metrics, client: fix string type writing

client.go

@@ -184,6 +184,11 @@ func (c *PCPClient) initializeSingletonMetricOffsets(metric *PCPSingletonMetric,
 	metric.valueoffset = *valuesoffset
 	*valuesoffset += ValueLength
 
+	if metric.t == StringType {
+		metric.val.(*PCPString).offset = *stringsoffset
+		*stringsoffset += StringLength
+	}
+
 	if metric.shortDescription.val != "" {
 		metric.shortDescription.offset = *stringsoffset
 		*stringsoffset += StringLength
@@ -202,6 +207,11 @@ func (c *PCPClient) initializeInstanceMetricOffsets(metric *PCPInstanceMetric, m
 	for name := range metric.indom.instances {
 		metric.vals[name].offset = *valuesoffset
 		*valuesoffset += ValueLength
+
+		if metric.t == StringType {
+			metric.vals[name].val.(*PCPString).offset = *stringsoffset
+			*stringsoffset += StringLength
+		}
 	}
 
 	if metric.shortDescription.val != "" {
@@ -388,7 +398,7 @@ func (c *PCPClient) writeInstance(t MetricType, val interface{}, valueoffset int
 		c.buffer.MustWriteUint64(uint64(offset))
 	}
 
-	update := newupdateClosure(offset, c.buffer, t)
+	update := newupdateClosure(offset, c.buffer)
 	_ = update(val)
 
 	c.buffer.MustSetPos(valueoffset + MaxDataValueSize)

metrics.go

@@ -354,14 +354,12 @@ func (md *PCPMetricDesc) Description() string {
 type updateClosure func(interface{}) error
 
 // newupdateClosure creates a new update closure for an offset, type and buffer
-func newupdateClosure(offset int, buffer bytebuffer.Buffer, t MetricType) updateClosure {
+func newupdateClosure(offset int, buffer bytebuffer.Buffer) updateClosure {
 	return func(val interface{}) error {
-		if t == StringType {
+		if _, isString := val.(string); isString {
 			buffer.MustSetPos(offset)
 			buffer.MustWrite(make([]byte, StringLength))
-			val = val.(*PCPString).val
 		}
-
 		buffer.MustSetPos(offset)
 		return buffer.WriteVal(val)
 	}
@@ -411,8 +409,6 @@ func (m *PCPSingletonMetric) Set(val interface{}) error {
 		return errors.New("the value is incompatible with this metrics MetricType")
 	}
 
-	val = m.t.resolve(val)
-
 	if val != m.val {
 		m.Lock()
 		defer m.Unlock()
@@ -516,22 +512,28 @@ func (m *PCPInstanceMetric) ValInstance(instance string) (interface{}, error) {
 
 // SetInstance sets the value for a particular instance of the metric
 func (m *PCPInstanceMetric) SetInstance(instance string, val interface{}) error {
+	if !m.t.IsCompatible(val) {
+		return errors.New("the value is incompatible with this metrics MetricType")
+	}
+
 	if !m.indom.HasInstance(instance) {
 		return fmt.Errorf("%v is not an instance of this metric", instance)
 	}
 
-	m.Lock()
-	defer m.Unlock()
+	if m.vals[instance].val != val {
+		m.Lock()
+		defer m.Unlock()
 
-	val = m.t.resolve(val)
-	if m.vals[instance].update != nil {
-		err := m.vals[instance].update(val)
-		if err != nil {
-			return err
+		if m.vals[instance].update != nil {
+			err := m.vals[instance].update(val)
+			if err != nil {
+				return err
+			}
 		}
+
+		m.vals[instance].val = val
 	}
 
-	m.vals[instance].val = val
 	return nil
 }