Moved system package inputs out to top level (#4406)

plugins/inputs/mem/README.md

@@ -0,0 +1,35 @@
+# Mem Input Plugin
+
+The mem plugin collects system memory metrics.
+
+For a more complete explanation of the difference between *used* and
+*actual_used* RAM, see [Linux ate my ram](http://www.linuxatemyram.com/).
+
+### Configuration:
+```toml
+# Read metrics about memory usage
+[[inputs.mem]]
+  # no configuration
+```
+
+### Metrics:
+
+- mem
+  - fields:
+  	- active (int)
+  	- available (int)
+  	- buffered (int)
+  	- cached (int)
+  	- free (int)
+  	- inactive (int)
+  	- slab (int)
+  	- total (int)
+  	- used (int)
+  	- available_percent (float)
+  	- used_percent (float)
+  	- wired (int)
+
+### Example Output:
+```
+mem cached=7809495040i,inactive=6348988416i,total=20855394304i,available=11378946048i,buffered=927199232i,active=11292905472i,slab=1351340032i,used_percent=45.43883523785713,available_percent=54.56116476214287,used=9476448256i,free=1715331072i 1511894782000000000
+```

plugins/inputs/mem/memory.go

@@ -0,0 +1,51 @@
+package mem
+
+import (
+	"fmt"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/inputs"
+	"github.com/influxdata/telegraf/plugins/inputs/system"
+)
+
+type MemStats struct {
+	ps system.PS
+}
+
+func (_ *MemStats) Description() string {
+	return "Read metrics about memory usage"
+}
+
+func (_ *MemStats) SampleConfig() string { return "" }
+
+func (s *MemStats) Gather(acc telegraf.Accumulator) error {
+	vm, err := s.ps.VMStat()
+	if err != nil {
+		return fmt.Errorf("error getting virtual memory info: %s", err)
+	}
+
+	fields := map[string]interface{}{
+		"total":             vm.Total,
+		"available":         vm.Available,
+		"used":              vm.Used,
+		"free":              vm.Free,
+		"cached":            vm.Cached,
+		"buffered":          vm.Buffers,
+		"active":            vm.Active,
+		"inactive":          vm.Inactive,
+		"wired":             vm.Wired,
+		"slab":              vm.Slab,
+		"used_percent":      100 * float64(vm.Used) / float64(vm.Total),
+		"available_percent": 100 * float64(vm.Available) / float64(vm.Total),
+	}
+	acc.AddGauge("mem", fields, nil)
+
+	return nil
+}
+
+func init() {
+	ps := system.NewSystemPS()
+	inputs.Add("mem", func() telegraf.Input {
+		return &MemStats{ps: ps}
+	})
+}

plugins/inputs/mem/memory_test.go

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+package mem
+
+import (
+	"testing"
+
+	"github.com/influxdata/telegraf/plugins/inputs/system"
+	"github.com/influxdata/telegraf/testutil"
+	"github.com/shirou/gopsutil/mem"
+	"github.com/stretchr/testify/require"
+)
+
+func TestMemStats(t *testing.T) {
+	var mps system.MockPS
+	var err error
+	defer mps.AssertExpectations(t)
+	var acc testutil.Accumulator
+
+	vms := &mem.VirtualMemoryStat{
+		Total:     12400,
+		Available: 7600,
+		Used:      5000,
+		Free:      1235,
+		Active:    8134,
+		Inactive:  1124,
+		Slab:      1234,
+		Wired:     134,
+		// Buffers:     771,
+		// Cached:      4312,
+		// Shared:      2142,
+	}
+
+	mps.On("VMStat").Return(vms, nil)
+
+	err = (&MemStats{&mps}).Gather(&acc)
+	require.NoError(t, err)
+
+	memfields := map[string]interface{}{
+		"total":             uint64(12400),
+		"available":         uint64(7600),
+		"used":              uint64(5000),
+		"available_percent": float64(7600) / float64(12400) * 100,
+		"used_percent":      float64(5000) / float64(12400) * 100,
+		"free":              uint64(1235),
+		"cached":            uint64(0),
+		"buffered":          uint64(0),
+		"active":            uint64(8134),
+		"inactive":          uint64(1124),
+		"wired":             uint64(134),
+		"slab":              uint64(1234),
+	}
+	acc.AssertContainsTaggedFields(t, "mem", memfields, make(map[string]string))
+
+	acc.Metrics = nil
+}