swarm: integrate OpenTracing; propagate ctx to internal APIs (#17169)

* swarm: propagate ctx, enable opentracing

* swarm/tracing: log error when tracing is misconfigured

vendor/github.com/uber/jaeger-client-go/rpcmetrics/normalizer.go

@@ -0,0 +1,101 @@
+// Copyright (c) 2017 Uber Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package rpcmetrics
+
+// NameNormalizer is used to convert the endpoint names to strings
+// that can be safely used as tags in the metrics.
+type NameNormalizer interface {
+	Normalize(name string) string
+}
+
+// DefaultNameNormalizer converts endpoint names so that they contain only characters
+// from the safe charset [a-zA-Z0-9-./_]. All other characters are replaced with '-'.
+var DefaultNameNormalizer = &SimpleNameNormalizer{
+	SafeSets: []SafeCharacterSet{
+		&Range{From: 'a', To: 'z'},
+		&Range{From: 'A', To: 'Z'},
+		&Range{From: '0', To: '9'},
+		&Char{'-'},
+		&Char{'_'},
+		&Char{'/'},
+		&Char{'.'},
+	},
+	Replacement: '-',
+}
+
+// SimpleNameNormalizer uses a set of safe character sets.
+type SimpleNameNormalizer struct {
+	SafeSets    []SafeCharacterSet
+	Replacement byte
+}
+
+// SafeCharacterSet determines if the given character is "safe"
+type SafeCharacterSet interface {
+	IsSafe(c byte) bool
+}
+
+// Range implements SafeCharacterSet
+type Range struct {
+	From, To byte
+}
+
+// IsSafe implements SafeCharacterSet
+func (r *Range) IsSafe(c byte) bool {
+	return c >= r.From && c <= r.To
+}
+
+// Char implements SafeCharacterSet
+type Char struct {
+	Val byte
+}
+
+// IsSafe implements SafeCharacterSet
+func (ch *Char) IsSafe(c byte) bool {
+	return c == ch.Val
+}
+
+// Normalize checks each character in the string against SafeSets,
+// and if it's not safe substitutes it with Replacement.
+func (n *SimpleNameNormalizer) Normalize(name string) string {
+	var retMe []byte
+	nameBytes := []byte(name)
+	for i, b := range nameBytes {
+		if n.safeByte(b) {
+			if retMe != nil {
+				retMe[i] = b
+			}
+		} else {
+			if retMe == nil {
+				retMe = make([]byte, len(nameBytes))
+				copy(retMe[0:i], nameBytes[0:i])
+			}
+			retMe[i] = n.Replacement
+		}
+	}
+	if retMe == nil {
+		return name
+	}
+	return string(retMe)
+}
+
+// safeByte checks if b against all safe charsets.
+func (n *SimpleNameNormalizer) safeByte(b byte) bool {
+	for i := range n.SafeSets {
+		if n.SafeSets[i].IsSafe(b) {
+			return true
+		}
+	}
+	return false
+}