138 lines
4.6 KiB
Go
138 lines
4.6 KiB
Go
// Copyright (c) 2016 Uber Technologies, Inc.
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in
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// all copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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// THE SOFTWARE.
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package jaeger
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import (
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"errors"
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"github.com/apache/thrift/lib/go/thrift"
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j "github.com/uber/jaeger-client-go/thrift-gen/jaeger"
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"github.com/uber/jaeger-client-go/utils"
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)
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// Empirically obtained constant for how many bytes in the message are used for envelope.
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// The total datagram size is:
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// sizeof(Span) * numSpans + processByteSize + emitBatchOverhead <= maxPacketSize
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// There is a unit test `TestEmitBatchOverhead` that validates this number.
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// Note that due to the use of Compact Thrift protocol, overhead grows with the number of spans
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// in the batch, because the length of the list is encoded as varint32, as well as SeqId.
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const emitBatchOverhead = 30
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const defaultUDPSpanServerHostPort = "localhost:6831"
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var errSpanTooLarge = errors.New("Span is too large")
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type udpSender struct {
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client *utils.AgentClientUDP
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maxPacketSize int // max size of datagram in bytes
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maxSpanBytes int // max number of bytes to record spans (excluding envelope) in the datagram
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byteBufferSize int // current number of span bytes accumulated in the buffer
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spanBuffer []*j.Span // spans buffered before a flush
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thriftBuffer *thrift.TMemoryBuffer // buffer used to calculate byte size of a span
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thriftProtocol thrift.TProtocol
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process *j.Process
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processByteSize int
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}
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// NewUDPTransport creates a reporter that submits spans to jaeger-agent
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func NewUDPTransport(hostPort string, maxPacketSize int) (Transport, error) {
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if len(hostPort) == 0 {
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hostPort = defaultUDPSpanServerHostPort
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}
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if maxPacketSize == 0 {
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maxPacketSize = utils.UDPPacketMaxLength
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}
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protocolFactory := thrift.NewTCompactProtocolFactory()
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// Each span is first written to thriftBuffer to determine its size in bytes.
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thriftBuffer := thrift.NewTMemoryBufferLen(maxPacketSize)
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thriftProtocol := protocolFactory.GetProtocol(thriftBuffer)
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client, err := utils.NewAgentClientUDP(hostPort, maxPacketSize)
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if err != nil {
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return nil, err
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}
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sender := &udpSender{
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client: client,
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maxSpanBytes: maxPacketSize - emitBatchOverhead,
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thriftBuffer: thriftBuffer,
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thriftProtocol: thriftProtocol}
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return sender, nil
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}
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func (s *udpSender) calcSizeOfSerializedThrift(thriftStruct thrift.TStruct) int {
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s.thriftBuffer.Reset()
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thriftStruct.Write(s.thriftProtocol)
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return s.thriftBuffer.Len()
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}
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func (s *udpSender) Append(span *Span) (int, error) {
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if s.process == nil {
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s.process = BuildJaegerProcessThrift(span)
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s.processByteSize = s.calcSizeOfSerializedThrift(s.process)
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s.byteBufferSize += s.processByteSize
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}
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jSpan := BuildJaegerThrift(span)
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spanSize := s.calcSizeOfSerializedThrift(jSpan)
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if spanSize > s.maxSpanBytes {
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return 1, errSpanTooLarge
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}
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s.byteBufferSize += spanSize
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if s.byteBufferSize <= s.maxSpanBytes {
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s.spanBuffer = append(s.spanBuffer, jSpan)
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if s.byteBufferSize < s.maxSpanBytes {
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return 0, nil
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}
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return s.Flush()
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}
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// the latest span did not fit in the buffer
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n, err := s.Flush()
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s.spanBuffer = append(s.spanBuffer, jSpan)
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s.byteBufferSize = spanSize + s.processByteSize
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return n, err
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}
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func (s *udpSender) Flush() (int, error) {
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n := len(s.spanBuffer)
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if n == 0 {
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return 0, nil
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}
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err := s.client.EmitBatch(&j.Batch{Process: s.process, Spans: s.spanBuffer})
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s.resetBuffers()
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return n, err
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}
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func (s *udpSender) Close() error {
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return s.client.Close()
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}
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func (s *udpSender) resetBuffers() {
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for i := range s.spanBuffer {
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s.spanBuffer[i] = nil
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}
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s.spanBuffer = s.spanBuffer[:0]
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s.byteBufferSize = s.processByteSize
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}
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