http listener refactor

in this commit:

- chunks out the http request body to avoid making very large
  allocations.
- establishes a limit for the maximum http request body size that the
  listener will accept.
- utilizes a pool of byte buffers to reduce GC pressure.

plugins/inputs/http_listener/bufferpool.go

@@ -0,0 +1,29 @@
+package http_listener
+
+type pool struct {
+	n       int
+	buffers chan []byte
+}
+
+func NewPool() *pool {
+	return &pool{
+		buffers: make(chan []byte, 50),
+	}
+}
+
+func (p *pool) get() []byte {
+	select {
+	case b := <-p.buffers:
+		return b
+	default:
+		return make([]byte, MAX_ALLOCATION_SIZE)
+	}
+}
+
+func (p *pool) put(b []byte) {
+	select {
+	case p.buffers <- b:
+	default:
+		// drop it
+	}
+}

plugins/inputs/http_listener/http_listener.go

@@ -1,9 +1,9 @@
 package http_listener
 
 import (
-	"bufio"
 	"bytes"
-	"fmt"
+	"compress/gzip"
+	"io"
 	"log"
 	"net"
 	"net/http"
@@ -17,18 +17,31 @@ import (
 	"github.com/influxdata/telegraf/plugins/parsers"
 )
 
+const (
+	// DEFAULT_REQUEST_BODY_MAX is the default maximum request body size, in bytes.
+	// if the request body is over this size, we will return an HTTP 413 error.
+	// 512 MB
+	DEFAULT_REQUEST_BODY_MAX = 512 * 1000 * 1000
+
+	// MAX_ALLOCATION_SIZE is the maximum size, in bytes, of a single allocation
+	// of bytes that will be made handling a single HTTP request.
+	// 1 MB
+	MAX_ALLOCATION_SIZE = 1 * 1000 * 1000
+)
+
 type HttpListener struct {
 	ServiceAddress string
 	ReadTimeout    internal.Duration
 	WriteTimeout   internal.Duration
+	MaxBodySize    int64
 
 	sync.Mutex
-	wg sync.WaitGroup
 
 	listener *stoppableListener.StoppableListener
 
 	parser parsers.Parser
 	acc    telegraf.Accumulator
+	pool   *pool
 }
 
 const sampleConfig = `
@@ -61,7 +74,12 @@ func (t *HttpListener) Start(acc telegraf.Accumulator) error {
 	t.Lock()
 	defer t.Unlock()
 
+	if t.MaxBodySize == 0 {
+		t.MaxBodySize = DEFAULT_REQUEST_BODY_MAX
+	}
+
 	t.acc = acc
+	t.pool = NewPool()
 
 	var rawListener, err = net.Listen("tcp", t.ServiceAddress)
 	if err != nil {
@@ -87,8 +105,6 @@ func (t *HttpListener) Stop() {
 	t.listener.Stop()
 	t.listener.Close()
 
-	t.wg.Wait()
-
 	log.Println("I! Stopped HTTP listener service on ", t.ServiceAddress)
 }
 
@@ -111,37 +127,9 @@ func (t *HttpListener) httpListen() error {
 }
 
 func (t *HttpListener) ServeHTTP(res http.ResponseWriter, req *http.Request) {
-	t.wg.Add(1)
-	defer t.wg.Done()
-
 	switch req.URL.Path {
 	case "/write":
-		var http400msg bytes.Buffer
-		var partial string
-		scanner := bufio.NewScanner(req.Body)
-		scanner.Buffer([]byte(""), 128*1024)
-		for scanner.Scan() {
-			metrics, err := t.parser.Parse(scanner.Bytes())
-			if err == nil {
-				for _, m := range metrics {
-					t.acc.AddFields(m.Name(), m.Fields(), m.Tags(), m.Time())
-				}
-				partial = "partial write: "
-			} else {
-				http400msg.WriteString(err.Error() + " ")
-			}
-		}
-
-		if err := scanner.Err(); err != nil {
-			http.Error(res, "Internal server error: "+err.Error(), http.StatusInternalServerError)
-		} else if http400msg.Len() > 0 {
-			res.Header().Set("Content-Type", "application/json")
-			res.Header().Set("X-Influxdb-Version", "1.0")
-			res.WriteHeader(http.StatusBadRequest)
-			res.Write([]byte(fmt.Sprintf(`{"error":"%s%s"}`, partial, http400msg.String())))
-		} else {
-			res.WriteHeader(http.StatusNoContent)
-		}
+		t.serveWrite(res, req)
 	case "/query":
 		// Deliver a dummy response to the query endpoint, as some InfluxDB
 		// clients test endpoint availability with a query
@@ -158,6 +146,98 @@ func (t *HttpListener) ServeHTTP(res http.ResponseWriter, req *http.Request) {
 	}
 }
 
+func (t *HttpListener) serveWrite(res http.ResponseWriter, req *http.Request) {
+	// Check that the content length is not too large for us to handle.
+	if req.ContentLength > t.MaxBodySize {
+		toolarge(res)
+		return
+	}
+
+	// Handle gzip request bodies
+	var body io.ReadCloser
+	if req.Header.Get("Content-Encoding") == "gzip" {
+		r, err := gzip.NewReader(req.Body)
+		if err != nil {
+			log.Println("E! " + err.Error())
+			badrequest(res)
+			return
+		}
+		body = http.MaxBytesReader(res, r, t.MaxBodySize)
+	} else {
+		body = http.MaxBytesReader(res, req.Body, t.MaxBodySize)
+	}
+
+	var return400 bool
+	var buf []byte
+	var nextbuf []byte
+	bufi := 0
+	for {
+		if len(nextbuf) == 0 {
+			buf = t.pool.get()
+		} else {
+			buf = nextbuf
+		}
+		n, err := io.ReadFull(body, buf[bufi:])
+
+		if err != nil && err != io.ErrUnexpectedEOF {
+			// problem reading the request body
+			badrequest(res)
+			t.pool.put(buf)
+			return
+		}
+
+		if err == io.ErrUnexpectedEOF || n == 0 {
+			// finished reading the request body
+			if err := t.parse(buf[:n+bufi]); err != nil {
+				log.Println("E! " + err.Error())
+				return400 = true
+			}
+			t.pool.put(buf)
+			if return400 {
+				badrequest(res)
+			} else {
+				res.WriteHeader(http.StatusNoContent)
+			}
+			return
+		}
+
+		i := bytes.LastIndexByte(buf, '\n')
+		// TODO handle a line longer than the max buffer size
+		if err := t.parse(buf[:i]); err != nil {
+			log.Println("E! " + err.Error())
+			return400 = true
+		}
+		nextbuf = t.pool.get()
+		copy(nextbuf[:len(buf)-i], buf[i:])
+		bufi = len(buf) - i
+		t.pool.put(buf)
+	}
+}
+
+func (t *HttpListener) parse(b []byte) error {
+	metrics, err := t.parser.Parse(b)
+
+	for _, m := range metrics {
+		t.acc.AddFields(m.Name(), m.Fields(), m.Tags(), m.Time())
+	}
+
+	return err
+}
+
+func toolarge(res http.ResponseWriter) {
+	res.Header().Set("Content-Type", "application/json")
+	res.Header().Set("X-Influxdb-Version", "1.0")
+	res.WriteHeader(http.StatusRequestEntityTooLarge)
+	res.Write([]byte(`{"error":"http: request body too large"}`))
+}
+
+func badrequest(res http.ResponseWriter) {
+	res.Header().Set("Content-Type", "application/json")
+	res.Header().Set("X-Influxdb-Version", "1.0")
+	res.WriteHeader(http.StatusBadRequest)
+	res.Write([]byte(`{"error":"http: bad request"}`))
+}
+
 func init() {
 	inputs.Add("http_listener", func() telegraf.Input {
 		return &HttpListener{}