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perf: reduce allocations in (*routeRegexp).getURLQuery (#544)
A production server is seeing a significant amount of allocations in (*routeRegexp).getURLQuery

Since it is only interested in a single value and only the first value we create a specialized function for that.

Comparing a few parameter parsing scenarios:

```
Benchmark_findQueryKey/0-8 	 7184014	       168 ns/op	       0 B/op	       0 allocs/op
Benchmark_findQueryKey/1-8 	 5307873	       227 ns/op	      48 B/op	       3 allocs/op
Benchmark_findQueryKey/2-8 	 1560836	       770 ns/op	     483 B/op	      10 allocs/op
Benchmark_findQueryKey/3-8 	 1296200	       931 ns/op	     559 B/op	      11 allocs/op
Benchmark_findQueryKey/4-8 	  666502	      1769 ns/op	       3 B/op	       1 allocs/op

Benchmark_findQueryKeyGoLib/0-8 	 1740973	       690 ns/op	     864 B/op	       8 allocs/op
Benchmark_findQueryKeyGoLib/1-8 	 3029618	       393 ns/op	     432 B/op	       4 allocs/op
Benchmark_findQueryKeyGoLib/2-8 	  461427	      2511 ns/op	    1542 B/op	      24 allocs/op
Benchmark_findQueryKeyGoLib/3-8 	  324252	      3804 ns/op	    1984 B/op	      28 allocs/op
Benchmark_findQueryKeyGoLib/4-8 	   69348	     14928 ns/op	   12716 B/op	     130 allocs/op
```
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klauspost authored and elithrar committed Jan 12, 2020
1 parent 49c0148 commit 75dcda0896e109a2a22c9315bca3bb21b87b2ba5
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Showing 2 changed files with 132 additions and 4 deletions.
@@ -230,14 +230,51 @@ func (r *routeRegexp) getURLQuery(req *http.Request) string {
return ""
}
templateKey := strings.SplitN(r.template, "=", 2)[0]
for key, vals := range req.URL.Query() {
if key == templateKey && len(vals) > 0 {
return key + "=" + vals[0]
}
val, ok := findFirstQueryKey(req.URL.RawQuery, templateKey)
if ok {
return templateKey + "=" + val
}
return ""
}

// findFirstQueryKey returns the same result as (*url.URL).Query()[key][0].
// If key was not found, empty string and false is returned.
func findFirstQueryKey(rawQuery, key string) (value string, ok bool) {
query := []byte(rawQuery)
for len(query) > 0 {
foundKey := query
if i := bytes.IndexAny(foundKey, "&;"); i >= 0 {
foundKey, query = foundKey[:i], foundKey[i+1:]
} else {
query = query[:0]
}
if len(foundKey) == 0 {
continue
}
var value []byte
if i := bytes.IndexByte(foundKey, '='); i >= 0 {
foundKey, value = foundKey[:i], foundKey[i+1:]
}
if len(foundKey) < len(key) {
// Cannot possibly be key.
continue
}
keyString, err := url.QueryUnescape(string(foundKey))
if err != nil {
continue
}
if keyString != key {
continue
}
valueString, err := url.QueryUnescape(string(value))
if err != nil {
continue
}
return valueString, true
}
return "", false
}

func (r *routeRegexp) matchQueryString(req *http.Request) bool {
return r.regexp.MatchString(r.getURLQuery(req))
}
@@ -0,0 +1,91 @@
package mux

import (
"net/url"
"reflect"
"strconv"
"testing"
)

func Test_findFirstQueryKey(t *testing.T) {
tests := []string{
"a=1&b=2",
"a=1&a=2&a=banana",
"ascii=%3Ckey%3A+0x90%3E",
"a=1;b=2",
"a=1&a=2;a=banana",
"a==",
"a=%2",
"a=20&%20%3F&=%23+%25%21%3C%3E%23%22%7B%7D%7C%5C%5E%5B%5D%60%E2%98%BA%09:%2F@$%27%28%29%2A%2C%3B&a=30",
"a=1& ?&=#+%!<>#\"{}|\\^[]`鈽\t:/@$'()*,;&a=5",
"a=xxxxxxxxxxxxxxxx&b=YYYYYYYYYYYYYYY&c=ppppppppppppppppppp&f=ttttttttttttttttt&a=uuuuuuuuuuuuu",
}
for _, query := range tests {
t.Run(query, func(t *testing.T) {
// Check against url.ParseQuery, ignoring the error.
all, _ := url.ParseQuery(query)
for key, want := range all {
t.Run(key, func(t *testing.T) {
got, ok := findFirstQueryKey(query, key)
if !ok {
t.Error("Did not get expected key", key)
}
if !reflect.DeepEqual(got, want[0]) {
t.Errorf("findFirstQueryKey(%s,%s) = %v, want %v", query, key, got, want[0])
}
})
}
})
}
}

func Benchmark_findQueryKey(b *testing.B) {
tests := []string{
"a=1&b=2",
"ascii=%3Ckey%3A+0x90%3E",
"a=20&%20%3F&=%23+%25%21%3C%3E%23%22%7B%7D%7C%5C%5E%5B%5D%60%E2%98%BA%09:%2F@$%27%28%29%2A%2C%3B&a=30",
"a=xxxxxxxxxxxxxxxx&bbb=YYYYYYYYYYYYYYY&cccc=ppppppppppppppppppp&ddddd=ttttttttttttttttt&a=uuuuuuuuuuuuu",
"a=;b=;c=;d=;e=;f=;g=;h=;i=,j=;k=",
}
for i, query := range tests {
b.Run(strconv.Itoa(i), func(b *testing.B) {
// Check against url.ParseQuery, ignoring the error.
all, _ := url.ParseQuery(query)
b.ReportAllocs()
b.ResetTimer()
for i := 0; i < b.N; i++ {
for key, _ := range all {
_, _ = findFirstQueryKey(query, key)
}
}
})
}
}

func Benchmark_findQueryKeyGoLib(b *testing.B) {
tests := []string{
"a=1&b=2",
"ascii=%3Ckey%3A+0x90%3E",
"a=20&%20%3F&=%23+%25%21%3C%3E%23%22%7B%7D%7C%5C%5E%5B%5D%60%E2%98%BA%09:%2F@$%27%28%29%2A%2C%3B&a=30",
"a=xxxxxxxxxxxxxxxx&bbb=YYYYYYYYYYYYYYY&cccc=ppppppppppppppppppp&ddddd=ttttttttttttttttt&a=uuuuuuuuuuuuu",
"a=;b=;c=;d=;e=;f=;g=;h=;i=,j=;k=",
}
for i, query := range tests {
b.Run(strconv.Itoa(i), func(b *testing.B) {
// Check against url.ParseQuery, ignoring the error.
all, _ := url.ParseQuery(query)
var u url.URL
u.RawQuery = query
b.ReportAllocs()
b.ResetTimer()
for i := 0; i < b.N; i++ {
for key, _ := range all {
v := u.Query()[key]
if len(v) > 0 {
_ = v[0]
}
}
}
})
}
}

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