlobDisbleOrdering bool `yaml:"glob_disable_ordering"`
}
type mappingState struct {
transitionsMap map[string]*mappingState
transitionsArray []*mappingState
// use to compare length upfront to avoid unnecessary backtrack
minRemainingLength int
maxRemainingLength int
// result is nil unless there's a metric ends with this state
result *MetricMapping
}
type MetricMapper struct {
Defaults mapperConfigDefaults `yaml:"defaults"`
Mappings []MetricMapping `yaml:"mappings"`
FSM *mappingState
// if this is true, that means at least one matching rule is regex type
Defaults mapperConfigDefaults `yaml:"defaults"`
Mappings []MetricMapping `yaml:"mappings"`
FSM *mappingState
FSMNeedsBacktracking bool
// if doRegex is true, at least one matching rule is regex type
doRegex bool
dumpFSMPath string
mutex sync.Mutex
@ -71,6 +76,11 @@ type templateFormatter struct {
fmtString string
}
type fsmBacktrackRecord struct {
fieldIndex int
state *mappingState
}
type matchMetricType string
type MetricMapping struct {
@ -142,6 +152,20 @@ func formatTemplate(formatter templateFormatter, captures map[int]string) string
}
}
func min(x, y int) int {
if x < y {
return x
}
return y
}
func max(x, y int) int {
if x > y {
return x
}
return y
}
func (m *MetricMapper) InitFromYAMLString(fileContents string) error {
var n MetricMapper
@ -164,7 +188,12 @@ func (m *MetricMapper) InitFromYAMLString(fileContents string) error {
maxPossibleTransitions := len(n.Mappings)
n.FSM = &mappingState{}
n.FSM.transitionsMap = make(map[string]*mappingState, maxPossibleTransitions)
n.FSM.transitionsMap = make(map[string]*mappingState, 3)
for _, field := range []MetricType{MetricTypeCounter, MetricTypeTimer, MetricTypeGauge, ""} {
state := &mappingState{}
(*state).transitionsMap = make(map[string]*mappingState, maxPossibleTransitions)
n.FSM.transitionsMap[string(field)] = state
}
for i := range n.Mappings {
maxPossibleTransitions--
@ -202,25 +231,40 @@ func (m *MetricMapper) InitFromYAMLString(fileContents string) error {
// first split by "."
matchFields := strings.Split(currentMapping.Match, ".")
// fill into our FSM
root := n.FSM
captureCount := 0
for i, field := range matchFields {
state, prs := root.transitionsMap[field]
if !prs {
state = &mappingState{}
(*state).transitionsMap = make(map[string]*mappingState, maxPossibleTransitions)
root.transitionsMap[field] = state
// if this is last field, set result to currentMapping instance
if i == len(matchFields)-1 {
root.transitionsMap[field].result = currentMapping
roots := []*mappingState{}
if currentMapping.MatchMetricType == "" {
for _, metricType := range []MetricType{MetricTypeCounter, MetricTypeTimer, MetricTypeGauge, ""} {
roots = append(roots, n.FSM.transitionsMap[string(metricType)])
}
} else {
roots = append(roots, n.FSM.transitionsMap[string(currentMapping.MatchMetricType)])
}
var captureCount int
for _, root := range roots {
captureCount = 0
for i, field := range matchFields {
state, prs := root.transitionsMap[field]
if !prs {
state = &mappingState{}
(*state).transitionsMap = make(map[string]*mappingState, maxPossibleTransitions)
(*state).maxRemainingLength = len(matchFields) - i - 1
(*state).minRemainingLength = len(matchFields) - i - 1
root.transitionsMap[field] = state
// if this is last field, set result to currentMapping instance
if i == len(matchFields)-1 {
root.transitionsMap[field].result = currentMapping
}
} else {
(*state).maxRemainingLength = max(len(matchFields)-i-1, (*state).maxRemainingLength)
(*state).minRemainingLength = min(len(matchFields)-i-1, (*state).minRemainingLength)
}
if field == "*" {
captureCount++
}
}
if field == "*" {
captureCount++
}
// goto next state
root = state
// goto next state
root = state
}
}
nameFmt, err := generateFormatter(currentMapping.Name, captureCount)
if err != nil {
@ -243,7 +287,7 @@ func (m *MetricMapper) InitFromYAMLString(fileContents string) error {
} else {
currentMapping.regex = regex
}
m.doRegex = true
n.doRegex = true
} /*else if currentMapping.MatchType == MatchTypeGlob {
if !metricLineRE.MatchString(currentMapping.Match) {
return fmt.Errorf("invalid match: %s", currentMapping.Match)
@ -280,9 +324,22 @@ func (m *MetricMapper) InitFromYAMLString(fileContents string) error {
m.Mappings = n.Mappings
if len(n.FSM.transitionsMap) > 0 || len(n.FSM.transitionsArray) > 0 {
m.FSM = n.FSM
m.doRegex = n.doRegex
if m.dumpFSMPath != "" {
dumpFSM(m.dumpFSMPath, m.FSM)
}
// backtracking only makes sense when we disbled ordering of rules
// where transistions are stored in (unordered) map
if m.Defaults.GlobDisbleOrdering || true {
backtrackingRules := findBacktrackRules(&n)
if len(backtrackingRules) > 0 {
for _, rule := range backtrackingRules {
log.Infof("backtracking required for match \"%s\", matching performance may be degraded\n", rule)
}
m.FSMNeedsBacktracking = true
}
}
}
if m.MappingsCount != nil {
@ -297,6 +354,58 @@ func (m *MetricMapper) SetDumpFSMPath(path string) error {
return nil
}
func findBacktrackRules(n *MetricMapper) []string {
var found []string
// rule A and B that has same length and
// A one has * in rules but is not a superset of B makes it needed for backtracking
ruleByLength := make(map[int][]string)
ruleREByLength := make(map[int][]*regexp.Regexp)
// first sort rules by length
for _, mapping := range n.Mappings {
if mapping.MatchType != MatchTypeGlob {
continue
}
l := len(mapping.Match)
ruleByLength[l] = append(ruleByLength[l], mapping.Match)
metricRe := strings.Replace(mapping.Match, ".", "\\.", -1)
metricRe = strings.Replace(metricRe, "*", "([^.]*)", -1)
regex, err := regexp.Compile("^" + metricRe + "$")
if err != nil {
log.Warnf("invalid match %s. cannot compile regex in mapping: %v", mapping.Match, err)
}
ruleREByLength[l] = append(ruleREByLength[l], regex)
}
for l, rules := range ruleByLength {
if len(rules) == 1 {
continue
}
rulesRE := ruleREByLength[l]
// for each rule r1 in rules that has * inside, check if r1 is the superset of any rules
// if not then r1 is a rule that leads to backtrack
for i1, r1 := range rules {
hasSubset := false
re1 := rulesRE[i1]
if re1 == nil || strings.Index(r1, "*") == -1 {
continue
}
for _, r2 := range rules {
if r2 != r1 && len(re1.FindStringSubmatchIndex(r2)) > 0 {
fmt.Println("subset", r1, "of", r2)
hasSubset = true
break
}
}
if !hasSubset {
found = append(found, r1)
}
}
}
return found
}
func dumpFSM(fileName string, root *mappingState) {
log.Infoln("Start dumping FSM to", fileName)
idx := 0
@ -313,13 +422,18 @@ func dumpFSM(fileName string, root *mappingState) {
for field, transition := range states[idx].transitionsMap {
states[len(states)] = transition
w.WriteString(fmt.Sprintf("%d -> %d [label = \"%s\"];\n", idx, len(states)-1, field))
if transition.transitionsMap == nil || len(transition.transitionsMap) == 0 {
if idx == 0 {
// color for metric types
w.WriteString(fmt.Sprintf("%d [color=\"#D6B656\",fillcolor=\"#FFF2CC\"];\n", len(states)-1))
} else if transition.transitionsMap == nil || len(transition.transitionsMap) == 0 {
// color for end state
w.WriteString(fmt.Sprintf("%d [color=\"#82B366\",fillcolor=\"#D5E8D4\"];\n", len(states)-1))
}
}
idx++
}
w.WriteString(fmt.Sprintf("0 [color=\"#D6B656\",fillcolor=\"#FFF2CC\"];\n"))
// color for start state
w.WriteString(fmt.Sprintf("0 [color=\"#a94442\",fillcolor=\"#f2dede\"];\n"))
w.WriteString("}")
w.Flush()
log.Infoln("Finish dumping FSM")
@ -336,6 +450,7 @@ func (m *MetricMapper) InitFromFile(fileName string) error {
func (m *MetricMapper) GetMapping(statsdMetric string, statsdMetricType MetricType) (*MetricMapping, prometheus.Labels, bool) {
// glob matching
if root := m.FSM; root != nil {
root = root.transitionsMap[string(statsdMetricType)]
matchFields := strings.Split(statsdMetric, ".")
captures := make(map[int]string, len(matchFields))
captureIdx := 0
@ -345,9 +460,10 @@ func (m *MetricMapper) GetMapping(statsdMetric string, statsdMetricType MetricTy
break
}
state, prs := root.transitionsMap[field]
if !prs {
fieldsLeft := filedsCount - i - 1
if !prs || fieldsLeft > state.maxRemainingLength || fieldsLeft < state.minRemainingLength {
state, prs = root.transitionsMap["*"]
if !prs {
if !prs || fieldsLeft > state.maxRemainingLength || fieldsLeft < state.minRemainingLength {
break
}
captures[captureIdx] = field

25
pkg/mapper/mapper_test.go
View file

@ -471,6 +471,31 @@ mappings:
},
},
},
//Config with backtracking
{
config: `mappings:
- match: foo.*.ccc
name: "fooc"
labels: {}
- match: foo.bbb.aaa
name: "foob"
labels: {}
`,
mappings: mappings{
"foo.bbb.ccc": {
name: "fooc",
labels: map[string]string{},
},
"foo.ddd.ccc": {
name: "fooc",
labels: map[string]string{},
},
"foo.bbb.aaa": {
name: "foob",
labels: map[string]string{},
},
},
},
}
mapper := MetricMapper{}