Add a way to trigger immediate backups

Send SIGUSR1 to the agent binary.

README.md

@@ -252,6 +252,10 @@ and this dataset source:
     - name: db2
 ```
 
+## Runtime signals
+
+The agent will reload its configuration on SIGHUP, and it will
+immediately trigger all backup jobs upon receiving SIGUSR1.
 
 # TODO
 

agent.go

@@ -95,3 +95,8 @@ func makeSchedule(ctx context.Context, m Manager, sourceSpecs []SourceSpec, host
 
 	return sched, merr.OrNil()
 }
+
+// RunNow starts all jobs right now, regardless of their schedule.
+func (a *Agent) RunNow() {
+	a.sched.RunNow()
+}

cmd/tabacco/agent.go

@@ -72,12 +72,23 @@ func (c *agentCommand) Execute(ctx context.Context, f *flag.FlagSet, args ...int
 		return subcommands.ExitFailure
 	}
 
+	// Build the Agent, and hook SIGUSR1 so that it triggers all
+	// the backup jobs immediately (useful for emergencies or
+	// debugging purposes).
 	agent, err := tabacco.NewAgent(ctx, configMgr, store)
 	if err != nil {
 		log.Printf("error: %v", err)
 		return subcommands.ExitFailure
 	}
 	defer agent.Close() // nolint
+	usr1Ch := make(chan os.Signal, 1)
+	go func() {
+		for range usr1Ch {
+			log.Printf("SIGUSR1 received, starting all jobs immediately")
+			agent.RunNow()
+		}
+	}()
+	signal.Notify(usr1Ch, syscall.SIGUSR1)
 
 	log.Printf("backup agent started")
 

jobs/scheduler.go

@@ -194,6 +194,21 @@ func (s *Scheduler) Stop() {
 	close(s.notifyCh)
 }
 
+// RunNow starts all jobs right now, regardless of their schedule.
+func (s *Scheduler) RunNow() {
+	s.mx.Lock()
+	defer s.mx.Unlock()
+	if s.cur == nil {
+		return
+	}
+
+	for _, entry := range s.cur.c.Entries() {
+		go func(entry *cron.Entry) {
+			entry.Job.Run()
+		}(entry)
+	}
+}
+
 // CronJobStatus represents the status of a job, either scheduled,
 // running, or terminated in the past.
 type CronJobStatus struct {