vpp-maglev/cmd/maglevc/commands.go

// Copyright (c) 2026, Pim van Pelt <pim@ipng.ch>

package main

import (
	"context"
	"fmt"
	"os"
	"strconv"
	"strings"
	"text/tabwriter"
	"time"

	buildinfo "git.ipng.ch/ipng/vpp-maglev/cmd"
	"git.ipng.ch/ipng/vpp-maglev/internal/grpcapi"
)

const callTimeout = 10 * time.Second

// buildTree constructs the full command tree.
func buildTree() *Node {
	root := &Node{Word: "", Help: ""}

	show := &Node{Word: "show", Help: "show information"}
	set := &Node{Word: "set", Help: "modify configuration"}
	quit := &Node{Word: "quit", Help: "exit the shell", Run: runQuit}
	exit := &Node{Word: "exit", Help: "exit the shell", Run: runQuit}

	// show version
	showVersion := &Node{Word: "version", Help: "Show build version", Run: runShowVersion}

	// show frontends [<name>]  — without name: list all, with name: show details
	showFrontendName := &Node{
		Word:    "<name>",
		Help:    "Show details for a single frontend",
		Dynamic: dynFrontends,
		Run:     runShowFrontend,
	}
	showFrontends := &Node{
		Word:     "frontends",
		Help:     "List all frontends",
		Run:      runShowFrontends,
		Children: []*Node{showFrontendName},
	}

	// show backends [<name>]  — without name: list all, with name: show details
	showBackendName := &Node{
		Word:    "<name>",
		Help:    "Show details for a single backend",
		Dynamic: dynBackends,
		Run:     runShowBackend,
	}
	showBackends := &Node{
		Word:     "backends",
		Help:     "List all backends",
		Run:      runShowBackends,
		Children: []*Node{showBackendName},
	}

	// show healthchecks [<name>]  — without name: list all, with name: show details
	showHealthCheckName := &Node{
		Word:    "<name>",
		Help:    "Show details for a single health check",
		Dynamic: dynHealthChecks,
		Run:     runShowHealthCheck,
	}
	showHealthChecks := &Node{
		Word:     "healthchecks",
		Help:     "List all health checks",
		Run:      runShowHealthChecks,
		Children: []*Node{showHealthCheckName},
	}

	// show vpp info / lbstate
	showVPPInfo := &Node{Word: "info", Help: "Show VPP version, uptime, and connection status", Run: runShowVPPInfo}
	showVPPLBState := &Node{Word: "lbstate", Help: "Show VPP load-balancer state (VIPs and application servers)", Run: runShowVPPLBState}
	showVPP := &Node{
		Word:     "vpp",
		Help:     "VPP dataplane information",
		Children: []*Node{showVPPInfo, showVPPLBState},
	}

	show.Children = []*Node{
		showVersion,
		showFrontends,
		showBackends,
		showHealthChecks,
		showVPP,
	}

	// set backend <name> pause|resume|disabled|enabled
	setPause := &Node{Word: "pause", Help: "pause health checking", Run: runPauseBackend}
	setResume := &Node{Word: "resume", Help: "resume health checking", Run: runResumeBackend}
	setDisabled := &Node{Word: "disable", Help: "disable backend (stop probing, remove from rotation)", Run: runDisableBackend}
	setEnabled := &Node{Word: "enable", Help: "enable backend (resume probing)", Run: runEnableBackend}
	setBackendName := &Node{
		Word:     "<name>",
		Help:     "backend name",
		Dynamic:  dynBackends,
		Children: []*Node{setPause, setResume, setDisabled, setEnabled},
	}
	setBackend := &Node{
		Word:     "backend",
		Help:     "modify a backend",
		Children: []*Node{setBackendName},
	}
	// set frontend <name> pool <pool> backend <name> weight <0-100>
	setWeightValue := &Node{
		Word:    "<weight>",
		Help:    "Set weight of a backend in a pool (0-100)",
		Dynamic: dynNone, // accepts any integer; no tab-completion candidates
		Run:     runSetFrontendPoolBackendWeight,
	}
	setFrontendPoolBackendWeight := &Node{Word: "weight", Help: "set backend weight in pool", Children: []*Node{setWeightValue}}
	setFrontendPoolBackendName := &Node{
		Word:     "<backend>",
		Help:     "backend name",
		Dynamic:  dynBackends,
		Children: []*Node{setFrontendPoolBackendWeight},
	}
	setFrontendPoolBackend := &Node{Word: "backend", Help: "select a backend", Children: []*Node{setFrontendPoolBackendName}}
	setFrontendPoolName := &Node{
		Word:     "<pool>",
		Help:     "pool name",
		Dynamic:  dynNone, // pool names aren't listed via gRPC; accepts any input
		Children: []*Node{setFrontendPoolBackend},
	}
	setFrontendPool := &Node{Word: "pool", Help: "select a pool", Children: []*Node{setFrontendPoolName}}
	setFrontendName := &Node{
		Word:     "<name>",
		Help:     "frontend name",
		Dynamic:  dynFrontends,
		Children: []*Node{setFrontendPool},
	}
	setFrontend := &Node{
		Word:     "frontend",
		Help:     "modify a frontend",
		Children: []*Node{setFrontendName},
	}

	set.Children = []*Node{setBackend, setFrontend}

	// watch events [num <n>] [log [level <level>]] [backend] [frontend]
	//
	// All tokens after 'events' are captured as args via a self-referencing slot
	// node. This lets runWatchEvents parse the optional flags manually while still
	// providing tab-completion through the dynamic enumerator.
	var watchEventsOptSlot *Node
	watchEventsOptSlot = &Node{
		Word:    "<opt>",
		Help:    "Stream events with options",
		Dynamic: dynWatchEventOpts,
		Run:     runWatchEvents,
	}
	watchEventsOptSlot.Children = []*Node{watchEventsOptSlot}

	watchEvents := &Node{
		Word:     "events",
		Help:     "stream events (press any key or Ctrl-C to stop)",
		Run:      runWatchEvents,
		Children: []*Node{watchEventsOptSlot},
	}
	watch := &Node{
		Word:     "watch",
		Help:     "watch live event streams",
		Children: []*Node{watchEvents},
	}

	// config check / reload
	configCheck := &Node{Word: "check", Help: "Check configuration file", Run: runConfigCheck}
	configReload := &Node{Word: "reload", Help: "Check and reload configuration", Run: runConfigReload}
	configNode := &Node{
		Word:     "config",
		Help:     "configuration commands",
		Children: []*Node{configCheck, configReload},
	}

	// sync vpp lbstate [<name>]
	//
	// Without a name: run SyncLBStateAll (may remove stale VIPs).
	// With a name: run SyncLBStateVIP(name) for just that frontend (no removals).
	syncVPPLBStateName := &Node{
		Word:    "<name>",
		Help:    "Sync a single frontend's VIP to VPP",
		Dynamic: dynFrontends,
		Run:     runSyncVPPLBState,
	}
	syncVPPLBState := &Node{
		Word:     "lbstate",
		Help:     "Sync the VPP load-balancer dataplane from the running config",
		Run:      runSyncVPPLBState,
		Children: []*Node{syncVPPLBStateName},
	}
	syncVPP := &Node{
		Word:     "vpp",
		Help:     "VPP dataplane sync commands",
		Children: []*Node{syncVPPLBState},
	}
	syncNode := &Node{
		Word:     "sync",
		Help:     "Reconcile dataplane state from the running config",
		Children: []*Node{syncVPP},
	}

	root.Children = []*Node{show, set, watch, configNode, syncNode, quit, exit}
	return root
}

// ---- dynamic enumerators ---------------------------------------------------

func dynFrontends(ctx context.Context, client grpcapi.MaglevClient) []string {
	resp, err := client.ListFrontends(ctx, &grpcapi.ListFrontendsRequest{})
	if err != nil {
		return nil
	}
	return resp.FrontendNames
}

func dynBackends(ctx context.Context, client grpcapi.MaglevClient) []string {
	resp, err := client.ListBackends(ctx, &grpcapi.ListBackendsRequest{})
	if err != nil {
		return nil
	}
	return resp.BackendNames
}

func dynHealthChecks(ctx context.Context, client grpcapi.MaglevClient) []string {
	resp, err := client.ListHealthChecks(ctx, &grpcapi.ListHealthChecksRequest{})
	if err != nil {
		return nil
	}
	return resp.Names
}

// dynNone marks a slot node that accepts any input but provides no
// tab-completion candidates (e.g. a pool name or numeric weight value).
func dynNone(_ context.Context, _ grpcapi.MaglevClient) []string { return nil }

// ---- run functions ---------------------------------------------------------

func runShowVPPInfo(ctx context.Context, client grpcapi.MaglevClient, _ []string) error {
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.GetVPPInfo(ctx, &grpcapi.GetVPPInfoRequest{})
	if err != nil {
		return err
	}
	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintf(w, "%s\t%s\n", label("version"), info.Version)
	fmt.Fprintf(w, "%s\t%s\n", label("build-date"), info.BuildDate)
	fmt.Fprintf(w, "%s\t%s\n", label("build-dir"), info.BuildDirectory)
	fmt.Fprintf(w, "%s\t%d\n", label("vpp-pid"), info.Pid)
	if info.BoottimeNs > 0 {
		bootTime := time.Unix(0, info.BoottimeNs)
		fmt.Fprintf(w, "%s\t%s (%s)\n", label("vpp-boottime"),
			bootTime.Format("2006-01-02 15:04:05"),
			formatDuration(time.Since(bootTime)))
	}
	connTime := time.Unix(0, info.ConnecttimeNs)
	fmt.Fprintf(w, "%s\t%s (%s)\n", label("connected"),
		connTime.Format("2006-01-02 15:04:05"),
		formatDuration(time.Since(connTime)))
	return w.Flush()
}

func runShowVPPLBState(ctx context.Context, client grpcapi.MaglevClient, _ []string) error {
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	state, err := client.GetVPPLBState(ctx, &grpcapi.GetVPPLBStateRequest{})
	if err != nil {
		return err
	}

	// ---- global config ----
	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintf(w, "%s\n", label("global"))
	if state.Conf.Ip4SrcAddress != "" {
		fmt.Fprintf(w, "  %s\t%s\n", label("ip4-src"), state.Conf.Ip4SrcAddress)
	}
	if state.Conf.Ip6SrcAddress != "" {
		fmt.Fprintf(w, "  %s\t%s\n", label("ip6-src"), state.Conf.Ip6SrcAddress)
	}
	fmt.Fprintf(w, "  %s\t%d\n", label("sticky-buckets-per-core"), state.Conf.StickyBucketsPerCore)
	fmt.Fprintf(w, "  %s\t%ds\n", label("flow-timeout"), state.Conf.FlowTimeout)
	if err := w.Flush(); err != nil {
		return err
	}

	if len(state.Vips) == 0 {
		fmt.Println(label("vips") + " (none)")
		return nil
	}

	// ---- per-VIP details ----
	for _, v := range state.Vips {
		fmt.Println()
		w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
		fmt.Fprintf(w, "%s\t%s\n", label("vip"), v.Prefix)
		fmt.Fprintf(w, "  %s\t%s\n", label("protocol"), protoString(v.Protocol))
		fmt.Fprintf(w, "  %s\t%d\n", label("port"), v.Port)
		fmt.Fprintf(w, "  %s\t%s\n", label("encap"), v.Encap)
		fmt.Fprintf(w, "  %s\t%d\n", label("flow-table-length"), v.FlowTableLength)
		fmt.Fprintf(w, "  %s\t%d\n", label("application-servers"), len(v.ApplicationServers))
		if err := w.Flush(); err != nil {
			return err
		}
		for _, a := range v.ApplicationServers {
			fmt.Printf("    %s %s  %s %d  %s %d\n",
				label("address"), a.Address,
				label("weight"), a.Weight,
				label("flow-table-buckets"), a.NumBuckets)
		}
	}
	return nil
}

// protoString renders an IP protocol number as a name (tcp, udp, any, or numeric).
func protoString(p uint32) string {
	switch p {
	case 6:
		return "tcp"
	case 17:
		return "udp"
	case 255:
		return "any"
	}
	return fmt.Sprintf("%d", p)
}

func runSyncVPPLBState(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	req := &grpcapi.SyncVPPLBStateRequest{}
	if len(args) > 0 && args[0] != "" {
		name := args[0]
		req.FrontendName = &name
	}
	if _, err := client.SyncVPPLBState(ctx, req); err != nil {
		return err
	}
	if req.FrontendName != nil {
		fmt.Printf("synced frontend %q to VPP\n", *req.FrontendName)
	} else {
		fmt.Println("synced full LB state to VPP")
	}
	return nil
}

func runShowVersion(_ context.Context, _ grpcapi.MaglevClient, _ []string) error {
	fmt.Printf("maglevc %s (commit %s, built %s)\n",
		buildinfo.Version(), buildinfo.Commit(), buildinfo.Date())
	return nil
}

func runQuit(_ context.Context, _ grpcapi.MaglevClient, _ []string) error {
	return errQuit
}

func runShowFrontends(ctx context.Context, client grpcapi.MaglevClient, _ []string) error {
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	resp, err := client.ListFrontends(ctx, &grpcapi.ListFrontendsRequest{})
	if err != nil {
		return err
	}
	for _, name := range resp.FrontendNames {
		fmt.Println(name)
	}
	return nil
}

func runShowFrontend(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: show frontend <name>")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.GetFrontend(ctx, &grpcapi.GetFrontendRequest{Name: args[0]})
	if err != nil {
		return err
	}

	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintf(w, "%s\t%s\n", label("name"), info.Name)
	fmt.Fprintf(w, "%s\t%s\n", label("address"), info.Address)
	fmt.Fprintf(w, "%s\t%s\n", label("protocol"), info.Protocol)
	fmt.Fprintf(w, "%s\t%d\n", label("port"), info.Port)
	if info.Description != "" {
		fmt.Fprintf(w, "%s\t%s\n", label("description"), info.Description)
	}
	if len(info.Pools) > 0 {
		fmt.Fprintf(w, "%s\n", label("pools"))
	}
	if err := w.Flush(); err != nil {
		return err
	}

	// Pool section uses direct Printf with fixed-width padding so that ANSI
	// escape codes in labels don't confuse tabwriter's byte-based alignment.
	// "backends" is always the widest pool label (8 chars); all pool labels
	// are right-padded to that width, giving a 2+8+2 = 12-char visual indent.
	const poolLblWidth = len("backends")
	const poolIndent = "  "
	const poolSep = "  "
	contIndent := strings.Repeat(" ", len(poolIndent)+poolLblWidth+len(poolSep))

	for _, pool := range info.Pools {
		namePad := strings.Repeat(" ", poolLblWidth-len("name"))
		fmt.Printf("%s%s%s%s%s\n", poolIndent, label("name"), namePad, poolSep, pool.Name)
		for i, pb := range pool.Backends {
			beInfo, beErr := client.GetBackend(ctx, &grpcapi.GetBackendRequest{Name: pb.Name})
			suffix := ""
			if beErr == nil && !beInfo.Enabled {
				suffix = "  [disabled]"
			}
			weightStr := ""
			if pb.Weight != 100 {
				weightStr = fmt.Sprintf("  %s %d", label("weight"), pb.Weight)
			}
			if i == 0 {
				bePad := strings.Repeat(" ", poolLblWidth-len("backends"))
				fmt.Printf("%s%s%s%s%s%s%s\n", poolIndent, label("backends"), bePad, poolSep, pb.Name, weightStr, suffix)
			} else {
				fmt.Printf("%s%s%s%s\n", contIndent, pb.Name, weightStr, suffix)
			}
		}
	}
	return nil
}

func runShowBackends(ctx context.Context, client grpcapi.MaglevClient, _ []string) error {
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	resp, err := client.ListBackends(ctx, &grpcapi.ListBackendsRequest{})
	if err != nil {
		return err
	}
	for _, name := range resp.BackendNames {
		fmt.Println(name)
	}
	return nil
}

func runShowBackend(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: show backend <name>")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.GetBackend(ctx, &grpcapi.GetBackendRequest{Name: args[0]})
	if err != nil {
		return err
	}
	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintf(w, "%s\t%s\n", label("name"), info.Name)
	fmt.Fprintf(w, "%s\t%s\n", label("address"), info.Address)
	stateDur := ""
	if len(info.Transitions) > 0 {
		since := time.Since(time.Unix(0, info.Transitions[0].AtUnixNs))
		stateDur = " for " + formatDuration(since)
	}
	fmt.Fprintf(w, "%s\t%s%s\n", label("state"), info.State, stateDur)
	fmt.Fprintf(w, "%s\t%v\n", label("enabled"), info.Enabled)
	fmt.Fprintf(w, "%s\t%s\n", label("healthcheck"), info.Healthcheck)
	for i, t := range info.Transitions {
		ts := time.Unix(0, t.AtUnixNs)
		var lbl string
		if i == 0 {
			lbl = label("transitions")
		} else {
			// Pad to same visible width as "transitions" and wrap through
			// label() so tabwriter sees the same byte count (ANSI overhead
			// is identical on every row, keeping columns aligned).
			lbl = label("           ")
		}
		fmt.Fprintf(w, "%s\t%s → %s\t%s\t%s\n",
			lbl,
			t.From, t.To,
			ts.Format("2006-01-02 15:04:05.000"),
			formatAgo(time.Since(ts)),
		)
	}
	return w.Flush()
}

func runShowHealthChecks(ctx context.Context, client grpcapi.MaglevClient, _ []string) error {
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	resp, err := client.ListHealthChecks(ctx, &grpcapi.ListHealthChecksRequest{})
	if err != nil {
		return err
	}
	for _, name := range resp.Names {
		fmt.Println(name)
	}
	return nil
}

func runShowHealthCheck(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: show healthcheck <name>")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.GetHealthCheck(ctx, &grpcapi.GetHealthCheckRequest{Name: args[0]})
	if err != nil {
		return err
	}
	w := tabwriter.NewWriter(os.Stdout, 0, 0, 2, ' ', 0)
	fmt.Fprintf(w, "%s\t%s\n", label("name"), info.Name)
	fmt.Fprintf(w, "%s\t%s\n", label("type"), info.Type)
	if info.Port > 0 {
		fmt.Fprintf(w, "%s\t%d\n", label("port"), info.Port)
	}
	fmt.Fprintf(w, "%s\t%s\n", label("interval"), time.Duration(info.IntervalNs))
	if info.FastIntervalNs > 0 {
		fmt.Fprintf(w, "%s\t%s\n", label("fast-interval"), time.Duration(info.FastIntervalNs))
	}
	if info.DownIntervalNs > 0 {
		fmt.Fprintf(w, "%s\t%s\n", label("down-interval"), time.Duration(info.DownIntervalNs))
	}
	fmt.Fprintf(w, "%s\t%s\n", label("timeout"), time.Duration(info.TimeoutNs))
	fmt.Fprintf(w, "%s\t%d\n", label("rise"), info.Rise)
	fmt.Fprintf(w, "%s\t%d\n", label("fall"), info.Fall)
	if info.ProbeIpv4Src != "" {
		fmt.Fprintf(w, "%s\t%s\n", label("probe-ipv4-src"), info.ProbeIpv4Src)
	}
	if info.ProbeIpv6Src != "" {
		fmt.Fprintf(w, "%s\t%s\n", label("probe-ipv6-src"), info.ProbeIpv6Src)
	}
	if h := info.Http; h != nil {
		fmt.Fprintf(w, "%s\t%s\n", label("http.path"), h.Path)
		if h.Host != "" {
			fmt.Fprintf(w, "%s\t%s\n", label("http.host"), h.Host)
		}
		fmt.Fprintf(w, "%s\t%d-%d\n", label("http.response-code"), h.ResponseCodeMin, h.ResponseCodeMax)
		if h.ResponseRegexp != "" {
			fmt.Fprintf(w, "%s\t%s\n", label("http.response-regexp"), h.ResponseRegexp)
		}
	}
	if t := info.Tcp; t != nil {
		fmt.Fprintf(w, "%s\t%v\n", label("tcp.ssl"), t.Ssl)
		if t.ServerName != "" {
			fmt.Fprintf(w, "%s\t%s\n", label("tcp.server-name"), t.ServerName)
		}
	}
	return w.Flush()
}

func runPauseBackend(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: set backend <name> pause")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.PauseBackend(ctx, &grpcapi.BackendRequest{Name: args[0]})
	if err != nil {
		return err
	}
	fmt.Printf("%s: setting state to '%s'\n", info.Name, info.State)
	return nil
}

func runResumeBackend(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: set backend <name> resume")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.ResumeBackend(ctx, &grpcapi.BackendRequest{Name: args[0]})
	if err != nil {
		return err
	}
	fmt.Printf("%s: setting state to '%s'\n", info.Name, info.State)
	return nil
}

func runSetFrontendPoolBackendWeight(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) != 4 {
		return fmt.Errorf("usage: set frontend <name> pool <pool> backend <name> weight <0-100>")
	}
	frontendName, poolName, backendName, weightStr := args[0], args[1], args[2], args[3]
	weight, err := strconv.Atoi(weightStr)
	if err != nil || weight < 0 || weight > 100 {
		return fmt.Errorf("weight: expected integer 0-100, got %q", weightStr)
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.SetFrontendPoolBackendWeight(ctx, &grpcapi.SetWeightRequest{
		Frontend: frontendName,
		Pool:     poolName,
		Backend:  backendName,
		Weight:   int32(weight),
	})
	if err != nil {
		return err
	}
	// Print the updated pool so the user can confirm the new weight.
	for _, pool := range info.Pools {
		if pool.Name != poolName {
			continue
		}
		for _, pb := range pool.Backends {
			if pb.Name == backendName {
				fmt.Printf("%s pool %s backend %s: weight set to %d\n", info.Name, pool.Name, pb.Name, pb.Weight)
				return nil
			}
		}
	}
	return nil
}

func runEnableBackend(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: set backend <name> enable")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.EnableBackend(ctx, &grpcapi.BackendRequest{Name: args[0]})
	if err != nil {
		return err
	}
	fmt.Printf("%s: enabled, state is '%s'\n", info.Name, info.State)
	return nil
}

func runDisableBackend(ctx context.Context, client grpcapi.MaglevClient, args []string) error {
	if len(args) == 0 {
		return fmt.Errorf("usage: set backend <name> disable")
	}
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	info, err := client.DisableBackend(ctx, &grpcapi.BackendRequest{Name: args[0]})
	if err != nil {
		return err
	}
	fmt.Printf("%s: disabled, state is '%s'\n", info.Name, info.State)
	return nil
}

func runConfigCheck(ctx context.Context, client grpcapi.MaglevClient, _ []string) error {
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	resp, err := client.CheckConfig(ctx, &grpcapi.CheckConfigRequest{})
	if err != nil {
		return err
	}
	if resp.Ok {
		fmt.Println("config ok")
		return nil
	}
	if resp.ParseError != "" {
		return fmt.Errorf("parse error: %s", resp.ParseError)
	}
	return fmt.Errorf("semantic error: %s", resp.SemanticError)
}

func runConfigReload(ctx context.Context, client grpcapi.MaglevClient, _ []string) error {
	ctx, cancel := context.WithTimeout(ctx, callTimeout)
	defer cancel()
	resp, err := client.ReloadConfig(ctx, &grpcapi.ReloadConfigRequest{})
	if err != nil {
		return err
	}
	if resp.Ok {
		fmt.Println("config reloaded")
		return nil
	}
	if resp.ParseError != "" {
		return fmt.Errorf("parse error: %s", resp.ParseError)
	}
	if resp.SemanticError != "" {
		return fmt.Errorf("semantic error: %s", resp.SemanticError)
	}
	return fmt.Errorf("reload error: %s", resp.ReloadError)
}

// formatDuration formats a duration as Xd Xh Xm Xs without milliseconds.
func formatDuration(d time.Duration) string {
	if d < 0 {
		d = 0
	}
	d = d.Truncate(time.Second)

	days := int(d.Hours()) / 24
	d -= time.Duration(days) * 24 * time.Hour
	hours := int(d.Hours())
	d -= time.Duration(hours) * time.Hour
	minutes := int(d.Minutes())
	d -= time.Duration(minutes) * time.Minute
	seconds := int(d.Seconds())

	var b strings.Builder
	if days > 0 {
		fmt.Fprintf(&b, "%dd", days)
	}
	if hours > 0 {
		fmt.Fprintf(&b, "%dh", hours)
	}
	if minutes > 0 {
		fmt.Fprintf(&b, "%dm", minutes)
	}
	if seconds > 0 || b.Len() == 0 {
		fmt.Fprintf(&b, "%ds", seconds)
	}
	return b.String()
}

func formatAgo(d time.Duration) string {
	return formatDuration(d) + " ago"
}