Use github.com/ugorji/go/codec/ for wiring messages

* New encoding format:
  * Msgpack reports between probe<->app (smaller representation, faster to
    encode/decode).
  * Still use JSON between app<->UI (try to avoid making javascript deal with
    mspack).

  The app still suports publishing reports in both gob and JSON, not braking
  backwards compatibility.

* Use compile-time generated marshallers/unmarshallers for higher performance. In
  order to be able to skip code-generation for certain types, I included
  https://github.com/2opremio/go-1/tree/master/codec/codecgen instead of
  upstream until https://github.com/ugorji/go/pull/139 is merged.

* Encode/decode intermediate types using github.com/ugorji/go/codec.Selfer
  for higher performance and reducing garbage collection (no temporary buffers).

render/benchmark_test.go

@@ -1,11 +1,12 @@
 package render_test
 
 import (
-	"encoding/json"
 	"flag"
 	"io/ioutil"
 	"testing"
 
+	"github.com/ugorji/go/codec"
+
 	"github.com/weaveworks/scope/render"
 	"github.com/weaveworks/scope/report"
 	"github.com/weaveworks/scope/test/fixture"
@@ -94,6 +95,6 @@ func loadReport() (report.Report, error) {
 		return rpt, err
 	}
 	rpt := report.MakeReport()
-	err = json.Unmarshal(b, &rpt)
+	err = codec.NewDecoderBytes(b, &codec.JsonHandle{}).Decode(&rpt)
 	return rpt, err
 }

render/detailed/metadata.go

@@ -1,10 +1,12 @@
 package detailed
 
 import (
-	"encoding/json"
+	"bytes"
 	"strconv"
 	"strings"
 
+	"github.com/ugorji/go/codec"
+
 	"github.com/weaveworks/scope/probe/docker"
 	"github.com/weaveworks/scope/probe/host"
 	"github.com/weaveworks/scope/probe/kubernetes"
@@ -120,7 +122,9 @@ func (m MetadataRow) Copy() MetadataRow {
 // MarshalJSON marshals this MetadataRow to json. It adds a label before
 // rendering.
 func (m MetadataRow) MarshalJSON() ([]byte, error) {
-	return json.Marshal(struct {
+	buf := bytes.Buffer{}
+	encoder := codec.NewEncoder(&buf, &codec.JsonHandle{})
+	err := encoder.Encode(struct {
 		ID    string `json:"id"`
 		Label string `json:"label"`
 		Value string `json:"value"`
@@ -131,6 +135,7 @@ func (m MetadataRow) MarshalJSON() ([]byte, error) {
 		Value: m.Value,
 		Prime: m.Prime,
 	})
+	return buf.Bytes(), err
 }
 
 // NodeMetadata produces a table (to be consumed directly by the UI) based on

render/detailed/metrics.go

@@ -1,9 +1,10 @@
 package detailed
 
 import (
-	"encoding/json"
+	"bytes"
 	"math"
 
+	"github.com/ugorji/go/codec"
 	"github.com/weaveworks/scope/probe/docker"
 	"github.com/weaveworks/scope/probe/host"
 	"github.com/weaveworks/scope/probe/process"
@@ -62,7 +63,9 @@ func (m MetricRow) Copy() MetricRow {
 // MarshalJSON marshals this MetricRow to json. It takes the basic Metric
 // rendering, then adds some row-specific fields.
 func (m MetricRow) MarshalJSON() ([]byte, error) {
-	return json.Marshal(struct {
+	buf := bytes.Buffer{}
+	encoder := codec.NewEncoder(&buf, &codec.JsonHandle{})
+	err := encoder.Encode(struct {
 		ID     string  `json:"id"`
 		Label  string  `json:"label"`
 		Format string  `json:"format,omitempty"`
@@ -77,6 +80,7 @@ func (m MetricRow) MarshalJSON() ([]byte, error) {
 		Value:       m.Value,
 		WireMetrics: m.Metric.ToIntermediate(),
 	})
+	return buf.Bytes(), err
 }
 
 // NodeMetrics produces a table (to be consumed directly by the UI) based on

render/detailed/summary.go

@@ -1,9 +1,10 @@
 package detailed
 
 import (
-	"encoding/json"
 	"fmt"
 
+	"github.com/ugorji/go/codec"
+
 	"github.com/weaveworks/scope/probe/docker"
 	"github.com/weaveworks/scope/probe/host"
 	"github.com/weaveworks/scope/probe/kubernetes"
@@ -37,19 +38,27 @@ func (g NodeSummaryGroup) Copy() NodeSummaryGroup {
 // their label for the frontend.
 type Column string
 
-// MarshalJSON serializes a column to json
-func (c Column) MarshalJSON() ([]byte, error) {
-	return json.Marshal(map[string]string{"id": string(c), "label": Label(string(c))})
+// CodecEncodeSelf implements codec.Selfer
+func (c *Column) CodecEncodeSelf(encoder *codec.Encoder) {
+	in := map[string]string{"id": string(*c), "label": Label(string(*c))}
+	encoder.Encode(in)
 }
 
-// UnmarshalJSON deserializes a column from json
-func (c *Column) UnmarshalJSON(b []byte) error {
+// CodecDecodeSelf implements codec.Selfer
+func (c *Column) CodecDecodeSelf(decoder *codec.Decoder) {
 	m := map[string]string{}
-	if err := json.Unmarshal(b, &m); err != nil {
-		return err
-	}
+	decoder.Decode(&m)
 	*c = Column(m["id"])
-	return nil
+}
+
+// MarshalJSON shouldn't be used, use CodecEncodeSelf instead
+func (Column) MarshalJSON() ([]byte, error) {
+	panic("MarshalJSON shouldn't be used, use CodecEncodeSelf instead")
+}
+
+// UnmarshalJSON shouldn't be used, use CodecDecodeSelf instead
+func (*Column) UnmarshalJSON(b []byte) error {
+	panic("UnmarshalJSON shouldn't be used, use CodecDecodeSelf instead")
 }
 
 // NodeSummary is summary information about a child for a Node.