Return error when child exits early

PiperOrigin-RevId: 195365050
Change-Id: I8754dc7a3fc2975d422cae453762a455478a8e6a

3 files changed, 136 insertions, 1 deletions

diff --git a/runsc/specutils/BUILD b/runsc/specutils/BUILD
index ae89260d2..1b6d265bc 100644
--- a/runsc/specutils/BUILD
+++ b/runsc/specutils/BUILD
@@ -1,6 +1,6 @@
 package(licenses = ["notice"])  # Apache 2.0
 
-load("@io_bazel_rules_go//go:def.bzl", "go_library")
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
 
 go_library(
     name = "specutils",
@@ -16,3 +16,10 @@ go_library(
         "@com_github_opencontainers_runtime-spec//specs-go:go_default_library",
     ],
 )
+
+go_test(
+    name = "specutils_test",
+    size = "small",
+    srcs = ["specutils_test.go"],
+    embed = [":specutils"],
+)
diff --git a/runsc/specutils/specutils.go b/runsc/specutils/specutils.go
index bed0f75eb..04ecb6ae3 100644
--- a/runsc/specutils/specutils.go
+++ b/runsc/specutils/specutils.go
@@ -23,6 +23,8 @@ import (
 	"os"
 	"path/filepath"
 	"strings"
+	"syscall"
+	"time"
 
 	specs "github.com/opencontainers/runtime-spec/specs-go"
 	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
@@ -181,3 +183,33 @@ func BinPath() (string, error) {
 	}
 	return binPath, nil
 }
+
+// WaitForReady waits for a process to become ready. The process is ready when
+// the 'ready' function returns true. It continues to wait if 'ready' returns
+// false. It returns error on timeout, if the process stops or if 'ready' fails.
+func WaitForReady(pid int, timeout time.Duration, ready func() (bool, error)) error {
+	backoff := 1 * time.Millisecond
+	for start := time.Now(); time.Now().Sub(start) < timeout; {
+		if ok, err := ready(); err != nil {
+			return err
+		} else if ok {
+			return nil
+		}
+
+		// Check if the process is still running.
+		var ws syscall.WaitStatus
+		var ru syscall.Rusage
+		child, err := syscall.Wait4(pid, &ws, syscall.WNOHANG, &ru)
+		if err != nil || child == pid {
+			return fmt.Errorf("process (%d) is not running, err: %v", pid, err)
+		}
+
+		// Process continues to run, backoff and retry.
+		time.Sleep(backoff)
+		backoff *= 2
+		if backoff > 1*time.Second {
+			backoff = 1 * time.Second
+		}
+	}
+	return fmt.Errorf("timed out waiting for process (%d)", pid)
+}
diff --git a/runsc/specutils/specutils_test.go b/runsc/specutils/specutils_test.go
new file mode 100644
index 000000000..ef293e608
--- /dev/null
+++ b/runsc/specutils/specutils_test.go
@@ -0,0 +1,96 @@
+// Copyright 2018 Google Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package specutils
+
+import (
+	"fmt"
+	"os/exec"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestWaitForReadyHappy(t *testing.T) {
+	cmd := exec.Command("/bin/sleep", "1000")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("cmd.Start() failed, err: %v", err)
+	}
+	defer cmd.Wait()
+
+	var count int
+	err := WaitForReady(cmd.Process.Pid, 5*time.Second, func() (bool, error) {
+		if count < 3 {
+			count++
+			return false, nil
+		}
+		return true, nil
+	})
+	if err != nil {
+		t.Errorf("ProcessWaitReady got: %v, expected: nil", err)
+	}
+	cmd.Process.Kill()
+}
+
+func TestWaitForReadyFail(t *testing.T) {
+	cmd := exec.Command("/bin/sleep", "1000")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("cmd.Start() failed, err: %v", err)
+	}
+	defer cmd.Wait()
+
+	var count int
+	err := WaitForReady(cmd.Process.Pid, 5*time.Second, func() (bool, error) {
+		if count < 3 {
+			count++
+			return false, nil
+		}
+		return false, fmt.Errorf("Fake error")
+	})
+	if err == nil {
+		t.Errorf("ProcessWaitReady got: nil, expected: error")
+	}
+	cmd.Process.Kill()
+}
+
+func TestWaitForReadyNotRunning(t *testing.T) {
+	cmd := exec.Command("/bin/true")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("cmd.Start() failed, err: %v", err)
+	}
+	defer cmd.Wait()
+
+	err := WaitForReady(cmd.Process.Pid, 5*time.Second, func() (bool, error) {
+		return false, nil
+	})
+	if !strings.Contains(err.Error(), "not running") {
+		t.Errorf("ProcessWaitReady got: %v, expected: not running", err)
+	}
+}
+
+func TestWaitForReadyTimeout(t *testing.T) {
+	cmd := exec.Command("/bin/sleep", "1000")
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("cmd.Start() failed, err: %v", err)
+	}
+	defer cmd.Wait()
+
+	err := WaitForReady(cmd.Process.Pid, 50*time.Millisecond, func() (bool, error) {
+		return false, nil
+	})
+	if !strings.Contains(err.Error(), "timed out") {
+		t.Errorf("ProcessWaitReady got: %v, expected: timed out", err)
+	}
+	cmd.Process.Kill()
+}