add support for SIGUSR1 to trigger flush (#7366)

agent/agent.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"log"
+	"os"
 	"runtime"
 	"sync"
 	"time"
@@ -516,16 +517,7 @@ func (a *Agent) runOutputs(
 		wg.Add(1)
 		go func(output *models.RunningOutput) {
 			defer wg.Done()
-
-			if a.Config.Agent.RoundInterval {
-				err := internal.SleepContext(
-					ctx, internal.AlignDuration(startTime, interval))
-				if err != nil {
-					return
-				}
-			}
-
-			a.flush(ctx, output, interval, jitter)
+			a.flushLoop(ctx, startTime, output, interval, jitter)
 		}(output)
 	}
 
@@ -546,25 +538,39 @@ func (a *Agent) runOutputs(
 	return nil
 }
 
-// flush runs an output's flush function periodically until the context is
+// flushLoop runs an output's flush function periodically until the context is
 // done.
-func (a *Agent) flush(
+func (a *Agent) flushLoop(
 	ctx context.Context,
+	startTime time.Time,
 	output *models.RunningOutput,
 	interval time.Duration,
 	jitter time.Duration,
 ) {
-	// since we are watching two channels we need a ticker with the jitter
-	// integrated.
-	ticker := NewTicker(interval, jitter)
-	defer ticker.Stop()
-
 	logError := func(err error) {
 		if err != nil {
 			log.Printf("E! [agent] Error writing to %s: %v", output.LogName(), err)
 		}
 	}
 
+	// watch for flush requests
+	flushRequested := make(chan os.Signal, 1)
+	watchForFlushSignal(flushRequested)
+
+	// align to round interval
+	if a.Config.Agent.RoundInterval {
+		err := internal.SleepContext(
+			ctx, internal.AlignDuration(startTime, interval))
+		if err != nil {
+			return
+		}
+	}
+
+	// since we are watching two channels we need a ticker with the jitter
+	// integrated.
+	ticker := NewTicker(interval, jitter)
+	defer ticker.Stop()
+
 	for {
 		// Favor shutdown over other methods.
 		select {
@@ -575,8 +581,13 @@ func (a *Agent) flush(
 		}
 
 		select {
+		case <-ctx.Done():
+			logError(a.flushOnce(output, interval, output.Write))
+			return
 		case <-ticker.C:
 			logError(a.flushOnce(output, interval, output.Write))
+		case <-flushRequested:
+			logError(a.flushOnce(output, interval, output.Write))
 		case <-output.BatchReady:
 			// Favor the ticker over batch ready
 			select {
@@ -585,9 +596,6 @@ func (a *Agent) flush(
 			default:
 				logError(a.flushOnce(output, interval, output.WriteBatch))
 			}
-		case <-ctx.Done():
-			logError(a.flushOnce(output, interval, output.Write))
-			return
 		}
 	}
 }

agent/agent_notwindows.go

@@ -0,0 +1,16 @@
+// +build !windows
+
+package agent
+
+import (
+	"os"
+	"os/signal"
+	"syscall"
+)
+
+const flushSignal = syscall.SIGUSR1
+
+func watchForFlushSignal(flushRequested chan os.Signal) {
+	signal.Notify(flushRequested, flushSignal)
+	defer signal.Stop(flushRequested)
+}

agent/agent_windows.go

@@ -0,0 +1,9 @@
+// +build windows
+
+package agent
+
+import "os"
+
+func watchForFlushSignal(flushRequested chan os.Signal) {
+	// not implemented
+}

cmd/telegraf/telegraf.go

@@ -10,7 +10,6 @@ import (
 	_ "net/http/pprof" // Comment this line to disable pprof endpoint.
 	"os"
 	"os/signal"
-	"runtime"
 	"sort"
 	"strings"
 	"syscall"
@@ -27,16 +26,16 @@ import (
 	"github.com/influxdata/telegraf/plugins/outputs"
 	_ "github.com/influxdata/telegraf/plugins/outputs/all"
 	_ "github.com/influxdata/telegraf/plugins/processors/all"
-	"github.com/kardianos/service"
 )
 
+// If you update these, update usage.go and usage_windows.go
 var fDebug = flag.Bool("debug", false,
 	"turn on debug logging")
 var pprofAddr = flag.String("pprof-addr", "",
 	"pprof address to listen on, not activate pprof if empty")
 var fQuiet = flag.Bool("quiet", false,
 	"run in quiet mode")
-var fTest = flag.Bool("test", false, "enable test mode: gather metrics, print them out, and exit")
+var fTest = flag.Bool("test", false, "enable test mode: gather metrics, print them out, and exit. Note: Test mode only runs inputs, not processors, aggregators, or outputs")
 var fTestWait = flag.Int("test-wait", 0, "wait up to this many seconds for service inputs to complete in test mode")
 var fConfig = flag.String("config", "", "configuration file to load")
 var fConfigDirectory = flag.String("config-directory", "",
@@ -78,7 +77,6 @@ var (
 var stop chan struct{}
 
 func reloadLoop(
-	stop chan struct{},
 	inputFilters []string,
 	outputFilters []string,
 	aggregatorFilters []string,
@@ -91,7 +89,7 @@ func reloadLoop(
 
 		ctx, cancel := context.WithCancel(context.Background())
 
-		signals := make(chan os.Signal)
+		signals := make(chan os.Signal, 1)
 		signal.Notify(signals, os.Interrupt, syscall.SIGHUP,
 			syscall.SIGTERM, syscall.SIGINT)
 		go func() {
@@ -208,32 +206,6 @@ func usageExit(rc int) {
 	os.Exit(rc)
 }
 
-type program struct {
-	inputFilters      []string
-	outputFilters     []string
-	aggregatorFilters []string
-	processorFilters  []string
-}
-
-func (p *program) Start(s service.Service) error {
-	go p.run()
-	return nil
-}
-func (p *program) run() {
-	stop = make(chan struct{})
-	reloadLoop(
-		stop,
-		p.inputFilters,
-		p.outputFilters,
-		p.aggregatorFilters,
-		p.processorFilters,
-	)
-}
-func (p *program) Stop(s service.Service) error {
-	close(stop)
-	return nil
-}
-
 func formatFullVersion() string {
 	var parts = []string{"Telegraf"}
 
@@ -380,80 +352,10 @@ func main() {
 		log.Println("Telegraf version already configured to: " + internal.Version())
 	}
 
-	if runtime.GOOS == "windows" && windowsRunAsService() {
-		programFiles := os.Getenv("ProgramFiles")
-		if programFiles == "" { // Should never happen
-			programFiles = "C:\\Program Files"
-		}
-		svcConfig := &service.Config{
-			Name:        *fServiceName,
-			DisplayName: *fServiceDisplayName,
-			Description: "Collects data using a series of plugins and publishes it to" +
-				"another series of plugins.",
-			Arguments: []string{"--config", programFiles + "\\Telegraf\\telegraf.conf"},
-		}
-
-		prg := &program{
-			inputFilters:      inputFilters,
-			outputFilters:     outputFilters,
-			aggregatorFilters: aggregatorFilters,
-			processorFilters:  processorFilters,
-		}
-		s, err := service.New(prg, svcConfig)
-		if err != nil {
-			log.Fatal("E! " + err.Error())
-		}
-		// Handle the --service flag here to prevent any issues with tooling that
-		// may not have an interactive session, e.g. installing from Ansible.
-		if *fService != "" {
-			if *fConfig != "" {
-				svcConfig.Arguments = []string{"--config", *fConfig}
-			}
-			if *fConfigDirectory != "" {
-				svcConfig.Arguments = append(svcConfig.Arguments, "--config-directory", *fConfigDirectory)
-			}
-			//set servicename to service cmd line, to have a custom name after relaunch as a service
-			svcConfig.Arguments = append(svcConfig.Arguments, "--service-name", *fServiceName)
-
-			err := service.Control(s, *fService)
-			if err != nil {
-				log.Fatal("E! " + err.Error())
-			}
-			os.Exit(0)
-		} else {
-			winlogger, err := s.Logger(nil)
-			if err == nil {
-				//When in service mode, register eventlog target andd setup default logging to eventlog
-				logger.RegisterEventLogger(winlogger)
-				logger.SetupLogging(logger.LogConfig{LogTarget: logger.LogTargetEventlog})
-			}
-			err = s.Run()
-
-			if err != nil {
-				log.Println("E! " + err.Error())
-			}
-		}
-	} else {
-		stop = make(chan struct{})
-		reloadLoop(
-			stop,
+	run(
 		inputFilters,
 		outputFilters,
 		aggregatorFilters,
 		processorFilters,
 	)
 }
-}
-
-// Return true if Telegraf should create a Windows service.
-func windowsRunAsService() bool {
-	if *fService != "" {
-		return true
-	}
-
-	if *fRunAsConsole {
-		return false
-	}
-
-	return !service.Interactive()
-}

cmd/telegraf/telegraf_notwindows.go

@@ -0,0 +1,13 @@
+// +build !windows
+
+package main
+
+func run(inputFilters, outputFilters, aggregatorFilters, processorFilters []string) {
+	stop = make(chan struct{})
+	reloadLoop(
+		inputFilters,
+		outputFilters,
+		aggregatorFilters,
+		processorFilters,
+	)
+}

cmd/telegraf/telegraf_windows.go

@@ -0,0 +1,124 @@
+// +build windows
+
+package main
+
+import (
+	"log"
+	"os"
+	"runtime"
+
+	"github.com/influxdata/telegraf/logger"
+	"github.com/kardianos/service"
+)
+
+func run(inputFilters, outputFilters, aggregatorFilters, processorFilters []string) {
+	if runtime.GOOS == "windows" && windowsRunAsService() {
+		runAsWindowsService(
+			inputFilters,
+			outputFilters,
+			aggregatorFilters,
+			processorFilters,
+		)
+	} else {
+		stop = make(chan struct{})
+		reloadLoop(
+			inputFilters,
+			outputFilters,
+			aggregatorFilters,
+			processorFilters,
+		)
+	}
+}
+
+type program struct {
+	inputFilters      []string
+	outputFilters     []string
+	aggregatorFilters []string
+	processorFilters  []string
+}
+
+func (p *program) Start(s service.Service) error {
+	go p.run()
+	return nil
+}
+func (p *program) run() {
+	stop = make(chan struct{})
+	reloadLoop(
+		p.inputFilters,
+		p.outputFilters,
+		p.aggregatorFilters,
+		p.processorFilters,
+	)
+}
+func (p *program) Stop(s service.Service) error {
+	close(stop)
+	return nil
+}
+
+func runAsWindowsService(inputFilters, outputFilters, aggregatorFilters, processorFilters []string) {
+	programFiles := os.Getenv("ProgramFiles")
+	if programFiles == "" { // Should never happen
+		programFiles = "C:\\Program Files"
+	}
+	svcConfig := &service.Config{
+		Name:        *fServiceName,
+		DisplayName: *fServiceDisplayName,
+		Description: "Collects data using a series of plugins and publishes it to" +
+			"another series of plugins.",
+		Arguments: []string{"--config", programFiles + "\\Telegraf\\telegraf.conf"},
+	}
+
+	prg := &program{
+		inputFilters:      inputFilters,
+		outputFilters:     outputFilters,
+		aggregatorFilters: aggregatorFilters,
+		processorFilters:  processorFilters,
+	}
+	s, err := service.New(prg, svcConfig)
+	if err != nil {
+		log.Fatal("E! " + err.Error())
+	}
+	// Handle the --service flag here to prevent any issues with tooling that
+	// may not have an interactive session, e.g. installing from Ansible.
+	if *fService != "" {
+		if *fConfig != "" {
+			svcConfig.Arguments = []string{"--config", *fConfig}
+		}
+		if *fConfigDirectory != "" {
+			svcConfig.Arguments = append(svcConfig.Arguments, "--config-directory", *fConfigDirectory)
+		}
+		//set servicename to service cmd line, to have a custom name after relaunch as a service
+		svcConfig.Arguments = append(svcConfig.Arguments, "--service-name", *fServiceName)
+
+		err := service.Control(s, *fService)
+		if err != nil {
+			log.Fatal("E! " + err.Error())
+		}
+		os.Exit(0)
+	} else {
+		winlogger, err := s.Logger(nil)
+		if err == nil {
+			//When in service mode, register eventlog target andd setup default logging to eventlog
+			logger.RegisterEventLogger(winlogger)
+			logger.SetupLogging(logger.LogConfig{LogTarget: logger.LogTargetEventlog})
+		}
+		err = s.Run()
+
+		if err != nil {
+			log.Println("E! " + err.Error())
+		}
+	}
+}
+
+// Return true if Telegraf should create a Windows service.
+func windowsRunAsService() bool {
+	if *fService != "" {
+		return true
+	}
+
+	if *fRunAsConsole {
+		return false
+	}
+
+	return !service.Interactive()
+}

docs/OUTPUTS.md

@@ -94,6 +94,19 @@ You should also add the following to your `SampleConfig()`:
   data_format = "influx"
 ```
 
+## Flushing Metrics to Outputs
+
+Metrics are flushed to outputs when any of the following events happen:
+- `flush_interval + rand(flush_jitter)` has elapsed since start or the last flush interval
+- At least `metric_batch_size` count of metrics are waiting in the buffer
+- The telegraf process has received a SIGUSR1 signal
+
+Note that if the flush takes longer than the `agent.interval` to write the metrics
+to the output, you'll see a message saying the output `did not complete within its 
+flush interval`. This may mean your output is not keeping up with the flow of metrics, 
+and you may want to look into enabling compression, reducing the size of your metrics, 
+or investigate other reasons why the writes might be taking longer than expected.
+
 [file]: https://github.com/influxdata/telegraf/tree/master/plugins/inputs/file
 [output data formats]: https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_OUTPUT.md
 [SampleConfig]: https://github.com/influxdata/telegraf/wiki/SampleConfig

internal/usage.go

@@ -32,8 +32,9 @@ The commands & flags are:
                                  Valid values are 'agent', 'global_tags', 'outputs',
                                  'processors', 'aggregators' and 'inputs'
   --sample-config                print out full sample configuration
-  --test                         gather metrics, print them out, and exit;
-                                 processors, aggregators, and outputs are not run
+  --test                         enable test mode: gather metrics, print them out,
+                                 and exit. Note: Test mode only runs inputs, not
+                                 processors, aggregators, or outputs
   --test-wait                    wait up to this many seconds for service
                                  inputs to complete in test mode
   --usage <plugin>               print usage for a plugin, ie, 'telegraf --usage mysql'

internal/usage_windows.go

@@ -29,8 +29,9 @@ The commands & flags are:
   --section-filter               filter config sections to output, separator is :
                                  Valid values are 'agent', 'global_tags', 'outputs',
                                  'processors', 'aggregators' and 'inputs'
-  --test                         gather metrics, print them out, and exit;
-                                 processors, aggregators, and outputs are not run
+  --test                         enable test mode: gather metrics, print them out,
+                                 and exit. Note: Test mode only runs inputs, not
+                                 processors, aggregators, or outputs
   --test-wait                    wait up to this many seconds for service
                                  inputs to complete in test mode
   --usage <plugin>               print usage for a plugin, ie, 'telegraf --usage mysql'