Do not try to determine IP address if it is already passed via tracer…

… tags (jaegertracing#402)

* NewTracer suport passing iptag [fixes jaegertracing#401]

old codes did not support passing a iptag to NewTracer because NewTracer
will overwrite the iptag. Now modify the NewTracer method, make it
support passing iptag

two private method of Tracer add : getTag, setTag
And testing function is also added into tracer_test.go, all test of
NewTracer passed.

Signed-off-by: 吴灿柳 <[email protected]>

* remove a redundant return

remove a redundant return in order to pass GolangCI check

Signed-off-by: 吴灿柳 <[email protected]>

* Delete setTag, add assertions in unit test, etc

1.delete setTag, only use append
2.getTag method return (interface{}, bool) for indicating found or not
3.no validation for external provided iptag, buyer beware
4.unit test add assertions, and remove the fmt print.

Signed-off-by: 吴灿柳 <[email protected]>

tracer.go

@@ -145,7 +145,15 @@ func NewTracer(
 	if hostname, err := os.Hostname(); err == nil {
 		t.tags = append(t.tags, Tag{key: TracerHostnameTagKey, value: hostname})
 	}
-	if ip, err := utils.HostIP(); err == nil {
+	if ipval, ok := t.getTag(TracerIPTagKey); ok {
+		ipv4, err := utils.ParseIPToUint32(ipval.(string))
+		if err != nil {
+			t.hostIPv4 = 0
+			t.logger.Error("Unable to convert the externally provided ip to uint32: " + err.Error())
+		} else {
+			t.hostIPv4 = ipv4
+		}
+	} else if ip, err := utils.HostIP(); err == nil {
 		t.tags = append(t.tags, Tag{key: TracerIPTagKey, value: ip.String()})
 		t.hostIPv4 = utils.PackIPAsUint32(ip)
 	} else {
@@ -347,6 +355,16 @@ func (t *Tracer) Tags() []opentracing.Tag {
 	return tags
 }
 
+// getTag returns the value of specific tag, if not exists, return nil.
+func (t *Tracer) getTag(key string) (interface{}, bool) {
+	for _, tag := range t.tags {
+		if tag.key == key {
+			return tag.value, true
+		}
+	}
+	return nil, false
+}
+
 // newSpan returns an instance of a clean Span object.
 // If options.PoolSpans is true, the spans are retrieved from an object pool.
 func (t *Tracer) newSpan() *Span {

tracer_test.go

@@ -406,6 +406,35 @@ func TestThrottling_DebugHeader(t *testing.T) {
 	assert.False(t, sp.context.IsDebug(), "debug should not be allowed by the throttler")
 }
 
+func TestSetGetTag(t *testing.T) {
+	opentracer, tc := NewTracer("x", NewConstSampler(true), NewNullReporter())
+	tracer := opentracer.(*Tracer)
+	defer tc.Close()
+	value, ok := tracer.getTag(TracerIPTagKey)
+	assert.True(t, ok)
+	_, ok = value.(string)
+	assert.True(t, ok)
+	assert.True(t, tracer.hostIPv4 != 0)
+
+	ipStr := "11.22.33.44"
+	opentracer, tc = NewTracer("x", NewConstSampler(true), NewNullReporter(), TracerOptions.Tag(TracerIPTagKey, ipStr))
+	tracer = opentracer.(*Tracer)
+	defer tc.Close()
+	value, ok = tracer.getTag(TracerIPTagKey)
+	assert.True(t, ok)
+	assert.True(t, value == ipStr)
+	assert.True(t, tracer.hostIPv4 != 0)
+
+	ipStrInvalid := "an invalid input"
+	opentracer, tc = NewTracer("x", NewConstSampler(true), NewNullReporter(), TracerOptions.Tag(TracerIPTagKey, ipStrInvalid))
+	tracer = opentracer.(*Tracer)
+	defer tc.Close()
+	value, ok = tracer.getTag(TracerIPTagKey)
+	assert.True(t, ok)
+	assert.True(t, value == ipStrInvalid)
+	assert.True(t, tracer.hostIPv4 == 0)
+}
+
 type dummyPropagator struct{}
 type dummyCarrier struct {
 	ok bool