Implement a per-output fixed size metric buffer

Also moved some objects out of config.go and put them in their own
package, internal/models

fixes #568
closes #285

plugins/inputs/docker/docker.go

@@ -110,15 +110,12 @@ func (d *Docker) gatherContainer(
 		Timeout: time.Duration(time.Second * 5),
 	}
 
-	var err error
 	go func() {
-		err = d.client.Stats(statOpts)
+		d.client.Stats(statOpts)
 	}()
 
 	stat := <-statChan
-	if err != nil {
-		return err
-	}
+	close(done)
 
 	// Add labels to tags
 	for k, v := range container.Labels {

plugins/inputs/influxdb/influxdb.go

@@ -130,7 +130,7 @@ func (i *InfluxDB) gatherURL(
 		p.Tags["url"] = url
 
 		acc.AddFields(
-			p.Name,
+			"influxdb_"+p.Name,
 			p.Values,
 			p.Tags,
 		)

plugins/inputs/influxdb/influxdb_test.go

@@ -84,7 +84,7 @@ func TestBasic(t *testing.T) {
 		"id":  "ex1",
 		"url": fakeServer.URL + "/endpoint",
 	}
-	acc.AssertContainsTaggedFields(t, "foo", fields, tags)
+	acc.AssertContainsTaggedFields(t, "influxdb_foo", fields, tags)
 
 	fields = map[string]interface{}{
 		"x": "x",
@@ -93,5 +93,5 @@ func TestBasic(t *testing.T) {
 		"id":  "ex2",
 		"url": fakeServer.URL + "/endpoint",
 	}
-	acc.AssertContainsTaggedFields(t, "bar", fields, tags)
+	acc.AssertContainsTaggedFields(t, "influxdb_bar", fields, tags)
 }

plugins/inputs/procstat/procstat.go

@@ -129,9 +129,13 @@ func pidsFromFile(file string) ([]int32, error) {
 func pidsFromExe(exe string) ([]int32, error) {
 	var out []int32
 	var outerr error
-	pgrep, err := exec.Command("pgrep", exe).Output()
+	bin, err := exec.LookPath("pgrep")
 	if err != nil {
-		return out, fmt.Errorf("Failed to execute pgrep. Error: '%s'", err)
+		return out, fmt.Errorf("Couldn't find pgrep binary: %s", err)
+	}
+	pgrep, err := exec.Command(bin, exe).Output()
+	if err != nil {
+		return out, fmt.Errorf("Failed to execute %s. Error: '%s'", bin, err)
 	} else {
 		pids := strings.Fields(string(pgrep))
 		for _, pid := range pids {
@@ -149,9 +153,13 @@ func pidsFromExe(exe string) ([]int32, error) {
 func pidsFromPattern(pattern string) ([]int32, error) {
 	var out []int32
 	var outerr error
-	pgrep, err := exec.Command("pgrep", "-f", pattern).Output()
+	bin, err := exec.LookPath("pgrep")
 	if err != nil {
-		return out, fmt.Errorf("Failed to execute pgrep. Error: '%s'", err)
+		return out, fmt.Errorf("Couldn't find pgrep binary: %s", err)
+	}
+	pgrep, err := exec.Command(bin, "-f", pattern).Output()
+	if err != nil {
+		return out, fmt.Errorf("Failed to execute %s. Error: '%s'", bin, err)
 	} else {
 		pids := strings.Fields(string(pgrep))
 		for _, pid := range pids {