remove interval configuration

plugins/inputs/sysstat/README.md

@@ -11,11 +11,6 @@ the created binary data file with the `sadf` utility.
 ```toml
 # Sysstat metrics collector
 [[inputs.sysstat]]
-  ## Collect interval in seconds. This value has to be equal
-  ## to the telegraf collect interval.
-  collect_interval = 30 # required
-  #
-  #
   ## Path to the sadc command.
   sadc_path = "/usr/lib/sa/sadc" # required
   #
@@ -127,7 +122,6 @@ And more if you define some `device_tags`.
 With the configuration below:
 ```toml
 [[inputs.sysstat]]
-  collect_interval = 30
   sadc_path = "/usr/lib/sa/sadc" # required
   activities = ["DISK", "SNMP", "INT"]
   group = true
@@ -196,7 +190,6 @@ $ telegraf -config telegraf.conf -input-filter sysstat -test
 If you change the group value to false like below:
 ```toml
 [[inputs.sysstat]]
-  collect_interval = 30
   sadc_path = "/usr/lib/sa/sadc" # required
   activities = ["DISK", "SNMP", "INT"]
   group = false

plugins/inputs/sysstat/sysstat.go

@@ -21,18 +21,14 @@ import (
 )
 
 var (
+	firstTimestamp time.Time
 	execCommand    = exec.Command // execCommand is used to mock commands in tests.
 	dfltActivities = []string{"DISK"}
 )
 
-const parseInterval = 1 // parseInterval is the interval (in seconds) where the parsing takes place.
+const parseInterval = 1 // parseInterval is the interval (in seconds) where the parsing of the binary file takes place.
 
 type Sysstat struct {
-	// Interval that defines how long data is collected by Sadc cmd.
-	//
-	// This value has to be the same as the thelegraf collection interval.
-	Interval int `toml:"collect_interval"`
-
 	// Sadc represents the path to the sadc collector utility.
 	Sadc string `toml:"sadc_path"`
 
@@ -66,18 +62,14 @@ type Sysstat struct {
 	// DeviceTags adds the possibility to add additional tags for devices.
 	DeviceTags map[string][]map[string]string `toml:"device_tags"`
 	tmpFile    string
+	interval   int
 }
 
 func (*Sysstat) Description() string {
 	return "Sysstat metrics collector"
 }
 
 var sampleConfig = `
-  ## Collect interval in seconds. This value has to be equal
-  ## to the telegraf collect interval.
-  collect_interval = 5 # required
-  #
-  #
   ## Path to the sadc command.
   sadc_path = "/usr/lib/sa/sadc" # required
   #
@@ -101,15 +93,14 @@ var sampleConfig = `
   # group = false
   #
   #
-  ## Options for the sasf command. The values on the left represent the sadf options and
+  ## Options for the sadf command. The values on the left represent the sadf options and
   ## the values on the right their description (wich are used for grouping and prefixing metrics).
   [inputs.sysstat.options]
 	-C = "cpu"
 	-B = "paging"
 	-b = "io"
 	-d = "disk"             # requires DISK activity
 	-H = "hugepages"
-	"-I ALL" = "interrupts" # requires INT activity
 	"-n ALL" = "network"
 	"-P ALL" = "per_cpu"
 	-q = "queue"
@@ -120,6 +111,7 @@ var sampleConfig = `
 	-v = "inode"
 	-W = "swap"
 	-w = "task"
+  #	"-I ALL" = "interrupts" # requires INT activity
   #
   #
   ## Device tags can be used to add additional tags for devices. For example the configuration below
@@ -133,7 +125,14 @@ func (*Sysstat) SampleConfig() string {
 }
 
 func (s *Sysstat) Gather(acc telegraf.Accumulator) error {
-	ts := time.Now().Add(time.Duration(s.Interval) * time.Second)
+	if s.interval == 0 {
+		if firstTimestamp.IsZero() {
+			firstTimestamp = time.Now()
+		} else {
+			s.interval = int(time.Since(firstTimestamp).Seconds())
+		}
+	}
+	ts := time.Now().Add(time.Duration(s.interval) * time.Second)
 	if err := s.collect(); err != nil {
 		return err
 	}
@@ -187,7 +186,12 @@ func (s *Sysstat) collect() error {
 		options = append(options, "-S", act)
 	}
 	s.tmpFile = path.Join("/tmp", fmt.Sprintf("sysstat-%d", time.Now().Unix()))
-	collectInterval := s.Interval - parseInterval // collectInterval has to be smaller than the telegraf data collection interval
+	collectInterval := s.interval - parseInterval // collectInterval has to be smaller than the telegraf data collection interval
+
+	if collectInterval < 0 { // If true, interval is not defined yet and Gather is run for the first time.
+		collectInterval = 1 // In that case we only collect for 1 second.
+	}
+
 	options = append(options, strconv.Itoa(collectInterval), "2", s.tmpFile)
 	cmd := execCommand(s.Sadc, options...)
 	out, err := cmd.CombinedOutput()

plugins/inputs/sysstat/sysstat_test.go

@@ -8,12 +8,13 @@ import (
 	"os/exec"
 	"path"
 	"testing"
+	"time"
 
 	"github.com/influxdata/telegraf/testutil"
 )
 
 var s = Sysstat{
-	Interval:   10,
+	interval:   10,
 	Sadc:       "/usr/lib/sa/sadc",
 	Group:      false,
 	Activities: []string{"DISK", "SNMP"},
@@ -303,3 +304,30 @@ dell-xps	5	2016-03-25 16:18:10 UTC	sdb	%util	0.30
 	// some code here to check arguments perhaps?
 	os.Exit(0)
 }
+
+// TestGatherInterval checks that interval is correctly set.
+func TestGatherInterval(t *testing.T) {
+	// overwriting exec commands with mock commands
+	execCommand = fakeExecCommand
+	defer func() { execCommand = exec.Command }()
+	var acc testutil.Accumulator
+
+	s.interval = 0
+	wantedInterval := 3
+
+	err := s.Gather(&acc)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	time.Sleep(time.Duration(wantedInterval) * time.Second)
+
+	err = s.Gather(&acc)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if s.interval != wantedInterval {
+		t.Errorf("wrong interval: got %d, want %d", s.interval, wantedInterval)
+	}
+}