Add disk space reporting to runner capabilities

- Add DiskInfo struct with total, free, used bytes and usage percentage
- Detect disk space using unix.Statfs on startup
- Add periodic capabilities updates every 5 minutes
- Add disk space warnings at 85% (warning) and 95% (critical) thresholds
- Send updated capabilities to Gitea server periodically

This helps monitor runners that are running low on disk space.

Co-Authored-By: Claude <noreply@anthropic.com>

internal/app/cmd/daemon.go

@@ -30,6 +30,15 @@ import (
 	"gitea.com/gitea/act_runner/internal/pkg/ver"
 )
 
+const (
+	// DiskSpaceWarningThreshold is the percentage at which to warn about low disk space
+	DiskSpaceWarningThreshold = 85.0
+	// DiskSpaceCriticalThreshold is the percentage at which to log critical warnings
+	DiskSpaceCriticalThreshold = 95.0
+	// CapabilitiesUpdateInterval is how often to update capabilities (including disk space)
+	CapabilitiesUpdateInterval = 5 * time.Minute
+)
+
 func runDaemon(ctx context.Context, daemArgs *daemonArgs, configFile *string) func(cmd *cobra.Command, args []string) error {
 	return func(cmd *cobra.Command, args []string) error {
 		cfg, err := config.LoadDefault(*configFile)
@@ -147,6 +156,9 @@ func runDaemon(ctx context.Context, daemArgs *daemonArgs, configFile *string) fu
 		capabilitiesJson := capabilities.ToJSON()
 		log.Infof("detected capabilities: %s", capabilitiesJson)
 
+		// Check disk space and warn if low
+		checkDiskSpaceWarnings(capabilities)
+
 		// declare the labels of the runner before fetching tasks
 		resp, err := runner.Declare(ctx, ls.Names(), capabilitiesJson)
 		if err != nil && connect.CodeOf(err) == connect.CodeUnimplemented {
@@ -160,6 +172,9 @@ func runDaemon(ctx context.Context, daemArgs *daemonArgs, configFile *string) fu
 				resp.Msg.Runner.Name, resp.Msg.Runner.Version, resp.Msg.Runner.Labels)
 		}
 
+		// Start periodic capabilities update goroutine
+		go periodicCapabilitiesUpdate(ctx, runner, ls.Names(), dockerHost)
+
 		poller := poll.New(cfg, cli, runner)
 
 		if daemArgs.Once || reg.Ephemeral {
@@ -194,6 +209,53 @@ func runDaemon(ctx context.Context, daemArgs *daemonArgs, configFile *string) fu
 	}
 }
 
+// checkDiskSpaceWarnings logs warnings if disk space is low
+func checkDiskSpaceWarnings(capabilities *envcheck.RunnerCapabilities) {
+	if capabilities.Disk == nil {
+		return
+	}
+
+	usedPercent := capabilities.Disk.UsedPercent
+	freeGB := float64(capabilities.Disk.Free) / (1024 * 1024 * 1024)
+
+	if usedPercent >= DiskSpaceCriticalThreshold {
+		log.Errorf("CRITICAL: Disk space critically low! %.1f%% used, only %.2f GB free. Runner may fail to execute jobs!", usedPercent, freeGB)
+	} else if usedPercent >= DiskSpaceWarningThreshold {
+		log.Warnf("WARNING: Disk space running low. %.1f%% used, %.2f GB free. Consider cleaning up disk space.", usedPercent, freeGB)
+	}
+}
+
+// periodicCapabilitiesUpdate periodically updates capabilities including disk space
+func periodicCapabilitiesUpdate(ctx context.Context, runner *run.Runner, labelNames []string, dockerHost string) {
+	ticker := time.NewTicker(CapabilitiesUpdateInterval)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ctx.Done():
+			log.Debug("stopping periodic capabilities update")
+			return
+		case <-ticker.C:
+			// Detect updated capabilities (disk space changes over time)
+			capabilities := envcheck.DetectCapabilities(ctx, dockerHost)
+			capabilitiesJson := capabilities.ToJSON()
+
+			// Check for disk space warnings
+			checkDiskSpaceWarnings(capabilities)
+
+			// Send updated capabilities to server
+			_, err := runner.Declare(ctx, labelNames, capabilitiesJson)
+			if err != nil {
+				log.WithError(err).Debug("failed to update capabilities")
+			} else {
+				log.Debugf("capabilities updated: disk %.1f%% used, %.2f GB free",
+					capabilities.Disk.UsedPercent,
+					float64(capabilities.Disk.Free)/(1024*1024*1024))
+			}
+		}
+	}
+}
+
 type daemonArgs struct {
 	Once bool
 }

internal/pkg/envcheck/capabilities.go

@@ -12,8 +12,17 @@ import (
 	"time"
 
 	"github.com/docker/docker/client"
+	"golang.org/x/sys/unix"
 )
 
+// DiskInfo holds disk space information
+type DiskInfo struct {
+	Total       uint64  `json:"total_bytes"`
+	Free        uint64  `json:"free_bytes"`
+	Used        uint64  `json:"used_bytes"`
+	UsedPercent float64 `json:"used_percent"`
+}
+
 // RunnerCapabilities represents the capabilities of a runner for AI consumption
 type RunnerCapabilities struct {
 	OS               string              `json:"os"`
@@ -25,6 +34,7 @@ type RunnerCapabilities struct {
 	Tools            map[string][]string `json:"tools,omitempty"`
 	Features         *CapabilityFeatures `json:"features,omitempty"`
 	Limitations      []string            `json:"limitations,omitempty"`
+	Disk             *DiskInfo           `json:"disk,omitempty"`
 }
 
 // CapabilityFeatures represents feature support flags
@@ -64,9 +74,40 @@ func DetectCapabilities(ctx context.Context, dockerHost string) *RunnerCapabilit
 	// Detect common tools
 	detectTools(ctx, cap)
 
+	// Detect disk space
+	cap.Disk = detectDiskSpace()
+
 	return cap
 }
 
+// detectDiskSpace detects disk space on the root filesystem
+func detectDiskSpace() *DiskInfo {
+	var stat unix.Statfs_t
+
+	// Get stats for root filesystem (or current working directory)
+	path := "/"
+	if runtime.GOOS == "windows" {
+		path = "C:\\"
+	}
+
+	err := unix.Statfs(path, &stat)
+	if err != nil {
+		return nil
+	}
+
+	total := stat.Blocks * uint64(stat.Bsize)
+	free := stat.Bavail * uint64(stat.Bsize)
+	used := total - free
+	usedPercent := float64(used) / float64(total) * 100
+
+	return &DiskInfo{
+		Total:       total,
+		Free:        free,
+		Used:        used,
+		UsedPercent: usedPercent,
+	}
+}
+
 // ToJSON converts capabilities to JSON string for transmission
 func (c *RunnerCapabilities) ToJSON() string {
 	data, err := json.Marshal(c)