LogDog: Add collector service implementation.

server/internal/logdog/config/flag.go

Index: server/internal/logdog/config/flag.go
diff --git a/server/internal/logdog/config/flag.go b/server/internal/logdog/config/flag.go
new file mode 100644
index 0000000000000000000000000000000000000000..69be02f6dea9309276d5762fb04d9d18f4031c2e
--- /dev/null
+++ b/server/internal/logdog/config/flag.go
@@ -0,0 +1,87 @@
+// Copyright 2016 The Chromium 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 config
+
+import (
+	"errors"
+	"flag"
+	"net/http"
+	"time"
+
+	"github.com/luci/luci-go/common/api/logdog_coordinator/services/v1"
+	"github.com/luci/luci-go/common/clock/clockflag"
+	"github.com/luci/luci-go/common/config"
+	"github.com/luci/luci-go/common/config/impl/remote"
+	"github.com/luci/luci-go/common/transport"
+	"golang.org/x/net/context"
+)
+
+// Flags is a set of command-line flags used to set up the process'
+// configuration.
+type Flags struct {
+	// ConfigPath is the path within the ConfigSet of the configuration.
+	//
+	// If ConfigURL is empty, this will be interpreted as a local filesystem path
+	// from which the configuration should be loaded.
+	ConfigFilePath string
+
+	// KillCheckInterval, if >0, starts a goroutine that polls every interval to
+	// see if the configuration has changed.
+	KillCheckInterval clockflag.Duration
+
+	// RoundTripper, if not nil, is the http.RoundTripper that will be used to
+	// fetch remote configurations.
+	RoundTripper http.RoundTripper
+}
+
+// AddToFlagSet augments the supplied FlagSet with values for Flags.
+func (f *Flags) AddToFlagSet(fs *flag.FlagSet) {
+	fs.StringVar(&f.ConfigFilePath, "config-file-path", "",
+		"If set, load the configuration protobuf from this path instead of the configuration service.")
+	fs.Var(&f.KillCheckInterval, "config-kill-interval",
+		"If non-zero, poll for configuration changes and kill the application if one is detected.")
+}
+
+// CoordinatorOptions returns an Options instance loaded from the supplied flags
+// and Coordinator instance.
+func (f *Flags) CoordinatorOptions(c context.Context, client services.ServicesClient) (*Options, error) {
+	ccfg, err := client.GetConfig(c, &services.Void{})

[iannucci, 2016/02/05 23:41:01]

Empty message?

actually you could probably pass nil here, right?

[dnj (Google), 2016/02/06 04:10:37]

That's not how g/pRPC works, unfortunately. It expects an actual message value
in the RPC call.

I finished an implementation of client/server nil passing, but then looked at
gRPC code and noted that it didn't do this, so I retracted.

+	if err != nil {
+		return nil, err
+	}
+
+	// If a ConfigFilePath was specified, use a mock configuration service that
+	// loads from a local file.
+	var ci config.Interface
+	if f.ConfigFilePath != "" {
+		ci = &fileConfig{
+			path:       f.ConfigFilePath,
+			configSet:  ccfg.ConfigSet,
+			configPath: ccfg.ConfigPath,
+		}
+	} else {
+		if ccfg.ConfigServiceUrl == "" {
+			return nil, errors.New("coordinator does not specify a config service")
+		}
+		if ccfg.ConfigSet == "" {
+			return nil, errors.New("coordinator does not specify a config set")
+		}
+		if ccfg.ConfigPath == "" {
+			return nil, errors.New("coordinator does not specify a config path")
+		}
+
+		if f.RoundTripper != nil {
+			c = transport.Set(c, f.RoundTripper)
+		}
+		ci = remote.New(c, ccfg.ConfigServiceUrl)
+	}
+
+	return &Options{
+		Config:            ci,
+		ConfigSet:         ccfg.ConfigSet,
+		ConfigPath:        ccfg.ConfigPath,
+		KillCheckInterval: time.Duration(f.KillCheckInterval),
+	}, nil
+}