internal/lsp: add telemetry stubs

This is designed to provide a compatible API to opencensus libraries while we
still cannot directly depend on it.
Most of this will be deleted again when we move the code over into the
sub-module.

Change-Id: I42b561f4f403c18cd22fb909b037f584ea90ad1b
Reviewed-on: https://go-review.googlesource.com/c/tools/+/183247
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>

internal/lsp/debug/serve.go

@@ -19,6 +19,7 @@ import (
 	"strconv"
 	"sync"
 
+	"golang.org/x/tools/internal/lsp/telemetry"
 	"golang.org/x/tools/internal/span"
 )
 
@@ -216,6 +217,7 @@ func Serve(ctx context.Context, addr string) error {
 		mux := http.NewServeMux()
 		mux.HandleFunc("/", Render(mainTmpl, func(*http.Request) interface{} { return data }))
 		mux.HandleFunc("/debug/", Render(debugTmpl, nil))
+		telemetry.Handle(mux)
 		mux.HandleFunc("/debug/pprof/", pprof.Index)
 		mux.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
 		mux.HandleFunc("/debug/pprof/profile", pprof.Profile)
@@ -354,6 +356,8 @@ var debugTmpl = template.Must(template.Must(BaseTemplate.Clone()).Parse(`
 {{define "title"}}GoPls Debug pages{{end}}
 {{define "body"}}
 <a href="/debug/pprof">Profiling</a>
+<a href="/debug/rpcz">RPCz</a>
+<a href="/debug/tracez">Tracez</a>
 {{end}}
 `))
 

internal/lsp/telemetry/stats/stats.go

@@ -0,0 +1,47 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package stats provides support for recording telemetry statistics.
+package stats
+
+import "context"
+
+type Measure interface {
+	Name() string
+	Description() string
+	Unit() string
+}
+
+type Float64Measure interface {
+	Measure
+	M(v float64) Measurement
+}
+
+type Int64Measure interface {
+	Measure
+	M(v int64) Measurement
+}
+
+type Measurement interface {
+	Measure() Measure
+	Value() float64
+}
+
+type nullMeasure struct{}
+type nullFloat64Measure struct{ nullMeasure }
+type nullInt64Measure struct{ nullMeasure }
+
+func (nullMeasure) Name() string        { return "" }
+func (nullMeasure) Description() string { return "" }
+func (nullMeasure) Unit() string        { return "" }
+
+func (nullFloat64Measure) M(v float64) Measurement { return nil }
+func (nullInt64Measure) M(v int64) Measurement     { return nil }
+
+func NullFloat64Measure() Float64Measure { return nullFloat64Measure{} }
+func NullInt64Measure() Int64Measure     { return nullInt64Measure{} }
+
+var (
+	Record = func(ctx context.Context, ms ...Measurement) {}
+)

internal/lsp/telemetry/tag/tag.go

@@ -0,0 +1,32 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package tag adds support for telemetry tags.
+package tag
+
+import "context"
+
+type Map interface{}
+
+type Key interface {
+	Name() string
+}
+
+type Mutator interface {
+	Mutate(Map) (Map, error)
+}
+
+type nullMutator struct{}
+
+func (nullMutator) Mutate(Map) (Map, error) { return nil, nil }
+
+var (
+	New         = func(ctx context.Context, mutator ...Mutator) (context.Context, error) { return ctx, nil }
+	NewContext  = func(ctx context.Context, m Map) context.Context { return ctx }
+	FromContext = func(ctx context.Context) Map { return nil }
+	Delete      = func(k Key) Mutator { return nullMutator{} }
+	Insert      = func(k Key, v string) Mutator { return nullMutator{} }
+	Update      = func(k Key, v string) Mutator { return nullMutator{} }
+	Upsert      = func(k Key, v string) Mutator { return nullMutator{} }
+)

internal/lsp/telemetry/telemetry.go

@@ -0,0 +1,33 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package telemetry provides the hooks and adapters to allow use of telemetry
+// throughout gopls.
+package telemetry
+
+import (
+	"net/http"
+
+	"golang.org/x/tools/internal/lsp/telemetry/stats"
+	"golang.org/x/tools/internal/lsp/telemetry/tag"
+)
+
+var (
+	Handle = func(mux *http.ServeMux) {}
+
+	Started       = stats.NullInt64Measure()
+	ReceivedBytes = stats.NullInt64Measure()
+	SentBytes     = stats.NullInt64Measure()
+	Latency       = stats.NullFloat64Measure()
+
+	KeyRPCID        tag.Key
+	KeyMethod       tag.Key
+	KeyStatus       tag.Key
+	KeyRPCDirection tag.Key
+)
+
+const (
+	Inbound  = "in"
+	Outbound = "out"
+)

internal/lsp/telemetry/trace/trace.go

@@ -0,0 +1,58 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package tag adds support for telemetry tracins.
+package trace
+
+import "context"
+
+type Span interface {
+	AddAttributes(attributes ...Attribute)
+
+	AddMessageReceiveEvent(messageID, uncompressedByteSize, compressedByteSize int64)
+	AddMessageSendEvent(messageID, uncompressedByteSize, compressedByteSize int64)
+	Annotate(attributes []Attribute, str string)
+	Annotatef(attributes []Attribute, format string, a ...interface{})
+	End()
+	IsRecordingEvents() bool
+	SetName(name string)
+	SetStatus(status Status)
+}
+
+type Attribute interface{}
+
+type Status struct {
+	Code    int32
+	Message string
+}
+
+type nullSpan struct{}
+
+func (nullSpan) AddAttributes(attributes ...Attribute)                                            {}
+func (nullSpan) AddMessageReceiveEvent(messageID, uncompressedByteSize, compressedByteSize int64) {}
+func (nullSpan) AddMessageSendEvent(messageID, uncompressedByteSize, compressedByteSize int64)    {}
+func (nullSpan) Annotate(attributes []Attribute, str string)                                      {}
+func (nullSpan) Annotatef(attributes []Attribute, format string, a ...interface{})                {}
+func (nullSpan) End()                                                                             {}
+func (nullSpan) IsRecordingEvents() bool                                                          { return false }
+func (nullSpan) SetName(name string)                                                              {}
+func (nullSpan) SetStatus(status Status)                                                          {}
+
+var (
+	FromContext = func(ctx context.Context) Span { return nullSpan{} }
+	StartSpan   = func(ctx context.Context, name string, options ...interface{}) (context.Context, Span) {
+		return ctx, nullSpan{}
+	}
+	BoolAttribute    = func(key string, value bool) Attribute { return nil }
+	Float64Attribute = func(key string, value float64) Attribute { return nil }
+	Int64Attribute   = func(key string, value int64) Attribute { return nil }
+	StringAttribute  = func(key string, value string) Attribute { return nil }
+	WithSpanKind     = func(spanKind int) interface{} { return nil }
+)
+
+const (
+	SpanKindUnspecified = iota
+	SpanKindServer
+	SpanKindClient
+)