add remote host

comp/core/hostname/remotehostnameimpl/hostname.go

@@ -0,0 +1,99 @@
+// Package remotehostnameimpl provides a function to get the hostname from core agent.
+package remotehostnameimpl
+
+import (
+	"context"
+	"time"
+
+	"github.com/avast/retry-go/v4"
+
+	"github.com/DataDog/datadog-agent/pkg/config"
+	pbgo "github.com/DataDog/datadog-agent/pkg/proto/pbgo/core"
+	"github.com/DataDog/datadog-agent/pkg/util/grpc"
+	"github.com/DataDog/datadog-agent/pkg/util/hostname"
+	"github.com/DataDog/datadog-agent/pkg/util/log"
+)
+
+const (
+	// maxAttempts is the maximum number of times we try to get the hostname
+	// from the core-agent before bailing out.
+	maxAttempts = 6
+)
+
+type remotehostimpl struct {
+	hostname string
+}
+
+func (r *remotehostimpl) Get(ctx context.Context) (string, error) {
+	if r.hostname != "" {
+		return r.hostname, nil
+	}
+	hostname, err := utils.GetHostnameWithContextAndFallback(ctx)
+	if err != nil {
+		return "", err
+	}
+	r.hostname = hostname
+	return hostname, nil
+}
+
+func (r *remotehostimpl) GetSafe(ctx context.Context) string {
+	h, _ := r.Get(ctx)
+	return h
+}
+
+func (r *remotehostimpl) GetWithProvider(ctx context.Context) (hostnameinterface.Data, error) {
+	h, err := r.Get(ctx)
+	if err != nil {
+		return hostnameinterface.Data{}, err
+	}
+	return hostnameinterface.Data{
+		Hostname: h,
+		Provider: "remote",
+	}, nil
+}
+
+// getHostnameWithContext attempts to acquire a hostname by connecting to the
+// core agent's gRPC endpoints extending the given context.
+func getHostnameWithContext(ctx context.Context) (string, error) {
+	var hostname string
+	err := retry.Do(func() error {
+		ctx, cancel := context.WithTimeout(ctx, 1*time.Second)
+		defer cancel()
+
+		ipcAddress, err := config.GetIPCAddress()
+		if err != nil {
+			return err
+		}
+
+		client, err := grpc.GetDDAgentClient(ctx, ipcAddress, config.GetIPCPort())
+		if err != nil {
+			return err
+		}
+
+		reply, err := client.GetHostname(ctx, &pbgo.HostnameRequest{})
+		if err != nil {
+			return err
+		}
+
+		log.Debugf("Acquired hostname from gRPC: %s", reply.Hostname)
+
+		hostname = reply.Hostname
+		return nil
+	}, retry.LastErrorOnly(true), retry.Attempts(maxAttempts), retry.Context(ctx))
+	return hostname, err
+}
+
+// getHostnameWithContextAndFallback attempts to acquire a hostname by connecting to the
+// core agent's gRPC endpoints extending the given context, or falls back to local resolution
+func getHostnameWithContextAndFallback(ctx context.Context) (string, error) {
+	hostnameDetected, err := getHostnameWithContext(ctx)
+	if err != nil {
+		log.Warnf("Could not resolve hostname from core-agent: %v", err)
+		hostnameDetected, err = hostname.Get(ctx)
+		if err != nil {
+			return "", err
+		}
+	}
+	log.Infof("Hostname is: %s", hostnameDetected)
+	return hostnameDetected, nil
+}