Exec probes should not be unbounded

In 1f270ef4e2, we added 10KB as the read
limit for http probes. we should do the same for exec probes as well.

Change-Id: If154c5c4e669829ab94839c56260a894a6714f0f

pkg/probe/exec/BUILD

@@ -11,6 +11,7 @@ go_library(
     srcs = ["exec.go"],
     importpath = "k8s.io/kubernetes/pkg/probe/exec",
     deps = [
+        "//pkg/kubelet/util/ioutils:go_default_library",
         "//pkg/probe:go_default_library",
         "//vendor/k8s.io/klog:go_default_library",
         "//vendor/k8s.io/utils/exec:go_default_library",

pkg/probe/exec/exec.go

@@ -17,10 +17,17 @@ limitations under the License.
 package exec
 
 import (
+	"bytes"
+
+	"k8s.io/kubernetes/pkg/kubelet/util/ioutils"
 	"k8s.io/kubernetes/pkg/probe"
-	"k8s.io/utils/exec"
 
 	"k8s.io/klog"
+	"k8s.io/utils/exec"
+)
+
+const (
+	maxReadLength = 10 * 1 << 10 // 10KB
 )
 
 // New creates a Prober.
@@ -39,7 +46,17 @@ type execProber struct{}
 // from executing a command. Returns the Result status, command output, and
 // errors if any.
 func (pr execProber) Probe(e exec.Cmd) (probe.Result, string, error) {
-	data, err := e.CombinedOutput()
+	var dataBuffer bytes.Buffer
+	writer := ioutils.LimitWriter(&dataBuffer, maxReadLength)
+
+	e.SetStderr(writer)
+	e.SetStdout(writer)
+	err := e.Start()
+	if err == nil {
+		err = e.Wait()
+	}
+	data := dataBuffer.Bytes()
+
 	klog.V(4).Infof("Exec probe response: %q", string(data))
 	if err != nil {
 		exit, ok := err.(exec.ExitError)

pkg/probe/exec/exec_test.go

@@ -19,6 +19,7 @@ package exec
 import (
 	"fmt"
 	"io"
+	"strings"
 	"testing"
 
 	"k8s.io/kubernetes/pkg/probe"
@@ -28,6 +29,7 @@ type FakeCmd struct {
 	out    []byte
 	stdout []byte
 	err    error
+	writer io.Writer
 }
 
 func (f *FakeCmd) Run() error {
@@ -46,15 +48,25 @@ func (f *FakeCmd) SetDir(dir string) {}
 
 func (f *FakeCmd) SetStdin(in io.Reader) {}
 
-func (f *FakeCmd) SetStdout(out io.Writer) {}
+func (f *FakeCmd) SetStdout(out io.Writer) {
+	f.writer = out
+}
 
-func (f *FakeCmd) SetStderr(out io.Writer) {}
+func (f *FakeCmd) SetStderr(out io.Writer) {
+	f.writer = out
+}
 
 func (f *FakeCmd) SetEnv(env []string) {}
 
 func (f *FakeCmd) Stop() {}
 
-func (f *FakeCmd) Start() error { return nil }
+func (f *FakeCmd) Start() error {
+	if f.writer != nil {
+		f.writer.Write(f.out)
+		return f.err
+	}
+	return f.err
+}
 
 func (f *FakeCmd) Wait() error { return nil }
 
@@ -90,20 +102,26 @@ func (f *fakeExitError) ExitStatus() int {
 func TestExec(t *testing.T) {
 	prober := New()
 
+	tenKilobyte := strings.Repeat("logs-123", 128*10)      // 8*128*10=10240 = 10KB of text.
+	elevenKilobyte := strings.Repeat("logs-123", 8*128*11) // 8*128*11=11264 = 11KB of text.
+
 	tests := []struct {
 		expectedStatus probe.Result
 		expectError    bool
+		input          string
 		output         string
 		err            error
 	}{
 		// Ok
-		{probe.Success, false, "OK", nil},
+		{probe.Success, false, "OK", "OK", nil},
 		// Ok
-		{probe.Success, false, "OK", &fakeExitError{true, 0}},
+		{probe.Success, false, "OK", "OK", &fakeExitError{true, 0}},
+		// Ok - truncated output
+		{probe.Success, false, elevenKilobyte, tenKilobyte, nil},
 		// Run returns error
-		{probe.Unknown, true, "", fmt.Errorf("test error")},
+		{probe.Unknown, true, "", "", fmt.Errorf("test error")},
 		// Unhealthy
-		{probe.Failure, false, "Fail", &fakeExitError{true, 1}},
+		{probe.Failure, false, "Fail", "", &fakeExitError{true, 1}},
 	}
 	for i, test := range tests {
 		fake := FakeCmd{