swarm: integrate OpenTracing; propagate ctx to internal APIs (#17169)

* swarm: propagate ctx, enable opentracing

* swarm/tracing: log error when tracing is misconfigured

vendor/github.com/uber/jaeger-client-go/internal/throttler/remote/options.go

@@ -0,0 +1,99 @@
+// Copyright (c) 2018 The Jaeger Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package remote
+
+import (
+	"time"
+
+	"github.com/uber/jaeger-client-go"
+)
+
+const (
+	defaultHostPort        = "localhost:5778"
+	defaultRefreshInterval = time.Second * 5
+)
+
+// Option is a function that sets some option on the Throttler
+type Option func(options *options)
+
+// Options is a factory for all available options
+var Options options
+
+type options struct {
+	metrics                   *jaeger.Metrics
+	logger                    jaeger.Logger
+	hostPort                  string
+	refreshInterval           time.Duration
+	synchronousInitialization bool
+}
+
+// Metrics creates an Option that initializes Metrics on the Throttler, which is used to emit statistics.
+func (options) Metrics(m *jaeger.Metrics) Option {
+	return func(o *options) {
+		o.metrics = m
+	}
+}
+
+// Logger creates an Option that sets the logger used by the Throttler.
+func (options) Logger(logger jaeger.Logger) Option {
+	return func(o *options) {
+		o.logger = logger
+	}
+}
+
+// HostPort creates an Option that sets the hostPort of the local agent that keeps track of credits.
+func (options) HostPort(hostPort string) Option {
+	return func(o *options) {
+		o.hostPort = hostPort
+	}
+}
+
+// RefreshInterval creates an Option that sets how often the Throttler will poll local agent for
+// credits.
+func (options) RefreshInterval(refreshInterval time.Duration) Option {
+	return func(o *options) {
+		o.refreshInterval = refreshInterval
+	}
+}
+
+// SynchronousInitialization creates an Option that determines whether the throttler should synchronously
+// fetch credits from the agent when an operation is seen for the first time. This should be set to true
+// if the client will be used by a short lived service that needs to ensure that credits are fetched upfront
+// such that sampling or throttling occurs.
+func (options) SynchronousInitialization(b bool) Option {
+	return func(o *options) {
+		o.synchronousInitialization = b
+	}
+}
+
+func applyOptions(o ...Option) options {
+	opts := options{}
+	for _, option := range o {
+		option(&opts)
+	}
+	if opts.metrics == nil {
+		opts.metrics = jaeger.NewNullMetrics()
+	}
+	if opts.logger == nil {
+		opts.logger = jaeger.NullLogger
+	}
+	if opts.hostPort == "" {
+		opts.hostPort = defaultHostPort
+	}
+	if opts.refreshInterval == 0 {
+		opts.refreshInterval = defaultRefreshInterval
+	}
+	return opts
+}