envoy: Enable zipkin tracing (#737)

- Update envoy bootstrap config to protobufs
- Reorganize tracing config to avoid cyclic import
- Push down zipkin config to Envoy
- Update tracing options to provide sample rate

config/trace_test.go

@@ -0,0 +1,79 @@
+package config
+
+import (
+	"net/url"
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_NewTracingOptions(t *testing.T) {
+	tests := []struct {
+		name    string
+		opts    *Options
+		want    *TracingOptions
+		wantErr bool
+	}{
+		{
+			"jaeger_good",
+			&Options{TracingProvider: "jaeger", TracingJaegerAgentEndpoint: "foo", TracingJaegerCollectorEndpoint: "http://foo"},
+			&TracingOptions{Provider: "jaeger", JaegerAgentEndpoint: "foo", JaegerCollectorEndpoint: &url.URL{Scheme: "http", Host: "foo"}},
+			false,
+		},
+		{
+			"jaeger_bad",
+			&Options{TracingProvider: "jaeger", TracingJaegerAgentEndpoint: "foo", TracingJaegerCollectorEndpoint: "badurl"},
+			nil,
+			true,
+		},
+		{
+			"zipkin_good",
+			&Options{TracingProvider: "zipkin", ZipkinEndpoint: "https://foo/api/v1/spans"},
+			&TracingOptions{Provider: "zipkin", ZipkinEndpoint: &url.URL{Scheme: "https", Host: "foo", Path: "/api/v1/spans"}},
+			false,
+		},
+		{
+			"zipkin_bad",
+			&Options{TracingProvider: "zipkin", ZipkinEndpoint: "notaurl"},
+			nil,
+			true,
+		},
+		{
+			"noprovider",
+			&Options{},
+			&TracingOptions{},
+			false,
+		},
+		{
+			"fakeprovider",
+			&Options{TracingProvider: "fake"},
+			nil,
+			true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := NewTracingOptions(tt.opts)
+			assert.NotEqual(t, err == nil, tt.wantErr, "unexpected error value")
+			assert.Empty(t, cmp.Diff(tt.want, got))
+		})
+	}
+}
+
+func Test_TracingEnabled(t *testing.T) {
+	tests := []struct {
+		name string
+		opts *TracingOptions
+		want bool
+	}{
+		{"enabled", &TracingOptions{Provider: "zipkin"}, true},
+		{"not enabled", &TracingOptions{}, false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			assert.Equal(t, tt.want, tt.opts.Enabled(), "unexpected tracing state")
+		})
+	}
+}