func()

in transaction.go [44:173]
109 lines of code
21 McCabe index (conditional complexity)

func (t *Tracer) StartTransactionOptions(name, transactionType string, opts TransactionOptions) *Transaction {
	td, _ := t.transactionDataPool.Get().(*TransactionData)
	if td == nil {
		td = &TransactionData{
			Duration: -1,
			Context: Context{
				captureBodyMask: CaptureBodyTransactions,
			},
			spanTimings:       make(spanTimingsMap),
			droppedSpansStats: make(droppedSpanTimingsMap),
		}
		var seed int64
		if err := binary.Read(cryptorand.Reader, binary.LittleEndian, &seed); err != nil {
			seed = time.Now().UnixNano()
		}
		td.rand = rand.New(rand.NewSource(seed))
	}
	tx := &Transaction{tracer: t, TransactionData: td}

	// Take a snapshot of config that should apply to all spans within the
	// transaction.
	instrumentationConfig := t.instrumentationConfig()
	tx.recording = instrumentationConfig.recording
	if !tx.recording || !t.Active() {
		return tx
	}

	tx.maxSpans = instrumentationConfig.maxSpans
	tx.compressedSpan.options = instrumentationConfig.compressionOptions
	tx.exitSpanMinDuration = instrumentationConfig.exitSpanMinDuration
	tx.spanStackTraceMinDuration = instrumentationConfig.spanStackTraceMinDuration
	tx.stackTraceLimit = instrumentationConfig.stackTraceLimit
	tx.Context.captureHeaders = instrumentationConfig.captureHeaders
	tx.propagateLegacyHeader = instrumentationConfig.propagateLegacyHeader
	tx.Context.sanitizedFieldNames = instrumentationConfig.sanitizedFieldNames
	tx.breakdownMetricsEnabled = t.breakdownMetrics.enabled

	continuationStrategy := instrumentationConfig.continuationStrategy
	shouldRestartTrace := false
	if continuationStrategy == "restart_external" {
		if opts.TraceContext.State.haveElastic {
			continuationStrategy = "continue"
		} else {
			continuationStrategy = "restart"
		}
	}

	if continuationStrategy == "restart" {
		if !opts.TraceContext.Trace.isZero() && !opts.TraceContext.Span.isZero() {
			link := SpanLink{
				Trace: opts.TraceContext.Trace,
				Span:  opts.TraceContext.Span,
			}
			tx.links = append(tx.links, link)
			shouldRestartTrace = true
		}
	}

	var root bool
	if opts.TraceContext.Trace.Validate() == nil && !shouldRestartTrace {
		tx.traceContext.Trace = opts.TraceContext.Trace
		tx.traceContext.Options = opts.TraceContext.Options
		if opts.TraceContext.Span.Validate() == nil {
			tx.parentID = opts.TraceContext.Span
		}
		if opts.TransactionID.Validate() == nil {
			tx.traceContext.Span = opts.TransactionID
		} else {
			binary.LittleEndian.PutUint64(tx.traceContext.Span[:], tx.rand.Uint64())
		}
		if opts.TraceContext.State.Validate() == nil {
			tx.traceContext.State = opts.TraceContext.State
		}
	} else {
		// Start a new trace. We reuse the trace ID for the root transaction's ID
		// if one is not specified in the options.
		root = true
		binary.LittleEndian.PutUint64(tx.traceContext.Trace[:8], tx.rand.Uint64())
		binary.LittleEndian.PutUint64(tx.traceContext.Trace[8:], tx.rand.Uint64())
		if opts.TransactionID.Validate() == nil {
			tx.traceContext.Span = opts.TransactionID
		} else {
			copy(tx.traceContext.Span[:], tx.traceContext.Trace[:])
		}
	}

	if root {
		var result SampleResult
		if instrumentationConfig.sampler != nil {
			result = instrumentationConfig.sampler.Sample(SampleParams{
				TraceContext: tx.traceContext,
			})
			if !result.Sampled {
				// Special case: for unsampled transactions we
				// report a sample rate of 0, so that we do not
				// count them in aggregations in the server.
				// This is necessary to avoid overcounting, as
				// we will scale the sampled transactions.
				result.SampleRate = 0
			}
			sampleRate := roundSampleRate(result.SampleRate)
			tx.traceContext.State = NewTraceState(TraceStateEntry{
				Key:   elasticTracestateVendorKey,
				Value: formatElasticTracestateValue(sampleRate),
			})
		} else {
			result.Sampled = true
		}
		if result.Sampled {
			o := tx.traceContext.Options.WithRecorded(true)
			tx.traceContext.Options = o
		}
	} else {
		// TODO(axw) make this behaviour configurable. In some cases
		// it may not be a good idea to honour the recorded flag, as
		// it may open up the application to DoS by forced sampling.
		// Even ignoring bad actors, a service that has many feeder
		// applications may end up being sampled at a very high rate.
		tx.traceContext.Options = opts.TraceContext.Options
	}

	tx.Name = name
	tx.Type = transactionType
	tx.timestamp = opts.Start
	if tx.timestamp.IsZero() {
		tx.timestamp = time.Now()
	}
	tx.links = append(tx.links, opts.Links...)
	return tx
}