agent: limit HTTP check output to 4k

command/agent/check.go

@@ -2,7 +2,7 @@ package agent
 
 import (
 	"fmt"
-	"io/ioutil"
+	"io"
 	"log"
 	"net"
 	"net/http"
@@ -423,13 +423,14 @@ func (c *CheckHTTP) check() {
 	}
 	defer resp.Body.Close()
 
-	// Format the response body
-	body, err := ioutil.ReadAll(resp.Body)
-	if err != nil {
+	// Read the response into a circular buffer to limit the size
+	output, _ := circbuf.NewBuffer(CheckBufSize)
+	if _, err := io.Copy(output, resp.Body); err != nil {
 		c.Logger.Printf("[WARN] agent: check '%v': Get error while reading body: %s", c.CheckID, err)
-		body = []byte{}
 	}
-	result := fmt.Sprintf("HTTP GET %s: %s Output: %s", c.HTTP, resp.Status, body)
+
+	// Format the response body
+	result := fmt.Sprintf("HTTP GET %s: %s Output: %s", c.HTTP, resp.Status, output.String())
 
 	if resp.StatusCode >= 200 && resp.StatusCode <= 299 {
 		// PASSING (2xx)

command/agent/check_test.go

@@ -1,6 +1,7 @@
 package agent
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"log"
@@ -186,7 +187,10 @@ func TestCheckTTL(t *testing.T) {
 func mockHTTPServer(responseCode int) *httptest.Server {
 	mux := http.NewServeMux()
 	mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		// Body larger than 4k limit
+		body := bytes.Repeat([]byte{'a'}, 2*CheckBufSize)
 		w.WriteHeader(responseCode)
+		w.Write(body)
 		return
 	})
 
@@ -219,6 +223,11 @@ func expectHTTPStatus(t *testing.T, url string, status string) {
 	if mock.state["foo"] != status {
 		t.Fatalf("should be %v %v", status, mock.state)
 	}
+
+	// Allow slightly more data than CheckBufSize, for the header
+	if n := len(mock.output["foo"]); n > (CheckBufSize + 256) {
+		t.Fatalf("output too long: %d (%d-byte limit)", n, CheckBufSize)
+	}
 }
 
 func TestCheckHTTPCritical(t *testing.T) {