telemetry: add tracing

- telemetry/tace: add traces throughout code
- telemetry/metrics: nest metrics and trace under telemetry
- telemetry/tace: add service name span to HTTPMetricsHandler.
- telemetry/metrics: removed chain dependency middleware_tests.
- telemetry/metrics: wrap and encapsulate variatic view registration.
- telemetry/tace: add jaeger support for tracing.
- cmd/pomerium: move `parseOptions` to internal/config.
- cmd/pomerium: offload server handling to httputil and sub pkgs.
- httputil: standardize creation/shutdown of http listeners.
- httputil: prefer curve X25519 to P256 when negotiating TLS.
- fileutil: use standardized Getw

Signed-off-by: Bobby DeSimone <bobbydesimone@gmail.com>

internal/telemetry/trace/trace.go

@@ -0,0 +1,74 @@
+package trace // import "github.com/pomerium/pomerium/internal/telemetry/trace"
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/pomerium/pomerium/internal/log"
+
+	"contrib.go.opencensus.io/exporter/jaeger"
+	"go.opencensus.io/trace"
+)
+
+const (
+	JaegerTracingProviderName = "jaeger"
+)
+
+// TracingOptions contains the configurations settings for a http server.
+type TracingOptions struct {
+	// Shared
+	Provider string
+	Service  string
+	Debug    bool
+
+	// Jaeger
+
+	// CollectorEndpoint is the full url to the Jaeger HTTP Thrift collector.
+	// For example, http://localhost:14268/api/traces
+	JaegerCollectorEndpoint string `mapstructure:"tracing_jaeger_collector_endpoint"`
+	// AgentEndpoint instructs exporter to send spans to jaeger-agent at this address.
+	// For example, localhost:6831.
+	JaegerAgentEndpoint string `mapstructure:"tracing_jaeger_agent_endpoint"`
+}
+
+func RegisterTracing(opts *TracingOptions) error {
+	var err error
+	switch opts.Provider {
+	case JaegerTracingProviderName:
+		err = registerJaeger(opts)
+	default:
+		return fmt.Errorf("telemetry/trace: provider %s unknown", opts.Provider)
+	}
+	if err != nil {
+		return err
+	}
+	if opts.Debug {
+		log.Debug().Msg("telemetry/trace: debug on, sample everything")
+		trace.ApplyConfig(trace.Config{DefaultSampler: trace.AlwaysSample()})
+	}
+	log.Debug().Interface("Opts", opts).Msg("telemetry/trace: exporter created")
+	return nil
+}
+
+func registerJaeger(opts *TracingOptions) error {
+	jex, err := jaeger.NewExporter(
+		jaeger.Options{
+			AgentEndpoint:     opts.JaegerAgentEndpoint,
+			CollectorEndpoint: opts.JaegerCollectorEndpoint,
+			ServiceName:       opts.Service,
+		})
+	if err != nil {
+		return err
+	}
+	trace.RegisterExporter(jex)
+	return nil
+}
+
+// StartSpan starts a new child span of the current span in the context. If
+// there is no span in the context, creates a new trace and span.
+//
+// Returned context contains the newly created span. You can use it to
+// propagate the returned span in process.
+func StartSpan(ctx context.Context, name string, o ...trace.StartOption) (context.Context, *trace.Span) {
+	return trace.StartSpan(ctx, name, o...)
+}