feat: add log.job.dir (#1165)

`log.job.dir` makes the runner write a copy of every task's log to that directory, as `<start time>-task-<id>.log`: the rows exactly as Gitea received them, with the same masking and the job's result on the last line. Off by default, and what Gitea shows does not change.

`log.job.retention` (default `168h`) and `log.job.max_size` (default `1GB`) bound the directory. Documented in the README.

---------

Co-authored-by: silverwind <me@silverwind.io>
Reviewed-on: https://gitea.com/gitea/runner/pulls/1165
Reviewed-by: silverwind <2021+silverwind@noreply.gitea.com>

internal/pkg/config/config.example.yaml

@@ -1,13 +1,20 @@
 # Every option with its default value, all commented out. Read this file, do not copy it.
 # `./gitea-runner config init` writes a config file to copy the lines you change into.
 
-# Logging for the runner process itself (messages printed to stderr).
-# This does not control how workflow step output is streamed to the Gitea UI;
-# tune that with runner.log_report_* below.
+# Logging for the runner process itself (messages printed to stderr), plus the copy of
+# each task's log kept under log.job. Neither controls how workflow step output is streamed
+# to the Gitea UI; tune that with runner.log_report_* below.
 log:
   # logrus severity: trace, debug, info, warn, error, fatal, panic.
   # trace and debug turn on caller/file:line in log lines. Default if omitted: info.
   #level: info
+  # Write a copy of each task's log to dir as <start time>-task-<id>.log, so a job's output
+  # survives a failure to send it to Gitea. A path turns them on, empty turns them off.
+  # retention is how long a log is kept (0s keeps all), max_size caps one log (0 is no limit).
+  #job:
+  #  dir: ""
+  #  retention: 168h
+  #  max_size: 1GB
 
 runner:
   # Where to store the registration result.

internal/pkg/config/config.go

@@ -38,9 +38,17 @@ const Minimal = `# Minimal config file. Every option it does not set keeps its d
 # "gitea-runner config generate" prints all options, "config set <key> <value>" sets one here.
 `
 
-// Log represents the configuration for logging.
+// Log represents the runner process's own logging, plus the copy of each task's log it keeps.
 type Log struct {
 	Level string `yaml:"level"` // Level indicates the logging level.
+	Job   LogJob `yaml:"job"`   // Job configures the copy of each task's log kept on the runner host.
+}
+
+// LogJob represents the configuration for the copy of each task's log kept on the runner host.
+type LogJob struct {
+	Dir       string        `yaml:"dir"`       // Dir is the directory the runner writes each task's log to. Empty, the default, writes none.
+	Retention time.Duration `yaml:"retention"` // Retention deletes a task's log directory once it is older than this. Default 168h, 0s keeps them regardless of age.
+	MaxSize   Size          `yaml:"max_size"`  // MaxSize caps one task's log file. Default 1GB, 0 is no limit.
 }
 
 // Runner represents the configuration for the runner.
@@ -202,7 +210,8 @@ type Config struct {
 // LoadDefault returns the default configuration.
 // If file is not empty, it will be used to load the configuration.
 func LoadDefault(file string) (*Config, error) {
-	cfg := &Config{Cache: DefaultCache()}
+	// Seeded before the file is read, so a written 0 can mean off.
+	cfg := &Config{Cache: DefaultCache(), Log: Log{Job: LogJob{Retention: 7 * 24 * time.Hour, MaxSize: 1024 * 1024 * 1024}}}
 	definedRunnerKeys := map[string]bool{}
 	if file != "" {
 		content, err := os.ReadFile(file)

internal/pkg/config/config_test.go

@@ -186,14 +186,14 @@ runner:
 	assert.Equal(t, 5*time.Minute, cfg.Runner.PostTaskScriptTimeout)
 }
 
-func TestLoadDefault_LoadsCacheEviction(t *testing.T) {
-	write := func(t *testing.T, body string) string {
-		t.Helper()
-		path := filepath.Join(t.TempDir(), "config.yaml")
-		require.NoError(t, os.WriteFile(path, []byte(body), 0o600))
-		return path
-	}
+func write(t *testing.T, body string) string {
+	t.Helper()
+	path := filepath.Join(t.TempDir(), "config.yaml")
+	require.NoError(t, os.WriteFile(path, []byte(body), 0o600))
+	return path
+}
 
+func TestLoadDefault_LoadsCacheEviction(t *testing.T) {
 	t.Run("sizes accept any spelling of the unit", func(t *testing.T) {
 		cfg, err := LoadDefault(write(t, "cache:\n  retention: 336h\n  repo_size_limit: 50gb\n  size_limit: 1TiB\n  sweep_interval: 15m\n"))
 		require.NoError(t, err)
@@ -217,6 +217,14 @@ func TestLoadDefault_LoadsCacheEviction(t *testing.T) {
 	})
 }
 
+func TestLoadDefault_LoadsJobLogs(t *testing.T) {
+	cfg, err := LoadDefault(write(t, "log:\n  job:\n    dir: /var/log/jobs\n    retention: 0s\n    max_size: 100MB\n"))
+	require.NoError(t, err)
+	assert.Equal(t, "/var/log/jobs", cfg.Log.Job.Dir)
+	assert.Zero(t, cfg.Log.Job.Retention, "zero keeps every task directory")
+	assert.Equal(t, Size(100*1024*1024), cfg.Log.Job.MaxSize)
+}
+
 func TestLoadDefault_LoadsJobHooks(t *testing.T) {
 	dir := t.TempDir()
 	path := filepath.Join(dir, "config.yaml")