context_test.go

// -*- Mode: Go; indent-tabs-mode: t -*-

/*
 * Copyright (C) 2018 Canonical Ltd
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 3 as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

package osutil_test

import (
	"context"
	"io"
	"os/exec"
	"strings"
	"testing"
	"time"

	"gopkg.in/check.v1"

	"github.com/snapcore/snapd/osutil"
)

type ctxSuite struct{}

type dumbReader struct{}

func (dumbReader) Read([]byte) (int, error) {
	return 1, nil
}

var _ = check.Suite(&ctxSuite{})

func (ctxSuite) TestWriter(c *check.C) {
	ctx, cancel := context.WithTimeout(context.Background(), time.Second/100)
	defer cancel()
	n, err := io.Copy(osutil.ContextWriter(ctx), dumbReader{})
	c.Assert(err, check.Equals, context.DeadlineExceeded)
	// but we copied things until the deadline hit
	c.Check(n, check.Not(check.Equals), int64(0))
}

func (ctxSuite) TestWriterDone(c *check.C) {
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	n, err := io.Copy(osutil.ContextWriter(ctx), dumbReader{})
	c.Assert(err, check.Equals, context.Canceled)
	// and nothing was copied
	c.Check(n, check.Equals, int64(0))
}

func (ctxSuite) TestWriterSuccess(c *check.C) {
	ctx, cancel := context.WithTimeout(context.Background(), time.Second/100)
	defer cancel()
	// check we can copy if we're quick
	n, err := io.Copy(osutil.ContextWriter(ctx), strings.NewReader("hello"))
	c.Check(err, check.IsNil)
	c.Check(n, check.Equals, int64(len("hello")))
}

func (ctxSuite) TestRun(c *check.C) {
	ctx, cancel := context.WithTimeout(context.Background(), time.Second/100)
	defer cancel()
	cmd := exec.Command("/bin/sleep", "1")
	err := osutil.RunWithContext(ctx, cmd)
	c.Check(err, check.Equals, context.DeadlineExceeded)
}

func (ctxSuite) TestRunRace(c *check.C) {
	if testing.Short() {
		c.Skip("skippinng non-short test")
	}

	// first, time how long /bin/false takes
	t0 := time.Now()
	cmderr := exec.Command("/bin/false").Run()
	dt := time.Since(t0)

	// note in particular the error is not "killed"
	c.Assert(cmderr, check.ErrorMatches, "exit status 1")
	failedstr := cmderr.Error()
	killedstr := context.DeadlineExceeded.Error()

	// now run it in a loop with a deadline of exactly that
	nkilled := 0
	nfailed := 0
	for nfailed == 0 || nkilled == 0 {
		cmd := exec.Command("/bin/false")
		ctx, cancel := context.WithTimeout(context.Background(), dt)
		err := osutil.RunWithContext(ctx, cmd)
		cancel()
		switch err.Error() {
		case killedstr:
			nkilled++
		case failedstr:
			nfailed++
		default:
			// if the error is anything other than due to the context
			// being done, or the command failing, there's a bug.
			c.Fatalf("expected %q or %q, got %q", failedstr, killedstr, err)
		}
	}
}

func (ctxSuite) TestRunDone(c *check.C) {
	ctx, cancel := context.WithCancel(context.Background())
	cancel()
	cmd := exec.Command("/bin/sleep", "1")
	err := osutil.RunWithContext(ctx, cmd)
	c.Check(err, check.Equals, context.Canceled)
}

func (ctxSuite) TestRunSuccess(c *check.C) {
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()
	cmd := exec.Command("/bin/sleep", "0.01")
	err := osutil.RunWithContext(ctx, cmd)
	c.Check(err, check.IsNil)
}

func (ctxSuite) TestRunSuccessfulFailure(c *check.C) {
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()
	cmd := exec.Command("not/something/you/can/run")
	err := osutil.RunWithContext(ctx, cmd)
	c.Check(err, check.ErrorMatches, `fork/exec \S+: no such file or directory`)
}