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/transport_udp.go

@@ -0,0 +1,131 @@
+// 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 jaeger
+
+import (
+	"errors"
+	"fmt"
+
+	"github.com/uber/jaeger-client-go/thrift"
+
+	j "github.com/uber/jaeger-client-go/thrift-gen/jaeger"
+	"github.com/uber/jaeger-client-go/utils"
+)
+
+// Empirically obtained constant for how many bytes in the message are used for envelope.
+// The total datagram size is:
+// sizeof(Span) * numSpans + processByteSize + emitBatchOverhead <= maxPacketSize
+// There is a unit test `TestEmitBatchOverhead` that validates this number.
+// Note that due to the use of Compact Thrift protocol, overhead grows with the number of spans
+// in the batch, because the length of the list is encoded as varint32, as well as SeqId.
+const emitBatchOverhead = 30
+
+var errSpanTooLarge = errors.New("Span is too large")
+
+type udpSender struct {
+	client          *utils.AgentClientUDP
+	maxPacketSize   int                   // max size of datagram in bytes
+	maxSpanBytes    int                   // max number of bytes to record spans (excluding envelope) in the datagram
+	byteBufferSize  int                   // current number of span bytes accumulated in the buffer
+	spanBuffer      []*j.Span             // spans buffered before a flush
+	thriftBuffer    *thrift.TMemoryBuffer // buffer used to calculate byte size of a span
+	thriftProtocol  thrift.TProtocol
+	process         *j.Process
+	processByteSize int
+}
+
+// NewUDPTransport creates a reporter that submits spans to jaeger-agent
+func NewUDPTransport(hostPort string, maxPacketSize int) (Transport, error) {
+	if len(hostPort) == 0 {
+		hostPort = fmt.Sprintf("%s:%d", DefaultUDPSpanServerHost, DefaultUDPSpanServerPort)
+	}
+	if maxPacketSize == 0 {
+		maxPacketSize = utils.UDPPacketMaxLength
+	}
+
+	protocolFactory := thrift.NewTCompactProtocolFactory()
+
+	// Each span is first written to thriftBuffer to determine its size in bytes.
+	thriftBuffer := thrift.NewTMemoryBufferLen(maxPacketSize)
+	thriftProtocol := protocolFactory.GetProtocol(thriftBuffer)
+
+	client, err := utils.NewAgentClientUDP(hostPort, maxPacketSize)
+	if err != nil {
+		return nil, err
+	}
+
+	sender := &udpSender{
+		client:         client,
+		maxSpanBytes:   maxPacketSize - emitBatchOverhead,
+		thriftBuffer:   thriftBuffer,
+		thriftProtocol: thriftProtocol}
+	return sender, nil
+}
+
+func (s *udpSender) calcSizeOfSerializedThrift(thriftStruct thrift.TStruct) int {
+	s.thriftBuffer.Reset()
+	thriftStruct.Write(s.thriftProtocol)
+	return s.thriftBuffer.Len()
+}
+
+func (s *udpSender) Append(span *Span) (int, error) {
+	if s.process == nil {
+		s.process = BuildJaegerProcessThrift(span)
+		s.processByteSize = s.calcSizeOfSerializedThrift(s.process)
+		s.byteBufferSize += s.processByteSize
+	}
+	jSpan := BuildJaegerThrift(span)
+	spanSize := s.calcSizeOfSerializedThrift(jSpan)
+	if spanSize > s.maxSpanBytes {
+		return 1, errSpanTooLarge
+	}
+
+	s.byteBufferSize += spanSize
+	if s.byteBufferSize <= s.maxSpanBytes {
+		s.spanBuffer = append(s.spanBuffer, jSpan)
+		if s.byteBufferSize < s.maxSpanBytes {
+			return 0, nil
+		}
+		return s.Flush()
+	}
+	// the latest span did not fit in the buffer
+	n, err := s.Flush()
+	s.spanBuffer = append(s.spanBuffer, jSpan)
+	s.byteBufferSize = spanSize + s.processByteSize
+	return n, err
+}
+
+func (s *udpSender) Flush() (int, error) {
+	n := len(s.spanBuffer)
+	if n == 0 {
+		return 0, nil
+	}
+	err := s.client.EmitBatch(&j.Batch{Process: s.process, Spans: s.spanBuffer})
+	s.resetBuffers()
+
+	return n, err
+}
+
+func (s *udpSender) Close() error {
+	return s.client.Close()
+}
+
+func (s *udpSender) resetBuffers() {
+	for i := range s.spanBuffer {
+		s.spanBuffer[i] = nil
+	}
+	s.spanBuffer = s.spanBuffer[:0]
+	s.byteBufferSize = s.processByteSize
+}