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parse.go
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parse.go
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package route
import (
"bufio"
"fmt"
"io"
"os"
"regexp"
"strconv"
"strings"
)
// Parse loads a routing table from a set of route commands.
//
// The commands are parsed in order and order matters.
// Deleting a route that has not been created yet yields
// a different result than the other way around.
//
// Route commands can have the following form:
//
// route add <svc> <src> <dst> weight <w> tags "<t1>,<t2>,..."
// - Add route for service svc from src to dst and assign weight and tags
//
// route add <svc> <src> <dst> weight <w>
// - Add route for service svc from src to dst and assign weight
//
// route add <svc> <src> <dst> tags "<t1>,<t2>,..."
// - Add route for service svc from src to dst and assign tags
//
// route add <svc> <src> <dst>
// - Add route for service svc from src to dst
//
// route del <svc> <src> <dst>
// - Remove route matching svc, src and dst
//
// route del <svc> <src>
// - Remove all routes of services matching svc and src
//
// route del <svc>
// - Remove all routes of service matching svc
//
// route weight <svc> <src> weight <w> tags "<t1>,<t2>,..."
// - Route w% of traffic to all services matching svc, src and tags
//
// route weight <src> weight <w> tags "<t1>,<t2>,..."
// - Route w% of traffic to all services matching src and tags
//
// route weight <svc> <src> weight <w>
// - Route w% of traffic to all services matching svc and src
//
// route weight service host/path weight w tags "tag1,tag2"
// - Route w% of traffic to all services matching service, host/path and tags
//
// w is a float > 0 describing a percentage, e.g. 0.5 == 50%
// w <= 0: means no fixed weighting. Traffic is evenly distributed
// w > 0: route will receive n% of traffic. If sum(w) > 1 then w is normalized.
// sum(w) >= 1: only matching services will receive traffic
//
// Note that the total sum of traffic sent to all matching routes is w%.
//
func Parse(r io.Reader) (Table, error) {
p := &parser{t: make(Table)}
if err := p.parse(r); err != nil {
return nil, err
}
return p.t, nil
}
// ParseFile loads a routing table from a file.
func ParseFile(path string) (Table, error) {
f, err := os.Open(path)
if err != nil {
return nil, err
}
defer f.Close()
return Parse(f)
}
// ParseString loads a routing table from a string.
func ParseString(s string) (Table, error) {
return Parse(strings.NewReader(s))
}
type parser struct {
t Table
lineNumber int
line string
}
func (p *parser) parse(r io.Reader) error {
cmds := map[string]func(s string) error{
"route add ": p.routeAdd,
"route del ": p.routeDel,
"route weight ": p.routeWeight,
}
sc := bufio.NewScanner(r)
for sc.Scan() {
p.lineNumber++
p.line = strings.TrimSpace(sc.Text())
if p.line == "" || strings.HasPrefix(p.line, "#") {
continue
}
for cmd, fn := range cmds {
if !strings.HasPrefix(p.line, cmd) {
continue
}
if err := fn(p.line); err != nil {
return err
}
break
}
}
return nil
}
var (
// route add <svc> <src> <dst> weight <w> tags "<t1>,<t2>,..."
routeAddSvcWeightTags = regexp.MustCompile(`^route add (\S+) (\S+) (\S+) weight (\S+) tags "([^"]*)"$`)
// route add <svc> <src> <dst> weight <w>
routeAddSvcWeight = regexp.MustCompile(`^route add (\S+) (\S+) (\S+) weight (\S+)$`)
// route add <svc> <src> <dst> tags "<t1>,<t2>,..."
routeAddSvcTags = regexp.MustCompile(`^route add (\S+) (\S+) (\S+) tags "([^"]*)"$`)
// route add <svc> <src> <dst>
routeAddSvc = regexp.MustCompile(`^route add (\S+) (\S+) (\S+)$`)
)
func (p *parser) routeAdd(s string) error {
var svc, src, dst string
var tags []string
var w float64
var err error
// test most to least specific
if m := routeAddSvcWeightTags.FindStringSubmatch(s); m != nil {
svc, src, dst, tags = m[1], m[2], m[4], strings.Split(m[5], ",")
w, err = p.parseWeight(m[3])
} else if m := routeAddSvcWeight.FindStringSubmatch(s); m != nil {
svc, src, dst = m[1], m[2], m[3]
w, err = p.parseWeight(m[4])
} else if m := routeAddSvcTags.FindStringSubmatch(s); m != nil {
svc, src, dst, tags = m[1], m[2], m[3], strings.Split(m[4], ",")
} else if m := routeAddSvc.FindStringSubmatch(s); m != nil {
svc, src, dst = m[1], m[2], m[3]
} else {
err = p.syntaxError()
}
if err != nil {
return err
}
p.t.AddRoute(svc, src, dst, w, tags)
return nil
}
var (
// route del <svc> <src> <dst>
routeDelSvcSrcDst = regexp.MustCompile(`^route del (\S+) (\S+) (\S+)$`)
// route del <svc> <src>
routeDelSvcSrc = regexp.MustCompile(`^route del (\S+) (\S+)$`)
// route del <svc>
routeDelSvc = regexp.MustCompile(`^route del (\S+)$`)
)
func (p *parser) routeDel(s string) error {
var svc, src, dst string
var err error
// test most to least specific
if m := routeDelSvcSrcDst.FindStringSubmatch(s); m != nil {
svc, src, dst = m[1], m[2], m[3]
} else if m := routeDelSvcSrc.FindStringSubmatch(s); m != nil {
svc, src = m[1], m[2]
} else if m := routeDelSvc.FindStringSubmatch(s); m != nil {
svc = m[1]
} else {
err = p.syntaxError()
}
if err != nil {
return err
}
p.t.DelRoute(svc, src, dst)
return nil
}
var (
// route weight <svc> <src> weight <w> tags "<t1>,<t2>,..."'
routeWeightSvcSrcTags = regexp.MustCompile(`^route weight (\S+) (\S+) weight (\S+) tags "([^"]*)"$`)
// route weight <src> weight <w> tags "<t1>,<t2>,..."'
routeWeightSrcTags = regexp.MustCompile(`^route weight (\S+) weight (\S+) tags "([^"]+)"$`)
// route weight <svc> <src> weight <w>'
routeWeightSvcSrc = regexp.MustCompile(`^route weight (\S+) (\S+) weight (\S+)$`)
)
func (p *parser) routeWeight(s string) error {
var svc, src string
var tags []string
var w float64
var err error
// test most to least specific
if m := routeWeightSvcSrcTags.FindStringSubmatch(s); m != nil {
svc, src, tags = m[1], m[2], strings.Split(m[4], ",")
w, err = p.parseWeight(m[3])
} else if m := routeWeightSvcSrc.FindStringSubmatch(s); m != nil {
svc, src = m[1], m[2]
w, err = p.parseWeight(m[3])
} else if m := routeWeightSrcTags.FindStringSubmatch(s); m != nil {
src, tags = m[1], strings.Split(m[3], ",")
w, err = p.parseWeight(m[2])
} else {
err = p.syntaxError()
}
if err != nil {
return err
}
p.t.AddRouteWeight(svc, src, w, tags)
return nil
}
func (p *parser) parseWeight(s string) (float64, error) {
n, err := strconv.ParseFloat(s, 64)
if err != nil {
return 0, p.errorf("invalid weight: %s", s)
}
return n, nil
}
func (p *parser) syntaxError() error {
return fmt.Errorf("route: line %d: syntax error in %s", p.lineNumber, p.line)
}
func (p *parser) errorf(msg string, args ...string) error {
return fmt.Errorf("route: line %d: %s", p.lineNumber, fmt.Sprintf(msg, args))
}