65 lines
1.8 KiB
Go
65 lines
1.8 KiB
Go
package tracing
|
|
|
|
import (
|
|
"crypto/sha256"
|
|
"fmt"
|
|
"strings"
|
|
|
|
"github.com/containous/traefik/pkg/log"
|
|
)
|
|
|
|
// TraceNameHashLength defines the number of characters to use from the head of the generated hash.
|
|
const TraceNameHashLength = 8
|
|
|
|
// OperationNameMaxLengthNumber defines the number of static characters in a Span Trace name:
|
|
// 8 chars for hash + 2 chars for '_'.
|
|
const OperationNameMaxLengthNumber = 10
|
|
|
|
func generateOperationName(prefix string, parts []string, sep string, spanLimit int) string {
|
|
name := prefix + " " + strings.Join(parts, sep)
|
|
|
|
maxLength := OperationNameMaxLengthNumber + len(prefix) + 1
|
|
|
|
if spanLimit > 0 && len(name) > spanLimit {
|
|
if spanLimit < maxLength {
|
|
log.WithoutContext().Warnf("SpanNameLimit cannot be lesser than %d: falling back on %d, maxLength, maxLength+3", maxLength)
|
|
spanLimit = maxLength + 3
|
|
}
|
|
|
|
limit := (spanLimit - maxLength) / 2
|
|
|
|
var fragments []string
|
|
for _, value := range parts {
|
|
fragments = append(fragments, truncateString(value, limit))
|
|
}
|
|
fragments = append(fragments, computeHash(name))
|
|
|
|
name = prefix + " " + strings.Join(fragments, sep)
|
|
}
|
|
|
|
return name
|
|
}
|
|
|
|
// truncateString reduces the length of the 'str' argument to 'num' - 3 and adds a '...' suffix to the tail.
|
|
func truncateString(str string, num int) string {
|
|
text := str
|
|
if len(str) > num {
|
|
if num > 3 {
|
|
num -= 3
|
|
}
|
|
text = str[0:num] + "..."
|
|
}
|
|
return text
|
|
}
|
|
|
|
// computeHash returns the first TraceNameHashLength character of the sha256 hash for 'name' argument.
|
|
func computeHash(name string) string {
|
|
data := []byte(name)
|
|
hash := sha256.New()
|
|
if _, err := hash.Write(data); err != nil {
|
|
// Impossible case
|
|
log.WithoutContext().WithField("OperationName", name).Errorf("Failed to create Span name hash for %s: %v", name, err)
|
|
}
|
|
|
|
return fmt.Sprintf("%x", hash.Sum(nil))[:TraceNameHashLength]
|
|
}
|