internal/telemetry: add type safe tag keys

This changes the way keys work, there is still a single internal key
implementation for performance reasons, but the public interface is a set of key
implementations that have type safe Of and Get methods.
This also hides the implemenation of Tag so that we can modify the storage form
and find a more efficient storage if needed.

Change-Id: I6a39cc75c2824c6a92e52d59f16e82e876f16e9c
Reviewed-on: https://go-review.googlesource.com/c/tools/+/223137
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

4 files changed, 29 insertions, 37 deletions

diff --git a/internal/lsp/debug/metrics.go b/internal/lsp/debug/metrics.go
index 19ac0a1f3..09e2a9405 100644
--- a/internal/lsp/debug/metrics.go
+++ b/internal/lsp/debug/metrics.go
@@ -18,33 +18,33 @@ var (
 	receivedBytes = metric.HistogramInt64{
 		Name:        "received_bytes",
 		Description: "Distribution of received bytes, by method.",
-		Keys:        []*event.Key{tag.RPCDirection, tag.Method},
+		Keys:        []event.Key{tag.RPCDirection, tag.Method},
 		Buckets:     bytesDistribution,
 	}.Record(tag.ReceivedBytes)
 
 	sentBytes = metric.HistogramInt64{
 		Name:        "sent_bytes",
 		Description: "Distribution of sent bytes, by method.",
-		Keys:        []*event.Key{tag.RPCDirection, tag.Method},
+		Keys:        []event.Key{tag.RPCDirection, tag.Method},
 		Buckets:     bytesDistribution,
 	}.Record(tag.SentBytes)
 
 	latency = metric.HistogramFloat64{
 		Name:        "latency",
 		Description: "Distribution of latency in milliseconds, by method.",
-		Keys:        []*event.Key{tag.RPCDirection, tag.Method},
+		Keys:        []event.Key{tag.RPCDirection, tag.Method},
 		Buckets:     millisecondsDistribution,
 	}.Record(tag.Latency)
 
 	started = metric.Scalar{
 		Name:        "started",
 		Description: "Count of RPCs started by method.",
-		Keys:        []*event.Key{tag.RPCDirection, tag.Method},
+		Keys:        []event.Key{tag.RPCDirection, tag.Method},
 	}.CountInt64(tag.Started)
 
 	completed = metric.Scalar{
 		Name:        "completed",
 		Description: "Count of RPCs completed by method and status.",
-		Keys:        []*event.Key{tag.RPCDirection, tag.Method, tag.StatusCode},
+		Keys:        []event.Key{tag.RPCDirection, tag.Method, tag.StatusCode},
 	}.CountFloat64(tag.Latency)
 )
diff --git a/internal/lsp/debug/rpc.go b/internal/lsp/debug/rpc.go
index 07aed82d4..11f45d4dc 100644
--- a/internal/lsp/debug/rpc.go
+++ b/internal/lsp/debug/rpc.go
@@ -8,7 +8,6 @@ import (
 	"context"
 	"fmt"
 	"html/template"
-	"log"
 	"net/http"
 	"sort"
 	"sync"
@@ -97,13 +96,10 @@ func (r *rpcs) Metric(ctx context.Context, data event.MetricData) {
 	defer r.mu.Unlock()
 	for i, group := range data.Groups() {
 		set := &r.Inbound
-		if group.Get(tag.RPCDirection) == tag.Outbound {
+		if tag.RPCDirection.Get(group) == tag.Outbound {
 			set = &r.Outbound
 		}
-		method, ok := group.Get(tag.Method).(string)
-		if !ok {
-			continue
-		}
+		method := tag.Method.Get(group)
 		index := sort.Search(len(*set), func(i int) bool {
 			return (*set)[i].Method >= method
 		})
@@ -119,11 +115,7 @@ func (r *rpcs) Metric(ctx context.Context, data event.MetricData) {
 		case started:
 			stats.Started = data.(*metric.Int64Data).Rows[i]
 		case completed:
-			status, ok := group.Get(tag.StatusCode).(string)
-			if !ok {
-				log.Printf("Not status... %v", group)
-				continue
-			}
+			status := tag.StatusCode.Get(group)
 			var b *rpcCodeBucket
 			for c, entry := range stats.Codes {
 				if entry.Key == status {
diff --git a/internal/lsp/debug/tag/tag.go b/internal/lsp/debug/tag/tag.go
index 389fd9084..b9743969d 100644
--- a/internal/lsp/debug/tag/tag.go
+++ b/internal/lsp/debug/tag/tag.go
@@ -13,27 +13,27 @@ import (
 
 var (
 	// create the tag keys we use
-	Method        = &event.Key{Name: "method"}
-	StatusCode    = &event.Key{Name: "status.code"}
-	StatusMessage = &event.Key{Name: "status.message"}
-	RPCID         = &event.Key{Name: "id"}
-	RPCDirection  = &event.Key{Name: "direction"}
-	File          = &event.Key{Name: "file"}
-	Directory     = &event.Key{Name: "directory"}
-	URI           = &event.Key{Name: "URI"}
-	Package       = &event.Key{Name: "package"}
-	PackagePath   = &event.Key{Name: "package_path"}
-	Query         = &event.Key{Name: "query"}
-	Snapshot      = &event.Key{Name: "snapshot"}
-	Operation     = &event.Key{Name: "operation"}
+	Method        = event.NewStringKey("method", "")
+	StatusCode    = event.NewStringKey("status.code", "")
+	StatusMessage = event.NewStringKey("status.message", "")
+	RPCID         = event.NewStringKey("id", "")
+	RPCDirection  = event.NewStringKey("direction", "")
+	File          = event.NewStringKey("file", "")
+	Directory     = event.NewKey("directory", "")
+	URI           = event.NewKey("URI", "")
+	Package       = event.NewStringKey("package", "")
+	PackagePath   = event.NewStringKey("package_path", "")
+	Query         = event.NewKey("query", "")
+	Snapshot      = event.NewUInt64Key("snapshot", "")
+	Operation     = event.NewStringKey("operation", "")
 
-	Position     = &event.Key{Name: "position"}
-	Category     = &event.Key{Name: "category"}
-	PackageCount = &event.Key{Name: "packages"}
-	Files        = &event.Key{Name: "files"}
-	Port         = &event.Key{Name: "port"}
-	Type         = &event.Key{Name: "type"}
-	HoverKind    = &event.Key{Name: "hoverkind"}
+	Position     = event.NewKey("position", "")
+	Category     = event.NewStringKey("category", "")
+	PackageCount = event.NewIntKey("packages", "")
+	Files        = event.NewKey("files", "")
+	Port         = event.NewIntKey("port", "")
+	Type         = event.NewKey("type", "")
+	HoverKind    = event.NewStringKey("hoverkind", "")
 )
 
 var (
diff --git a/internal/lsp/debug/trace.go b/internal/lsp/debug/trace.go
index 907c4bd70..e32af8cf2 100644
--- a/internal/lsp/debug/trace.go
+++ b/internal/lsp/debug/trace.go
@@ -172,7 +172,7 @@ func fillOffsets(td *traceData, start time.Time) {
 func renderTags(tags event.TagList) string {
 	buf := &bytes.Buffer{}
 	for _, tag := range tags {
-		fmt.Fprintf(buf, "%v=%q ", tag.Key, tag.Value)
+		fmt.Fprintf(buf, "%s=%q ", tag.Key().Name(), tag.Value())
 	}
 	return buf.String()
 }