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filter.go
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filter.go
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package log
import (
"bytes"
"fmt"
"unicode"
"unicode/utf8"
"github.com/grafana/loki/pkg/util"
"github.com/grafana/regexp"
"github.com/grafana/regexp/syntax"
"github.com/prometheus/prometheus/model/labels"
)
// Filterer is a interface to filter log lines.
type Filterer interface {
Filter(line []byte) bool
ToStage() Stage
}
// LineFilterFunc is a syntax sugar for creating line filter from a function
type FiltererFunc func(line []byte) bool
func (f FiltererFunc) Filter(line []byte) bool {
return f(line)
}
type trueFilter struct{}
func (trueFilter) Filter(_ []byte) bool { return true }
func (trueFilter) ToStage() Stage { return NoopStage }
// TrueFilter is a filter that returns and matches all log lines whatever their content.
var TrueFilter = trueFilter{}
type existsFilter struct{}
func (e existsFilter) Filter(line []byte) bool {
return len(line) > 0
}
func (e existsFilter) ToStage() Stage {
return StageFunc{
process: func(_ int64, line []byte, _ *LabelsBuilder) ([]byte, bool) {
return line, e.Filter(line)
},
}
}
// ExistsFilter is a filter that returns and matches when a line has any characters.
var ExistsFilter = existsFilter{}
type notFilter struct {
Filterer
}
func (n notFilter) Filter(line []byte) bool {
return !n.Filterer.Filter(line)
}
func (n notFilter) ToStage() Stage {
return StageFunc{
process: func(_ int64, line []byte, _ *LabelsBuilder) ([]byte, bool) {
return line, n.Filter(line)
},
}
}
// newNotFilter creates a new filter which matches only if the base filter doesn't match.
// If the base filter is a `or` it will recursively simplify with `and` operations.
func newNotFilter(base Filterer) Filterer {
// not(a|b) = not(a) and not(b) , and operation can't benefit from this optimization because both legs always needs to be executed.
if or, ok := base.(orFilter); ok {
return NewAndFilter(newNotFilter(or.left), newNotFilter(or.right))
}
return notFilter{Filterer: base}
}
type andFilter struct {
left Filterer
right Filterer
}
// NewAndFilter creates a new filter which matches only if left and right matches.
func NewAndFilter(left Filterer, right Filterer) Filterer {
// Make sure we take care of panics in case a nil or noop filter is passed.
if right == nil || right == TrueFilter {
return left
}
if left == nil || left == TrueFilter {
return right
}
return andFilter{
left: left,
right: right,
}
}
func (a andFilter) Filter(line []byte) bool {
return a.left.Filter(line) && a.right.Filter(line)
}
func (a andFilter) ToStage() Stage {
return StageFunc{
process: func(_ int64, line []byte, _ *LabelsBuilder) ([]byte, bool) {
return line, a.Filter(line)
},
}
}
type andFilters struct {
filters []Filterer
}
// NewAndFilters creates a new filter which matches only if all filters match
func NewAndFilters(filters []Filterer) Filterer {
var containsFilterAcc *containsAllFilter
regexpFilters := make([]Filterer, 0)
n := 0
for _, filter := range filters {
// Make sure we take care of panics in case a nil or noop filter is passed.
if !(filter == nil || filter == TrueFilter) {
switch c := filter.(type) {
case *containsFilter:
// Start accumulating contains filters.
if containsFilterAcc == nil {
containsFilterAcc = &containsAllFilter{}
}
// Join all contain filters.
containsFilterAcc.Add(*c)
case regexpFilter:
regexpFilters = append(regexpFilters, c)
default:
// Finish accumulating contains filters.
if containsFilterAcc != nil {
filters[n] = containsFilterAcc
n++
containsFilterAcc = nil
}
// Keep filter
filters[n] = filter
n++
}
}
}
filters = filters[:n]
if containsFilterAcc != nil {
filters = append(filters, containsFilterAcc)
}
// Push regex filters to end
if len(regexpFilters) > 0 {
filters = append(filters, regexpFilters...)
}
if len(filters) == 0 {
return TrueFilter
} else if len(filters) == 1 {
return filters[0]
}
return andFilters{
filters: filters,
}
}
func (a andFilters) Filter(line []byte) bool {
for _, filter := range a.filters {
if !filter.Filter(line) {
return false
}
}
return true
}
func (a andFilters) ToStage() Stage {
return StageFunc{
process: func(_ int64, line []byte, _ *LabelsBuilder) ([]byte, bool) {
return line, a.Filter(line)
},
}
}
type orFilter struct {
left Filterer
right Filterer
}
// newOrFilter creates a new filter which matches only if left or right matches.
func newOrFilter(left Filterer, right Filterer) Filterer {
if left == nil || left == TrueFilter {
return right
}
if right == nil || right == TrueFilter {
return left
}
return orFilter{
left: left,
right: right,
}
}
// chainOrFilter is a syntax sugar to chain multiple `or` filters. (1 or many)
func chainOrFilter(curr, new Filterer) Filterer {
if curr == nil {
return new
}
return newOrFilter(curr, new)
}
func (a orFilter) Filter(line []byte) bool {
return a.left.Filter(line) || a.right.Filter(line)
}
func (a orFilter) ToStage() Stage {
return StageFunc{
process: func(_ int64, line []byte, _ *LabelsBuilder) ([]byte, bool) {
return line, a.Filter(line)
},
}
}
type regexpFilter struct {
*regexp.Regexp
orig string
}
// newRegexpFilter creates a new line filter for a given regexp.
// If match is false the filter is the negation of the regexp.
func newRegexpFilter(re string, orig string, match bool) (Filterer, error) {
reg, err := regexp.Compile(re)
if err != nil {
return nil, err
}
f := regexpFilter{Regexp: reg, orig: orig}
if match {
return f, nil
}
return newNotFilter(f), nil
}
func (r regexpFilter) Filter(line []byte) bool {
return r.Match(line)
}
func (r regexpFilter) ToStage() Stage {
return StageFunc{
process: func(_ int64, line []byte, _ *LabelsBuilder) ([]byte, bool) {
return line, r.Filter(line)
},
}
}
func (r regexpFilter) String() string {
return r.orig
}
type equalFilter struct {
match []byte
caseInsensitive bool
}
func (l equalFilter) Filter(line []byte) bool {
if len(l.match) != len(line) {
return false
}
return contains(line, l.match, l.caseInsensitive)
}
func (l equalFilter) ToStage() Stage {
return StageFunc{
process: func(_ int64, line []byte, _ *LabelsBuilder) ([]byte, bool) {
return line, l.Filter(line)
},
}
}
func (l equalFilter) String() string {
return string(l.match)
}
func newEqualFilter(match []byte, caseInsensitive bool) Filterer {
return equalFilter{match, caseInsensitive}
}
type containsFilter struct {
match []byte
caseInsensitive bool
}
func (l *containsFilter) Filter(line []byte) bool {
return contains(line, l.match, l.caseInsensitive)
}
func contains(line, substr []byte, caseInsensitive bool) bool {
if !caseInsensitive {
return bytes.Contains(line, substr)
}
return containsLower(line, substr)
}
func containsLower(line, substr []byte) bool {
if len(substr) == 0 {
return true
}
if len(substr) > len(line) {
return false
}
j := 0
for len(line) > 0 {
// ascii fast case
if c := line[0]; c < utf8.RuneSelf && substr[j] < utf8.RuneSelf {
if c == substr[j] || c+'a'-'A' == substr[j] || c == substr[j]+'a'-'A' {
j++
if j == len(substr) {
return true
}
line = line[1:]
continue
}
line = line[1:]
j = 0
continue
}
// unicode slow case
lr, lwid := utf8.DecodeRune(line)
mr, mwid := utf8.DecodeRune(substr[j:])
if lr == mr || mr == unicode.To(unicode.LowerCase, lr) {
j += mwid
if j == len(substr) {
return true
}
line = line[lwid:]
continue
}
line = line[lwid:]
j = 0
}
return false
}
func (l containsFilter) ToStage() Stage {
return StageFunc{
process: func(_ int64, line []byte, _ *LabelsBuilder) ([]byte, bool) {
return line, l.Filter(line)
},
}
}
func (l containsFilter) String() string {
return string(l.match)
}
// newContainsFilter creates a contains filter that checks if a log line contains a match.
func newContainsFilter(match []byte, caseInsensitive bool) Filterer {
if len(match) == 0 {
return TrueFilter
}
if caseInsensitive {
match = bytes.ToLower(match)
}
return &containsFilter{
match: match,
caseInsensitive: caseInsensitive,
}
}
type containsAllFilter struct {
matches []containsFilter
}
func (f *containsAllFilter) Add(filter containsFilter) {
f.matches = append(f.matches, filter)
}
func (f *containsAllFilter) Empty() bool {
return len(f.matches) == 0
}
func (f containsAllFilter) Filter(line []byte) bool {
for _, m := range f.matches {
if !contains(line, m.match, m.caseInsensitive) {
return false
}
}
return true
}
func (f containsAllFilter) ToStage() Stage {
return StageFunc{
process: func(_ int64, line []byte, _ *LabelsBuilder) ([]byte, bool) {
return line, f.Filter(line)
},
}
}
// NewFilter creates a new line filter from a match string and type.
func NewFilter(match string, mt labels.MatchType) (Filterer, error) {
switch mt {
case labels.MatchRegexp:
return parseRegexpFilter(match, true, false)
case labels.MatchNotRegexp:
return parseRegexpFilter(match, false, false)
case labels.MatchEqual:
return newContainsFilter([]byte(match), false), nil
case labels.MatchNotEqual:
return newNotFilter(newContainsFilter([]byte(match), false)), nil
default:
return nil, fmt.Errorf("unknown matcher: %v", match)
}
}
// NewLabelFilter creates a new filter that has label regex semantics
func NewLabelFilter(match string, mt labels.MatchType) (Filterer, error) {
switch mt {
case labels.MatchRegexp:
return parseRegexpFilter(match, true, true)
case labels.MatchNotRegexp:
return parseRegexpFilter(match, false, true)
case labels.MatchEqual:
return newEqualFilter([]byte(match), false), nil
case labels.MatchNotEqual:
return newNotFilter(newEqualFilter([]byte(match), false)), nil
default:
return nil, fmt.Errorf("unknown matcher: %v", match)
}
}
// parseRegexpFilter parses a regexp and attempt to simplify it with only literal filters.
// If not possible it will returns the original regexp filter.
func parseRegexpFilter(re string, match bool, isLabel bool) (Filterer, error) {
reg, err := syntax.Parse(re, syntax.Perl)
if err != nil {
return nil, err
}
reg = reg.Simplify()
// attempt to improve regex with tricks
f, ok := simplify(reg, isLabel)
if !ok {
util.AllNonGreedy(reg)
regex := reg.String()
if isLabel {
// label regexes are anchored to
// the beginning and ending of lines
regex = "^(?:" + regex + ")$"
}
return newRegexpFilter(regex, re, match)
}
if match {
return f, nil
}
return newNotFilter(f), nil
}
// simplify a regexp expression by replacing it, when possible, with a succession of literal filters.
// For example `(foo|bar)` will be replaced by `containsFilter(foo) or containsFilter(bar)`
func simplify(reg *syntax.Regexp, isLabel bool) (Filterer, bool) {
switch reg.Op {
case syntax.OpAlternate:
return simplifyAlternate(reg, isLabel)
case syntax.OpConcat:
return simplifyConcat(reg, nil)
case syntax.OpCapture:
util.ClearCapture(reg)
return simplify(reg, isLabel)
case syntax.OpLiteral:
if isLabel {
return newEqualFilter([]byte(string(reg.Rune)), util.IsCaseInsensitive(reg)), true
}
return newContainsFilter([]byte(string(reg.Rune)), util.IsCaseInsensitive(reg)), true
case syntax.OpStar:
if reg.Sub[0].Op == syntax.OpAnyCharNotNL {
return TrueFilter, true
}
case syntax.OpPlus:
if len(reg.Sub) == 1 && reg.Sub[0].Op == syntax.OpAnyCharNotNL { // simplify ".+"
return ExistsFilter, true
}
case syntax.OpEmptyMatch:
return TrueFilter, true
}
return nil, false
}
// simplifyAlternate simplifies, when possible, alternate regexp expressions such as:
// (foo|bar) or (foo|(bar|buzz)).
func simplifyAlternate(reg *syntax.Regexp, isLabel bool) (Filterer, bool) {
util.ClearCapture(reg.Sub...)
// attempt to simplify the first leg
f, ok := simplify(reg.Sub[0], isLabel)
if !ok {
return nil, false
}
// merge the rest of the legs
for i := 1; i < len(reg.Sub); i++ {
f2, ok := simplify(reg.Sub[i], isLabel)
if !ok {
return nil, false
}
f = newOrFilter(f, f2)
}
return f, true
}
// simplifyConcat attempt to simplify concat operations.
// Concat operations are either literal and star such as foo.* .*foo.* .*foo
// which is a literalFilter.
// Or a literal and alternates operation (see simplifyConcatAlternate), which represent a multiplication of alternates.
// Anything else is rejected.
func simplifyConcat(reg *syntax.Regexp, baseLiteral []byte) (Filterer, bool) {
util.ClearCapture(reg.Sub...)
// remove empty match as we don't need them for filtering
i := 0
for _, r := range reg.Sub {
if r.Op == syntax.OpEmptyMatch {
continue
}
reg.Sub[i] = r
i++
}
reg.Sub = reg.Sub[:i]
// we support only simplication of concat operation with 3 sub expressions.
// for instance .*foo.*bar contains 4 subs (.*+foo+.*+bar) and can't be simplified.
if len(reg.Sub) > 3 {
return nil, false
}
var curr Filterer
var ok bool
literals := 0
var baseLiteralIsCaseInsensitive bool
for _, sub := range reg.Sub {
if sub.Op == syntax.OpLiteral {
// only one literal is allowed.
if literals != 0 {
return nil, false
}
literals++
baseLiteral = append(baseLiteral, []byte(string(sub.Rune))...)
baseLiteralIsCaseInsensitive = util.IsCaseInsensitive(sub)
continue
}
// if we have an alternate we must also have a base literal to apply the concatenation with.
if sub.Op == syntax.OpAlternate && baseLiteral != nil {
if curr, ok = simplifyConcatAlternate(sub, baseLiteral, curr, baseLiteralIsCaseInsensitive); !ok {
return nil, false
}
continue
}
if sub.Op == syntax.OpStar && sub.Sub[0].Op == syntax.OpAnyCharNotNL {
continue
}
return nil, false
}
// if we have a filter from concat alternates.
if curr != nil {
return curr, true
}
// if we have only a concat with literals.
if baseLiteral != nil {
return newContainsFilter(baseLiteral, baseLiteralIsCaseInsensitive), true
}
return nil, false
}
// simplifyConcatAlternate simplifies concat alternate operations.
// A concat alternate is found when a concat operation has a sub alternate and is preceded by a literal.
// For instance bar|b|buzz is expressed as b(ar|(?:)|uzz) => b concat alternate(ar,(?:),uzz).
// (?:) being an OpEmptyMatch and b being the literal to concat all alternates (ar,(?:),uzz) with.
func simplifyConcatAlternate(reg *syntax.Regexp, literal []byte, curr Filterer, baseLiteralIsCaseInsensitive bool) (Filterer, bool) {
for _, alt := range reg.Sub {
// we should not consider the case where baseLiteral is not marked as case insensitive
// and alternate expression is marked as case insensitive. For example, for the original expression
// f|f(?i)oo the extracted expression would be "f (?:)|(?i:OO)" i.e. f with empty match
// and fOO. For fOO, we can't initialize containsFilter with caseInsensitve variable as either true or false
isAltCaseInsensitive := util.IsCaseInsensitive(alt)
if !baseLiteralIsCaseInsensitive && isAltCaseInsensitive {
return nil, false
}
switch alt.Op {
case syntax.OpEmptyMatch:
curr = chainOrFilter(curr, newContainsFilter(literal, baseLiteralIsCaseInsensitive))
case syntax.OpLiteral:
// concat the root literal with the alternate one.
altBytes := []byte(string(alt.Rune))
altLiteral := make([]byte, 0, len(literal)+len(altBytes))
altLiteral = append(altLiteral, literal...)
altLiteral = append(altLiteral, altBytes...)
curr = chainOrFilter(curr, newContainsFilter(altLiteral, baseLiteralIsCaseInsensitive))
case syntax.OpConcat:
f, ok := simplifyConcat(alt, literal)
if !ok {
return nil, false
}
curr = chainOrFilter(curr, f)
case syntax.OpStar:
if alt.Sub[0].Op != syntax.OpAnyCharNotNL {
return nil, false
}
curr = chainOrFilter(curr, newContainsFilter(literal, baseLiteralIsCaseInsensitive))
default:
return nil, false
}
}
if curr != nil {
return curr, true
}
return nil, false
}