plugins: set OTEL_RESOURCE_ATTRIBUTES when invoking a plugin

When a plugin is invoked, the docker cli will now set
`OTEL_RESOURCE_ATTRIBUTES` to pass OTEL resource attribute names to the
plugin as additional resource attributes. At the moment, the only
resource attribute passed is `cobra.command_path`.

All resource attributes passed by the CLI are prepended with the
namespace `docker.cli` to avoid clashing with existing ones the plugin
uses or ones defined by the user.

For aliased commands like the various builder commands, the command path
is overwritten to match with the original name (such as `docker
builder`) instead of the forwarded name (such as `docker buildx build`).

Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>

cli-plugins/manager/cobra.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/docker/cli/cli/command"
 	"github.com/spf13/cobra"
+	"go.opentelemetry.io/otel/attribute"
 )
 
 const (
@@ -30,6 +31,10 @@ const (
 	// is, one which failed it's candidate test) and contains the
 	// reason for the failure.
 	CommandAnnotationPluginInvalid = "com.docker.cli.plugin-invalid"
+
+	// CommandAnnotationPluginCommandPath is added to overwrite the
+	// command path for a plugin invocation.
+	CommandAnnotationPluginCommandPath = "com.docker.cli.plugin.command_path"
 )
 
 var pluginCommandStubsOnce sync.Once
@@ -98,3 +103,38 @@ func AddPluginCommandStubs(dockerCli command.Cli, rootCmd *cobra.Command) (err e
 	})
 	return err
 }
+
+const (
+	dockerCliAttributePrefix = attribute.Key("docker.cli")
+
+	cobraCommandPath = attribute.Key("cobra.command_path")
+)
+
+func getPluginResourceAttributes(cmd *cobra.Command, plugin Plugin) attribute.Set {
+	commandPath := cmd.Annotations[CommandAnnotationPluginCommandPath]
+	if commandPath == "" {
+		commandPath = fmt.Sprintf("%s %s", cmd.CommandPath(), plugin.Name)
+	}
+
+	attrSet := attribute.NewSet(
+		cobraCommandPath.String(commandPath),
+	)
+
+	kvs := make([]attribute.KeyValue, 0, attrSet.Len())
+	for iter := attrSet.Iter(); iter.Next(); {
+		attr := iter.Attribute()
+		kvs = append(kvs, attribute.KeyValue{
+			Key:   dockerCliAttributePrefix + "." + attr.Key,
+			Value: attr.Value,
+		})
+	}
+	return attribute.NewSet(kvs...)
+}
+
+func appendPluginResourceAttributesEnvvar(env []string, cmd *cobra.Command, plugin Plugin) []string {
+	if attrs := getPluginResourceAttributes(cmd, plugin); attrs.Len() > 0 {
+		envVarVal := attrs.Encoded(attribute.DefaultEncoder())
+		env = append(env, ResourceAttributesEnvvar+"="+envVarVal)
+	}
+	return env
+}

cli-plugins/manager/manager.go

@@ -17,11 +17,17 @@ import (
 	"golang.org/x/sync/errgroup"
 )
 
+const (
 	// ReexecEnvvar is the name of an ennvar which is set to the command
 	// used to originally invoke the docker CLI when executing a
 	// plugin. Assuming $PATH and $CWD remain unchanged this should allow
 	// the plugin to re-execute the original CLI.
-const ReexecEnvvar = "DOCKER_CLI_PLUGIN_ORIGINAL_CLI_COMMAND"
+	ReexecEnvvar = "DOCKER_CLI_PLUGIN_ORIGINAL_CLI_COMMAND"
+
+	// ResourceAttributesEnvvar is the name of the envvar that includes additional
+	// resource attributes for OTEL.
+	ResourceAttributesEnvvar = "OTEL_RESOURCE_ATTRIBUTES"
+)
 
 // errPluginNotFound is the error returned when a plugin could not be found.
 type errPluginNotFound string
@@ -236,6 +242,7 @@ func PluginRunCommand(dockerCli command.Cli, name string, rootcmd *cobra.Command
 
 		cmd.Env = os.Environ()
 		cmd.Env = append(cmd.Env, ReexecEnvvar+"="+os.Args[0])
+		cmd.Env = appendPluginResourceAttributesEnvvar(cmd.Env, rootcmd, plugin)
 
 		return cmd, nil
 	}

cmd/docker/builder.go

@@ -69,7 +69,7 @@ func processBuilder(dockerCli command.Cli, cmd *cobra.Command, args, osargs []st
 	}
 
 	// is this a build that should be forwarded to the builder?
-	fwargs, fwosargs, forwarded := forwardBuilder(builderAlias, args, osargs)
+	fwargs, fwosargs, alias, forwarded := forwardBuilder(builderAlias, args, osargs)
 	if !forwarded {
 		return args, osargs, nil, nil
 	}
@@ -116,10 +116,13 @@ func processBuilder(dockerCli command.Cli, cmd *cobra.Command, args, osargs []st
 		envs = append([]string{"BUILDX_BUILDER=" + dockerCli.CurrentContext()}, envs...)
 	}
 
+	// overwrite the command path for this plugin using the alias name.
+	cmd.Annotations[pluginmanager.CommandAnnotationPluginCommandPath] = fmt.Sprintf("%s %s", cmd.CommandPath(), alias)
+
 	return fwargs, fwosargs, envs, nil
 }
 
-func forwardBuilder(alias string, args, osargs []string) ([]string, []string, bool) {
+func forwardBuilder(alias string, args, osargs []string) ([]string, []string, string, bool) {
 	aliases := [][2][]string{
 		{
 			{"builder"},
@@ -137,10 +140,10 @@ func forwardBuilder(alias string, args, osargs []string) ([]string, []string, bo
 	for _, al := range aliases {
 		if fwargs, changed := command.StringSliceReplaceAt(args, al[0], al[1], 0); changed {
 			fwosargs, _ := command.StringSliceReplaceAt(osargs, al[0], al[1], -1)
-			return fwargs, fwosargs, true
+			return fwargs, fwosargs, al[0][0], true
 		}
 	}
-	return args, osargs, false
+	return args, osargs, "", false
 }
 
 // hasBuilderName checks if a builder name is defined in args or env vars

vendor.mod

@@ -37,6 +37,7 @@ require (
 	github.com/theupdateframework/notary v0.7.1-0.20210315103452-bf96a202a09a
 	github.com/tonistiigi/go-rosetta v0.0.0-20200727161949-f79598599c5d
 	github.com/xeipuuv/gojsonschema v1.2.0
+	go.opentelemetry.io/otel v1.21.0
 	golang.org/x/sync v0.6.0
 	golang.org/x/sys v0.16.0
 	golang.org/x/term v0.15.0
@@ -77,7 +78,6 @@ require (
 	github.com/xeipuuv/gojsonreference v0.0.0-20180127040603-bd5ef7bd5415 // indirect
 	go.etcd.io/etcd/raft/v3 v3.5.6 // indirect
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.46.1 // indirect
-	go.opentelemetry.io/otel v1.21.0 // indirect
 	go.opentelemetry.io/otel/metric v1.21.0 // indirect
 	go.opentelemetry.io/otel/trace v1.21.0 // indirect
 	golang.org/x/crypto v0.17.0 // indirect