feat(cli): add logs cmd (#21430)

This PR adds a command to view the provisioner and agent logs for a
given workspace.
Note: I did investigate using the existing `cliui` methods to tail the
logs but they are tailored to a very specific use-case.

Other changes:
- Adds `Agents` to `dbfake.WorkspaceResponse`
- Adds methods to generate provisioner and agent logs in `dbgen`

---------

Co-authored-by: Steven Masley <Emyrk@users.noreply.github.com>

cli/logs.go

@@ -0,0 +1,270 @@
+package cli
+
+import (
+	"context"
+	"fmt"
+	"slices"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/coder/coder/v2/cli/cliui"
+	"github.com/coder/coder/v2/codersdk"
+	"github.com/coder/serpent"
+
+	"github.com/google/uuid"
+	"golang.org/x/sync/errgroup"
+	"golang.org/x/xerrors"
+)
+
+func (r *RootCmd) logs() *serpent.Command {
+	var (
+		buildNumberArg int64
+		followArg      bool
+	)
+	cmd := &serpent.Command{
+		Use:   "logs <workspace>",
+		Short: "View logs for a workspace",
+		Long:  "View logs for a workspace",
+		Middleware: serpent.Chain(
+			serpent.RequireNArgs(1),
+		),
+		Options: serpent.OptionSet{
+			{
+				Name:          "Build Number",
+				Flag:          "build-number",
+				FlagShorthand: "n",
+				Description:   "Only show logs for a specific build number. Defaults to 0, which maps to the most recent build (build numbers start at 1). Negative values are treated as offsets—for example, -1 refers to the previous build.",
+				Value:         serpent.Int64Of(&buildNumberArg),
+				Default:       "0",
+			},
+			{
+				Name:          "Follow",
+				Flag:          "follow",
+				FlagShorthand: "f",
+				Description:   "Follow logs as they are emitted.",
+				Value:         serpent.BoolOf(&followArg),
+				Default:       "false",
+			},
+		},
+		Handler: func(inv *serpent.Invocation) error {
+			ctx := inv.Context()
+			client, err := r.InitClient(inv)
+			if err != nil {
+				return err
+			}
+			ws, err := namedWorkspace(inv.Context(), client, inv.Args[0])
+			if err != nil {
+				return xerrors.Errorf("failed to get workspace: %w", err)
+			}
+			bld := ws.LatestBuild
+			buildNumber := buildNumberArg
+
+			// User supplied a negative build number, treat it as an offset from the latest build
+			if buildNumber < 0 {
+				buildNumber = int64(ws.LatestBuild.BuildNumber) + buildNumberArg
+				if buildNumber < 1 {
+					return xerrors.Errorf("invalid build number offset: %d latest build number: %d", buildNumberArg, ws.LatestBuild.BuildNumber)
+				}
+			}
+
+			// Fetch specific build if requested
+			if buildNumber > 0 {
+				wb, err := client.WorkspaceBuildByUsernameAndWorkspaceNameAndBuildNumber(ctx, ws.OwnerName, ws.Name, strconv.FormatInt(buildNumber, 10))
+				if err != nil {
+					return xerrors.Errorf("failed to get build %d: %w", buildNumberArg, err)
+				}
+				bld = wb
+			}
+			cliui.Infof(inv.Stdout, "--- Logs for workspace build #%d (ID: %s Template Version: %s) ---", bld.BuildNumber, bld.ID, bld.TemplateVersionName)
+			logs, logsCh, err := workspaceLogs(ctx, client, bld, followArg)
+			if err != nil {
+				return err
+			}
+			for _, log := range logs {
+				_, _ = fmt.Fprintln(inv.Stdout, log.String())
+			}
+			if followArg {
+				_, _ = fmt.Fprintln(inv.Stdout, "--- Streaming logs ---")
+				for log := range logsCh {
+					_, _ = fmt.Fprintln(inv.Stdout, log.String())
+				}
+			}
+			return nil
+		},
+	}
+	return cmd
+}
+
+type logLine struct {
+	ts      time.Time
+	Content string
+}
+
+func (l *logLine) String() string {
+	var sb strings.Builder
+	_, _ = sb.WriteString(l.ts.Format(time.RFC3339))
+	_, _ = sb.WriteString(l.Content)
+	return sb.String()
+}
+
+// workspaceLogs fetches logs for the given workspace build. If follow is true,
+// the returned channel will stream new logs as they are emitted. Otherwise,
+// the channel will be closed immediately.
+// nolint: revive // control flag is appropriate here
+func workspaceLogs(ctx context.Context, client *codersdk.Client, wb codersdk.WorkspaceBuild, follow bool) ([]logLine, <-chan logLine, error) {
+	logs := make([]logLine, 0)
+	logsCh := make(chan logLine)
+	followCh := make(chan logLine)
+
+	var fetchGroup, followGroup errgroup.Group
+
+	buildLogsAfterCh := make(chan int64)
+	fetchGroup.Go(func() error {
+		var afterID int64
+		defer func() {
+			if !follow {
+				return
+			}
+			buildLogsAfterCh <- afterID
+		}()
+		buildLogsC, closer, err := client.WorkspaceBuildLogsAfter(ctx, wb.ID, 0)
+		if err != nil {
+			return xerrors.Errorf("failed to get build logs: %w", err)
+		}
+		defer closer.Close()
+		for log := range buildLogsC {
+			afterID = log.ID
+			logsCh <- logLine{
+				ts:      log.CreatedAt,
+				Content: buildLogToString(log),
+			}
+		}
+		return nil
+	})
+
+	if follow {
+		followGroup.Go(func() error {
+			afterID := <-buildLogsAfterCh
+			buildLogsC, closer, err := client.WorkspaceBuildLogsAfter(ctx, wb.ID, afterID)
+			if err != nil {
+				return xerrors.Errorf("failed to follow build logs: %w", err)
+			}
+			defer closer.Close()
+			for log := range buildLogsC {
+				followCh <- logLine{
+					ts:      log.CreatedAt,
+					Content: buildLogToString(log),
+				}
+			}
+			return nil
+		})
+	}
+
+	for _, res := range wb.Resources {
+		for _, agt := range res.Agents {
+			logSrcNames := make(map[uuid.UUID]string)
+			for _, src := range agt.LogSources {
+				logSrcNames[src.ID] = src.DisplayName
+			}
+			agentLogsAfterCh := make(chan int64)
+			var afterID int64
+			fetchGroup.Go(func() error {
+				defer func() {
+					if !follow {
+						return
+					}
+					agentLogsAfterCh <- afterID
+				}()
+				agentLogsCh, closer, err := client.WorkspaceAgentLogsAfter(ctx, agt.ID, 0, false)
+				if err != nil {
+					return xerrors.Errorf("failed to get agent logs: %w", err)
+				}
+				defer closer.Close()
+				for logChunk := range agentLogsCh {
+					for _, log := range logChunk {
+						afterID = log.ID
+						logsCh <- logLine{
+							ts:      log.CreatedAt,
+							Content: workspaceAgentLogToString(log, agt.Name, logSrcNames[log.SourceID]),
+						}
+					}
+				}
+				return nil
+			})
+
+			if follow {
+				followGroup.Go(func() error {
+					afterID := <-agentLogsAfterCh
+					agentLogsCh, closer, err := client.WorkspaceAgentLogsAfter(ctx, agt.ID, afterID, true)
+					if err != nil {
+						return xerrors.Errorf("failed to follow agent logs: %w", err)
+					}
+					defer closer.Close()
+					for logChunk := range agentLogsCh {
+						for _, log := range logChunk {
+							followCh <- logLine{
+								ts:      log.CreatedAt,
+								Content: workspaceAgentLogToString(log, agt.Name, logSrcNames[log.SourceID]),
+							}
+						}
+					}
+					return nil
+				})
+			}
+		}
+	}
+
+	logsDone := make(chan struct{})
+	go func() {
+		defer close(logsDone)
+		for log := range logsCh {
+			logs = append(logs, log)
+		}
+	}()
+
+	err := fetchGroup.Wait()
+	close(logsCh)
+	<-logsDone
+
+	slices.SortFunc(logs, func(a, b logLine) int {
+		return a.ts.Compare(b.ts)
+	})
+
+	if follow {
+		go func() {
+			_ = followGroup.Wait()
+			close(followCh)
+		}()
+	} else {
+		close(followCh)
+	}
+
+	return logs, followCh, err
+}
+
+func buildLogToString(log codersdk.ProvisionerJobLog) string {
+	var sb strings.Builder
+	_, _ = sb.WriteString(" [")
+	_, _ = sb.WriteString(string(log.Level))
+	_, _ = sb.WriteString("] [")
+	_, _ = sb.WriteString("provisioner|")
+	_, _ = sb.WriteString(log.Stage)
+	_, _ = sb.WriteString("] ")
+	_, _ = sb.WriteString(log.Output)
+	return sb.String()
+}
+
+func workspaceAgentLogToString(log codersdk.WorkspaceAgentLog, agtName, srcName string) string {
+	var sb strings.Builder
+	_, _ = sb.WriteString(" [")
+	_, _ = sb.WriteString(string(log.Level))
+	_, _ = sb.WriteString("] [")
+	_, _ = sb.WriteString("agent.")
+	_, _ = sb.WriteString(agtName)
+	_, _ = sb.WriteString("|")
+	_, _ = sb.WriteString(srcName)
+	_, _ = sb.WriteString("] ")
+	_, _ = sb.WriteString(log.Output)
+	return sb.String()
+}