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// 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
}
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