runner/seed, app/service: seed run-time stats from log files (T2.5)

Add SeedStats, which reconstructs per-job execution-time aggregates from
existing log files: suffix-matched by sanitized job name, bounded by
MaxLogFiles, and tolerant of duration-less legacy logs (counted in
run/fail totals but excluded from last/avg/max). NewService folds the
seed into each JobRuntime at build time so stats survive a restart.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/runner/seed.go

@@ -0,0 +1,140 @@
+package runner
+
+import (
+	"bufio"
+	"os"
+	"path/filepath"
+	"sort"
+	"strconv"
+	"strings"
+
+	"gitea.mixdep.ru/mix/gosentry/src/domain"
+)
+
+// SeededStats are the aggregate execution-time statistics reconstructed from a
+// job's existing log files at startup. The fields mirror the run-time counters
+// on domain.JobRuntime so the caller can fold them in directly.
+type SeededStats struct {
+	RunCount       int
+	FailCount      int
+	LastDurationMS int64
+	AvgDurationMS  int64
+	MaxDurationMS  int64
+}
+
+// SeedStats scans logsDir once and reconstructs per-job execution-time
+// statistics from the log files written by previous runs, keyed by Job.ID.
+//
+// Log files are matched to a job by the sanitized job-name suffix of the file
+// name (the same name writeRunLog uses), so no per-file header read is needed to
+// associate a log with its job. For each job only the newest maxFiles matching
+// logs are parsed, mirroring the retention policy that CleanupLogs enforces; a
+// maxFiles of zero or less means "no bound". The duration and state are read
+// from each log's header. Logs written before duration tracking existed carry no
+// duration line: those are tolerated — they still count toward RunCount and
+// FailCount but are left out of the duration aggregates (last/avg/max) so a
+// missing duration cannot masquerade as a zero-millisecond run.
+//
+// A missing or unreadable logs directory yields an empty map rather than an
+// error: seeding is best-effort and must never block startup.
+func SeedStats(logsDir string, jobs []domain.Job, maxFiles int) map[int]SeededStats {
+	result := make(map[int]SeededStats, len(jobs))
+	entries, err := os.ReadDir(logsDir)
+	if err != nil {
+		return result
+	}
+
+	// Group log file names by the sanitized job-name portion of the file name.
+	// File names are "<timestamp>_<sanitizedName>.log"; the timestamp has no
+	// underscore, so everything after the first underscore is the name part.
+	byName := make(map[string][]string)
+	for _, entry := range entries {
+		if entry.IsDir() {
+			continue
+		}
+		name := entry.Name()
+		if !strings.HasSuffix(strings.ToLower(name), ".log") {
+			continue
+		}
+		base := name[:len(name)-len(".log")]
+		idx := strings.Index(base, "_")
+		if idx < 0 {
+			continue
+		}
+		jobPart := base[idx+1:]
+		byName[jobPart] = append(byName[jobPart], name)
+	}
+
+	for _, job := range jobs {
+		files := byName[sanitizeFileName(job.Name)]
+		if len(files) == 0 {
+			continue
+		}
+		// The timestamp prefix sorts chronologically, so a lexical sort puts the
+		// oldest first; keep the newest maxFiles to honor the retention bound.
+		sort.Strings(files)
+		if maxFiles > 0 && len(files) > maxFiles {
+			files = files[len(files)-maxFiles:]
+		}
+		result[job.ID] = aggregateLogStats(logsDir, files)
+	}
+	return result
+}
+
+// aggregateLogStats folds the header of each log file (oldest first) into one
+// SeededStats. Files lacking a duration line contribute to the run/fail counts
+// but not to the duration aggregates.
+func aggregateLogStats(logsDir string, files []string) SeededStats {
+	var stats SeededStats
+	var durationSum int64
+	var durationCount int
+	for _, file := range files {
+		state, durationMS, hasDuration := readLogHeader(filepath.Join(logsDir, file))
+		stats.RunCount++
+		if state == "Failed" {
+			stats.FailCount++
+		}
+		if hasDuration {
+			// Files are oldest first, so the last assignment is the newest run.
+			stats.LastDurationMS = durationMS
+			if durationMS > stats.MaxDurationMS {
+				stats.MaxDurationMS = durationMS
+			}
+			durationSum += durationMS
+			durationCount++
+		}
+	}
+	if durationCount > 0 {
+		stats.AvgDurationMS = durationSum / int64(durationCount)
+	}
+	return stats
+}
+
+// readLogHeader reads the "state" and "duration" fields from a log file's
+// header (the lines before the first blank line). hasDuration reports whether a
+// well-formed duration line was present, distinguishing a legacy duration-less
+// log from one that genuinely recorded a zero-millisecond run.
+func readLogHeader(path string) (state string, durationMS int64, hasDuration bool) {
+	file, err := os.Open(path)
+	if err != nil {
+		return "", 0, false
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if line == "" {
+			break // end of header
+		}
+		if rest, ok := strings.CutPrefix(line, "state: "); ok {
+			state = strings.TrimSpace(rest)
+		} else if rest, ok := strings.CutPrefix(line, "duration: "); ok {
+			if value, err := strconv.ParseInt(strings.TrimSpace(rest), 10, 64); err == nil {
+				durationMS = value
+				hasDuration = true
+			}
+		}
+	}
+	return state, durationMS, hasDuration
+}