Add a flag for firehose mode (jaegertracing#419)

* Add a flag for firehose mode

Add 0b100 as a constant for Firehose mode and allow setting and checking
this on the span context.

fixes jaegertracing#417
ref #1731

Signed-off-by: Prithvi Raj <p.r@uber.com>

context.go

@@ -22,8 +22,9 @@ import (
 )
 
 const (
-	flagSampled = byte(1)
-	flagDebug   = byte(2)
+	flagSampled  = byte(1)
+	flagDebug    = byte(2)
+	flagFirehose = byte(8)
 )
 
 var (
@@ -88,6 +89,11 @@ func (c SpanContext) IsDebug() bool {
 	return (c.flags & flagDebug) == flagDebug
 }
 
+// IsFirehose indicates whether the firehose flag was set
+func (c SpanContext) IsFirehose() bool {
+	return (c.flags & flagFirehose) == flagFirehose
+}
+
 // IsValid indicates whether this context actually represents a valid trace.
 func (c SpanContext) IsValid() bool {
 	return c.traceID.IsValid() && c.spanID != 0

context_test.go

@@ -78,21 +78,79 @@ func TestSpanContext_WithBaggageItem(t *testing.T) {
 	assert.Equal(t, map[string]string{"some-KEY": "Some-Other-Value"}, ctx.baggage)
 }
 
-func TestSpanContext_SampledDebug(t *testing.T) {
-	ctx, err := ContextFromString("1:1:1:1")
-	require.NoError(t, err)
-	assert.True(t, ctx.IsSampled())
-	assert.False(t, ctx.IsDebug())
+func TestSpanContext_Flags(t *testing.T) {
 
-	ctx, err = ContextFromString("1:1:1:3")
-	require.NoError(t, err)
-	assert.True(t, ctx.IsSampled())
-	assert.True(t, ctx.IsDebug())
+	var tests = map[string]struct {
+		in           string
+		sampledFlag  bool
+		debugFlag    bool
+		firehoseFlag bool
+	}{
+		"None": {
+			in:           "1:1:1:0",
+			sampledFlag:  false,
+			debugFlag:    false,
+			firehoseFlag: false,
+		},
+		"Sampled Only": {
+			in:           "1:1:1:1",
+			sampledFlag:  true,
+			debugFlag:    false,
+			firehoseFlag: false,
+		},
 
-	ctx, err = ContextFromString("1:1:1:0")
-	require.NoError(t, err)
-	assert.False(t, ctx.IsSampled())
-	assert.False(t, ctx.IsDebug())
+		"Debug Only": {
+			in:           "1:1:1:2",
+			sampledFlag:  false,
+			debugFlag:    true,
+			firehoseFlag: false,
+		},
+
+		"IsFirehose Only": {
+			in:           "1:1:1:8",
+			sampledFlag:  false,
+			debugFlag:    false,
+			firehoseFlag: true,
+		},
+
+		"Sampled And Debug": {
+			in:           "1:1:1:3",
+			sampledFlag:  true,
+			debugFlag:    true,
+			firehoseFlag: false,
+		},
+
+		"Sampled And Firehose": {
+			in:           "1:1:1:9",
+			sampledFlag:  true,
+			debugFlag:    false,
+			firehoseFlag: true,
+		},
+
+		"Debug And Firehose": {
+			in:           "1:1:1:10",
+			sampledFlag:  false,
+			debugFlag:    true,
+			firehoseFlag: true,
+		},
+
+		"Sampled And Debug And Firehose": {
+			in:           "1:1:1:11",
+			sampledFlag:  true,
+			debugFlag:    true,
+			firehoseFlag: true,
+		},
+	}
+
+	for name, tc := range tests {
+		t.Run(name, func(t *testing.T) {
+			ctx, err := ContextFromString(tc.in)
+			require.NoError(t, err)
+			assert.Equal(t, tc.sampledFlag, ctx.IsSampled())
+			assert.Equal(t, tc.debugFlag, ctx.IsDebug())
+			assert.Equal(t, tc.firehoseFlag, ctx.IsFirehose())
+		})
+	}
 }
 
 func TestSpanContext_CopyFrom(t *testing.T) {

span.go

@@ -318,3 +318,8 @@ func setSamplingPriority(s *Span, value interface{}) bool {
 	}
 	return false
 }
+
+// EnableFirehose enables firehose flag on the span context
+func EnableFirehose(s *Span) {
+	s.context.flags |= flagFirehose
+}

span_test.go

@@ -126,6 +126,18 @@ func TestSetTag_SamplingPriority(t *testing.T) {
 	assert.False(t, sp1.context.IsDebug(), "debug should not be allowed by the throttler")
 }
 
+func TestSetFirehoseMode(t *testing.T) {
+	tracer, closer := NewTracer("DOOP", NewConstSampler(true), NewNullReporter())
+	defer closer.Close()
+
+	sp1 := tracer.StartSpan("s1").(*Span)
+	assert.False(t, sp1.context.IsFirehose())
+
+	EnableFirehose(sp1)
+
+	assert.True(t, sp1.context.IsFirehose())
+}
+
 type testThrottler struct {
 	allowAll bool
 }