adding metrics command into CLI

Makefile

@@ -26,6 +26,7 @@ generate: deps
 	mockgen --destination ./internal/mocks/cloud_computing_regions_service.go --package=mocks --source ./vendor/github.com/serverscom/serverscom-go-client/pkg/cloud_computing_regions.go
 	mockgen --destination ./internal/mocks/cloud_block_storage_volumes_service.go --package=mocks --source ./vendor/github.com/serverscom/serverscom-go-client/pkg/cloud_block_storage_volumes.go
 	mockgen --destination ./internal/mocks/cloud_block_storage_backups_service.go --package=mocks --source ./vendor/github.com/serverscom/serverscom-go-client/pkg/cloud_block_storage_backups.go
+	mockgen --destination ./internal/mocks/metrics_service.go --package=mocks --source ./vendor/github.com/serverscom/serverscom-go-client/pkg/metrics.go
 	sed -i '' 's|github.com/serverscom/srvctl/vendor/github.com/serverscom/serverscom-go-client/pkg|github.com/serverscom/serverscom-go-client/pkg|g' \
 	./internal/mocks/ssh_service.go \
 	./internal/mocks/hosts_service.go \
@@ -43,7 +44,8 @@ generate: deps
 	./internal/mocks/cloud_instances_service.go \
 	./internal/mocks/cloud_computing_regions_service.go \
 	./internal/mocks/cloud_block_storage_volumes_service.go \
-	./internal/mocks/cloud_block_storage_backups_service.go
+	./internal/mocks/cloud_block_storage_backups_service.go \
+	./internal/mocks/metrics_service.go
 
 docs:
 	go run cmd/gendoc/main.go

cmd/base/hooks.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"html/template"
 	"os"
+	"slices"
 	"strings"
 
 	"github.com/serverscom/srvctl/internal/client"
@@ -63,8 +64,17 @@ func InitCmdContext(cmdContext *CmdContext) func(cmd *cobra.Command, args []stri
 	}
 }
 
+// defaultPassThroughOutputs are output formats printed as is by most commands
+var defaultPassThroughOutputs = []string{"json", "yaml"}
+
 // CheckFormatterFlags checks flags related to formatter
 func CheckFormatterFlags(cmdContext *CmdContext, entities map[string]entities.EntityInterface) func(cmd *cobra.Command, args []string) error {
+	return CheckFormatterFlagsWithOutputs(cmdContext, entities, defaultPassThroughOutputs)
+}
+
+// CheckFormatterFlagsWithOutputs checks flags related to formatter, allowing the
+// "text" output plus the given pass-through outputs, that need no further checks
+func CheckFormatterFlagsWithOutputs(cmdContext *CmdContext, entities map[string]entities.EntityInterface, passThroughOutputs []string) func(cmd *cobra.Command, args []string) error {
 	return func(cmd *cobra.Command, args []string) error {
 		if entities == nil {
 			return fmt.Errorf("entities is not initialized")
@@ -87,12 +97,13 @@ func CheckFormatterFlags(cmdContext *CmdContext, entities map[string]entities.En
 		}
 
 		output := formatter.GetOutput()
-		switch output {
-		case "json", "yaml":
-			return nil
-		case "text":
-		default:
-			return fmt.Errorf("invalid output %q, allowed values: json, text, yaml", output)
+		if output != "text" {
+			if slices.Contains(passThroughOutputs, output) {
+				return nil
+			}
+			allowed := append(slices.Clone(passThroughOutputs), "text")
+			slices.Sort(allowed)
+			return fmt.Errorf("invalid output %q, allowed values: %s", output, strings.Join(allowed, ", "))
 		}
 
 		tmpl := formatter.GetTemplateStr()

cmd/entities/metrics/hosts.go

@@ -0,0 +1,69 @@
+package metrics
+
+import (
+	"log"
+
+	"github.com/serverscom/srvctl/cmd/base"
+	"github.com/serverscom/srvctl/internal/metrics"
+	"github.com/serverscom/srvctl/internal/output/entities"
+	"github.com/spf13/cobra"
+)
+
+func newHostsCmd(cmdContext *base.CmdContext) *cobra.Command {
+	hostMetricEntity, err := entities.Registry.GetEntityFromValue(metrics.HostMetric{})
+	if err != nil {
+		log.Fatal(err)
+	}
+	entitiesMap := make(map[string]entities.EntityInterface)
+	entitiesMap["hosts"] = hostMetricEntity
+
+	cmd := &cobra.Command{
+		Use:   "hosts",
+		Short: "Get hosts metrics",
+		Long: "Get hosts metrics: monthly traffic per host.\n\n" +
+			"Use --output raw to get metrics in the Prometheus text exposition format as returned by the API.",
+		PersistentPreRunE: base.CombinePreRunE(
+			base.CheckFormatterFlagsWithOutputs(cmdContext, entitiesMap, []string{rawOutput}),
+			checkPaginationFlags(cmdContext),
+		),
+		Args: base.NoArgs,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			manager := cmdContext.GetManager()
+
+			ctx, cancel := base.SetupContext(cmd, manager)
+			defer cancel()
+
+			base.SetupProxy(cmd, manager)
+
+			scClient := cmdContext.GetClient().SetVerbose(manager.GetVerbose(cmd)).GetScClient()
+
+			raw, err := scClient.Metrics.ListHostsMetrics(ctx)
+			if err != nil {
+				return err
+			}
+
+			formatter := cmdContext.GetOrCreateFormatter(cmd)
+			if formatter.GetOutput() == rawOutput {
+				return printRaw(cmd, raw)
+			}
+
+			samples, err := metrics.Parse(raw)
+			if err != nil {
+				return err
+			}
+
+			rows := metrics.BuildHostRows(samples)
+
+			rows, err = paginate(cmd, rows)
+			if err != nil {
+				return err
+			}
+
+			return formatter.Format(rows)
+		},
+	}
+
+	addFlags(cmd)
+
+	return cmd
+}

cmd/entities/metrics/metrics.go

@@ -0,0 +1,27 @@
+package metrics
+
+import (
+	"github.com/serverscom/srvctl/cmd/base"
+	"github.com/spf13/cobra"
+)
+
+func NewCmd(cmdContext *base.CmdContext) *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "metrics",
+		Short: "Get hosts and racks metrics",
+		Long: "Get hosts and racks metrics.\n\n" +
+			"With the default text output metrics are folded into a table with one row per host or rack.\n" +
+			"Use --output raw to get metrics in the Prometheus text exposition format as returned by the API,\n" +
+			"e.g. to feed a Prometheus textfile collector.",
+		PersistentPreRunE: base.CheckEmptyContexts(cmdContext),
+		Args:              base.NoArgs,
+		Run:               base.UsageRun,
+	}
+
+	cmd.AddCommand(
+		newHostsCmd(cmdContext),
+		newRacksCmd(cmdContext),
+	)
+
+	return cmd
+}