test.go

// /bin/true; exec /usr/bin/env go run "$0" "$@"

/*
 * Copyright 2019 The Vitess Authors.

 * 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.
 */

/*
test.go is a "Go script" for running Vitess tests. It runs each test in its own
Docker container for hermeticity and (potentially) parallelism. If a test fails,
this script will save the output in _test/ and continue with other tests.

Before using it, you should have Docker 1.5+ installed, and have your user in
the group that lets you run the docker command without sudo. The first time you
run against a given flavor, it may take some time for the corresponding
bootstrap image (vitess/bootstrap:<flavor>) to be downloaded.

It is meant to be run from the Vitess root, like so:

	$ go run test.go [args]

For a list of options, run:

	$ go run test.go --help
*/
package main

// This Go script shouldn't rely on any packages that aren't in the standard
// library, since that would require the user to bootstrap before running it.
import (
	"bytes"
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"log"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"os/signal"
	"path"
	"path/filepath"
	"sort"
	"strconv"
	"strings"
	"sync"
	"syscall"
	"time"
)

var usage = `Usage of test.go:

go run test.go [options] [test_name ...] [-- extra-py-test-args]

If one or more test names are provided, run only those tests.
Otherwise, run all tests in test/config.json.

To pass extra args to Python tests (test/*.py), terminate the
list of test names with -- and then add them at the end.

For example:
  go run test.go test1 test2 -- --topo-flavor=etcd2
`

// Flags
var (
	flavor           = flag.String("flavor", "mysql57", "comma-separated bootstrap flavor(s) to run against (when using Docker mode). Available flavors: all,"+flavors)
	bootstrapVersion = flag.String("bootstrap-version", "11.2", "the version identifier to use for the docker images")
	runCount         = flag.Int("runs", 1, "run each test this many times")
	retryMax         = flag.Int("retry", 3, "max number of retries, to detect flaky tests")
	logPass          = flag.Bool("log-pass", false, "log test output even if it passes")
	timeout          = flag.Duration("timeout", 30*time.Minute, "timeout for each test")
	pull             = flag.Bool("pull", true, "re-pull the bootstrap image, in case it's been updated")
	docker           = flag.Bool("docker", true, "run tests with Docker")
	useDockerCache   = flag.Bool("use_docker_cache", false, "if true, create a temporary Docker image to cache the source code and the binaries generated by 'make build'. Used for execution on Travis CI.")
	shard            = flag.String("shard", "", "if non-empty, run the tests whose Shard field matches value")
	tag              = flag.String("tag", "", "if provided, only run tests with the given tag. Can't be combined with -shard or explicit test list")
	exclude          = flag.String("exclude", "", "if provided, exclude tests containing any of the given tags (comma delimited)")
	keepData         = flag.Bool("keep-data", false, "don't delete the per-test VTDATAROOT subfolders")
	printLog         = flag.Bool("print-log", false, "print the log of each failed test (or all tests if -log-pass) to the console")
	follow           = flag.Bool("follow", false, "print test output as it runs, instead of waiting to see if it passes or fails")
	parallel         = flag.Int("parallel", 1, "number of tests to run in parallel")
	skipBuild        = flag.Bool("skip-build", false, "skip running 'make build'. Assumes pre-existing binaries exist")
	partialKeyspace  = flag.Bool("partial-keyspace", false, "add a second keyspace for sharded tests and mark first shard as moved to this keyspace in the shard routing rules")
	// `go run test.go --dry-run --skip-build` to quickly test this file and see what tests will run
	dryRun      = flag.Bool("dry-run", false, "For each test to be run, it will output the test attributes, but NOT run the tests. Useful while debugging changes to test.go (this file)")
	remoteStats = flag.String("remote-stats", "", "url to send remote stats")
)

var (
	vtDataRoot = os.Getenv("VTDATAROOT")

	extraArgs []string
)

const (
	statsFileName  = "test/stats.json"
	configFileName = "test/config.json"

	// List of flavors for which a bootstrap Docker image is available.
	flavors = "mysql56,mysql57,mysql80,mariadb,mariadb103,percona,percona57,percona80"
)

// Config is the overall object serialized in test/config.json.
type Config struct {
	Tests map[string]*Test
}

// Test is an entry from the test/config.json file.
type Test struct {
	File          string
	Args, Command []string

	// Manual means it won't be run unless explicitly specified.
	Manual bool

	// Shard is used to split tests among workers.
	Shard string

	// RetryMax is the maximum number of times a test will be retried.
	// If 0, flag *retryMax is used.
	RetryMax int

	// Tags is a list of tags that can be used to filter tests.
	Tags []string

	name             string
	flavor           string
	bootstrapVersion string
	runIndex         int

	pass, fail int
}

func (t *Test) hasTag(want string) bool {
	for _, got := range t.Tags {
		if got == want {
			return true
		}
	}
	return false
}

func (t *Test) hasAnyTag(want []string) bool {
	for _, tag := range want {
		if t.hasTag(tag) {
			return true
		}
	}
	return false
}

// run executes a single try.
// dir is the location of the vitess repo to use.
// dataDir is the VTDATAROOT to use for this run.
// returns the combined stdout+stderr and error.
func (t *Test) run(dir, dataDir string) ([]byte, error) {
	if *dryRun {
		fmt.Printf("Will run in dir %s(%s): %+v\n", dir, dataDir, t)
		t.pass++
		return nil, nil
	}
	testCmd := t.Command
	if len(testCmd) == 0 {
		if strings.Contains(fmt.Sprintf("%v", t.File), ".go") {
			testCmd = []string{"tools/e2e_go_test.sh"}
			testCmd = append(testCmd, t.Args...)
			if *keepData {
				testCmd = append(testCmd, "-keep-data")
			}
		} else {
			testCmd = []string{"test/" + t.File, "-v", "--skip-build", "--keep-logs"}
			testCmd = append(testCmd, t.Args...)
		}
		if *partialKeyspace {
			testCmd = append(testCmd, "--partial-keyspace")
		}
		testCmd = append(testCmd, extraArgs...)
		if *docker {
			// Teardown is unnecessary since Docker kills everything.
			// Go cluster doesn't recognize 'skip-teardown' flag so commenting it out for now.
			// testCmd = append(testCmd, "--skip-teardown")
		}
	}

	var cmd *exec.Cmd
	if *docker {
		var args []string
		testArgs := strings.Join(testCmd, " ")

		if *useDockerCache {
			args = []string{"--use_docker_cache", cacheImage(t.flavor), t.flavor, testArgs}
		} else {
			// If there is no cache, we have to call 'make build' before each test.
			args = []string{t.flavor, t.bootstrapVersion, "make build && " + testArgs}
		}

		cmd = exec.Command(path.Join(dir, "docker/test/run.sh"), args...)
	} else {
		cmd = exec.Command(testCmd[0], testCmd[1:]...)
	}
	cmd.Dir = dir

	// Put everything in a unique dir, so we can copy and/or safely delete it.
	// Also try to make them use different port ranges
	// to mitigate failures due to zombie processes.
	cmd.Env = updateEnv(os.Environ(), map[string]string{
		"VTROOT":      "/vt/src/vitess.io/vitess",
		"VTDATAROOT":  dataDir,
		"VTPORTSTART": strconv.FormatInt(int64(getPortStart(100)), 10),
	})

	// Capture test output.
	buf := &bytes.Buffer{}
	cmd.Stdout = buf
	if *follow {
		cmd.Stdout = io.MultiWriter(cmd.Stdout, os.Stdout)
	}
	cmd.Stderr = cmd.Stdout

	// Run the test.
	done := make(chan error, 1)
	go func() {
		done <- cmd.Run()
	}()

	// Wait for it to finish.
	var runErr error
	timer := time.NewTimer(*timeout)
	defer timer.Stop()
	select {
	case runErr = <-done:
		if runErr == nil {
			t.pass++
		} else {
			t.fail++
		}
	case <-timer.C:
		t.logf("timeout exceeded")
		cmd.Process.Signal(syscall.SIGINT)
		t.fail++
		runErr = <-done
	}
	return buf.Bytes(), runErr
}

func (t *Test) logf(format string, v ...any) {
	if *runCount > 1 {
		log.Printf("%v.%v[%v/%v]: %v", t.flavor, t.name, t.runIndex+1, *runCount, fmt.Sprintf(format, v...))
	} else {
		log.Printf("%v.%v: %v", t.flavor, t.name, fmt.Sprintf(format, v...))
	}
}

func loadOneConfig(fileName string) (*Config, error) {
	config2 := &Config{}
	configData, err := os.ReadFile(fileName)
	if err != nil {
		log.Fatalf("Can't read config file %s: %v", fileName, err)
		return nil, err
	}
	if err := json.Unmarshal(configData, config2); err != nil {
		log.Fatalf("Can't parse config file: %v", err)
		return nil, err
	}
	return config2, nil

}

// Get test configs.
func loadConfig() (*Config, error) {
	config := &Config{Tests: make(map[string]*Test)}
	matches, _ := filepath.Glob("test/config*.json")
	for _, configFile := range matches {
		config2, err := loadOneConfig(configFile)
		if err != nil {
			return nil, err
		}
		if config2 == nil {
			log.Fatalf("could not load config file: %s", configFile)
		}
		for key, val := range config2.Tests {
			config.Tests[key] = val
		}
	}
	return config, nil
}

func main() {
	flag.Usage = func() {
		os.Stderr.WriteString(usage)
		os.Stderr.WriteString("\nOptions:\n")
		flag.PrintDefaults()
	}
	flag.Parse()

	// Sanity checks.
	if *docker {
		if *flavor == "all" {
			*flavor = flavors
		}
		if *flavor == "" {
			log.Fatalf("Must provide at least one -flavor when using -docker mode. Available flavors: all,%v", flavors)
		}
	}
	if *parallel < 1 {
		log.Fatalf("Invalid -parallel value: %v", *parallel)
	}
	if *parallel > 1 && !*docker {
		log.Fatalf("Can't use -parallel value > 1 when -docker=false")
	}
	if *useDockerCache && !*docker {
		log.Fatalf("Can't use -use_docker_cache when -docker=false")
	}

	startTime := time.Now()

	// Make output directory.
	outDir := path.Join("_test", fmt.Sprintf("%v.%v", startTime.Format("20060102-150405"), os.Getpid()))
	if err := os.MkdirAll(outDir, os.FileMode(0755)); err != nil {
		log.Fatalf("Can't create output directory: %v", err)
	}
	logFile, err := os.OpenFile(path.Join(outDir, "test.log"), os.O_RDWR|os.O_CREATE, 0644)
	if err != nil {
		log.Fatalf("Can't create log file: %v", err)
	}
	log.SetOutput(io.MultiWriter(os.Stderr, logFile))
	log.Printf("Output directory: %v", outDir)

	var config *Config
	if config, err = loadConfig(); err != nil {
		log.Fatalf("Could not load test config: %+v", err)
	}

	flavors := []string{"local"}

	if *docker && !*dryRun {
		log.Printf("Bootstrap flavor(s): %v", *flavor)

		flavors = strings.Split(*flavor, ",")

		// Re-pull image(s).
		if *pull {
			var wg sync.WaitGroup
			for _, flavor := range flavors {
				wg.Add(1)
				go func(flavor string) {
					defer wg.Done()
					image := "vitess/bootstrap:" + *bootstrapVersion + "-" + flavor
					pullTime := time.Now()
					log.Printf("Pulling %v...", image)
					cmd := exec.Command("docker", "pull", image)
					if out, err := cmd.CombinedOutput(); err != nil {
						log.Fatalf("Can't pull image %v: %v\n%s", image, err, out)
					}
					log.Printf("Image %v pulled in %v", image, round(time.Since(pullTime)))
				}(flavor)
			}
			wg.Wait()
		}
	} else {
		if vtDataRoot == "" {
			log.Fatalf("VTDATAROOT env var must be set in -docker=false mode. Make sure to source dev.env.")
		}
	}

	// Pick the tests to run.
	var testArgs []string
	testArgs, extraArgs = splitArgs(flag.Args(), "--")
	tests := selectedTests(testArgs, config)

	// Duplicate tests for run count.
	if *runCount > 1 {
		var dup []*Test
		for _, t := range tests {
			for i := 0; i < *runCount; i++ {
				// Make a copy, since they're pointers.
				test := *t
				test.runIndex = i
				dup = append(dup, &test)
			}
		}
		tests = dup
	}

	// Duplicate tests for flavors.
	var dup []*Test
	for _, flavor := range flavors {
		for _, t := range tests {
			test := *t
			test.flavor = flavor
			test.bootstrapVersion = *bootstrapVersion
			dup = append(dup, &test)
		}
	}
	tests = dup

	vtRoot := "."
	tmpDir := ""
	if *docker && !*dryRun {
		// Copy working repo to tmpDir.
		// This doesn't work outside Docker since it messes up GOROOT.
		tmpDir, err = os.MkdirTemp(os.TempDir(), "vt_")
		if err != nil {
			log.Fatalf("Can't create temp dir in %v", os.TempDir())
		}
		log.Printf("Copying working repo to temp dir %v", tmpDir)
		if out, err := exec.Command("cp", "-R", ".", tmpDir).CombinedOutput(); err != nil {
			log.Fatalf("Can't copy working repo to temp dir %v: %v: %s", tmpDir, err, out)
		}
		// The temp copy needs permissive access so the Docker user can read it.
		if out, err := exec.Command("chmod", "-R", "go=u", tmpDir).CombinedOutput(); err != nil {
			log.Printf("Can't set permissions on temp dir %v: %v: %s", tmpDir, err, out)
		}
		vtRoot = tmpDir
	} else if *skipBuild {
		log.Printf("Skipping build...")
	} else {
		// Since we're sharing the working dir, do the build once for all tests.
		log.Printf("Running make build...")
		if out, err := exec.Command("make", "build").CombinedOutput(); err != nil {
			log.Fatalf("make build failed: %v\n%s", err, out)
		}
	}

	if *useDockerCache {
		for _, flavor := range flavors {
			start := time.Now()
			log.Printf("Creating Docker cache image for flavor '%s'...", flavor)
			if out, err := exec.Command("docker/test/run.sh", "--create_docker_cache", cacheImage(flavor), flavor, *bootstrapVersion, "make build").CombinedOutput(); err != nil {
				log.Fatalf("Failed to create Docker cache image for flavor '%s': %v\n%s", flavor, err, out)
			}
			log.Printf("Creating Docker cache image took %v", round(time.Since(start)))
		}
	}

	// Keep stats for the overall run.
	var mu sync.Mutex
	failed := 0
	passed := 0
	flaky := 0

	// Listen for signals.
	sigchan := make(chan os.Signal, 1)
	signal.Notify(sigchan, syscall.SIGINT)

	// Run tests.
	stop := make(chan struct{}) // Close this to tell the runners to stop.
	done := make(chan struct{}) // This gets closed when all runners have stopped.
	next := make(chan *Test)    // The next test to run.
	var wg sync.WaitGroup

	// Send all tests into the channel.
	go func() {
		for _, test := range tests {
			next <- test
		}
		close(next)
	}()

	// Start the requested number of parallel runners.
	for i := 0; i < *parallel; i++ {
		wg.Add(1)
		go func() {
			defer wg.Done()

			for test := range next {
				tryMax := *retryMax
				if test.RetryMax != 0 {
					tryMax = test.RetryMax
				}
				for try := 1; ; try++ {
					select {
					case <-stop:
						test.logf("cancelled")
						return
					default:
					}

					if try > tryMax {
						// Every try failed.
						test.logf("retry limit exceeded")
						mu.Lock()
						failed++
						mu.Unlock()
						break
					}

					test.logf("running (try %v/%v)...", try, tryMax)

					// Make a unique VTDATAROOT.
					dataDir, err := os.MkdirTemp(vtDataRoot, "vt_")
					if err != nil {
						test.logf("Failed to create temporary subdir in VTDATAROOT: %v", vtDataRoot)
						mu.Lock()
						failed++
						mu.Unlock()
						break
					}

					// Run the test.
					start := time.Now()
					output, err := test.run(vtRoot, dataDir)
					duration := time.Since(start)

					// Save/print test output.
					if err != nil || *logPass {
						if *printLog && !*follow {
							test.logf("%s\n", output)
						}
						outFile := fmt.Sprintf("%v.%v-%v.%v.log", test.flavor, test.name, test.runIndex+1, try)
						outFilePath := path.Join(outDir, outFile)
						test.logf("saving test output to %v", outFilePath)
						if fileErr := os.WriteFile(outFilePath, output, os.FileMode(0644)); fileErr != nil {
							test.logf("WriteFile error: %v", fileErr)
						}
					}

					// Clean up the unique VTDATAROOT.
					if !*keepData {
						if err := os.RemoveAll(dataDir); err != nil {
							test.logf("WARNING: can't remove temporary VTDATAROOT: %v", err)
						}
					}

					if err != nil {
						// This try failed.
						test.logf("FAILED (try %v/%v) in %v: %v", try, tryMax, round(duration), err)
						mu.Lock()
						testFailed(test.name)
						mu.Unlock()
						continue
					}

					mu.Lock()
					testPassed(test.name, duration)

					if try == 1 {
						// Passed on the first try.
						test.logf("PASSED in %v", round(duration))
						passed++
					} else {
						// Passed, but not on the first try.
						test.logf("FLAKY (1/%v passed in %v)", try, round(duration))
						flaky++
						testFlaked(test.name, try)
					}
					mu.Unlock()
					break
				}
			}
		}()
	}

	// Close the done channel when all the runners stop.
	// This lets us select on wg.Wait().
	go func() {
		wg.Wait()
		close(done)
	}()

	// Stop the loop and kill child processes if we get a signal.
	select {
	case <-sigchan:
		log.Printf("interrupted: skip remaining tests and wait for current test to tear down")
		signal.Stop(sigchan)
		// Stop the test loop and wait for it to exit.
		// Running tests already get the SIGINT themselves.
		// We mustn't send it again, or it'll abort the teardown process too early.
		close(stop)
		<-done
	case <-done:
	}

	// Clean up temp dir.
	if tmpDir != "" {
		log.Printf("Removing temp dir %v", tmpDir)
		if err := os.RemoveAll(tmpDir); err != nil {
			log.Printf("Failed to remove temp dir: %v", err)
		}
	}
	// Remove temporary Docker cache image.
	if *useDockerCache {
		for _, flavor := range flavors {
			log.Printf("Removing temporary Docker cache image for flavor '%s'", flavor)
			if out, err := exec.Command("docker", "rmi", cacheImage(flavor)).CombinedOutput(); err != nil {
				log.Printf("WARNING: Failed to delete Docker cache image: %v\n%s", err, out)
			}
		}
	}

	// Print summary.
	log.Print(strings.Repeat("=", 60))
	for _, t := range tests {
		tname := t.flavor + "." + t.name
		switch {
		case t.pass > 0 && t.fail == 0:
			log.Printf("%-40s\tPASS", tname)
		case t.pass > 0 && t.fail > 0:
			log.Printf("%-40s\tFLAKY (%v/%v failed)", tname, t.fail, t.pass+t.fail)
		case t.pass == 0 && t.fail > 0:
			log.Printf("%-40s\tFAIL (%v tries)", tname, t.fail)
		case t.pass == 0 && t.fail == 0:
			log.Printf("%-40s\tSKIPPED", tname)
		}
	}
	log.Print(strings.Repeat("=", 60))
	skipped := len(tests) - passed - flaky - failed
	log.Printf("%v PASSED, %v FLAKY, %v FAILED, %v SKIPPED", passed, flaky, failed, skipped)
	log.Printf("Total time: %v", round(time.Since(startTime)))

	if failed > 0 || skipped > 0 {
		os.Exit(1)
	}
}

func updateEnv(orig []string, updates map[string]string) []string {
	var env []string
	for _, v := range orig {
		parts := strings.SplitN(v, "=", 2)
		if _, ok := updates[parts[0]]; !ok {
			env = append(env, v)
		}
	}
	for k, v := range updates {
		env = append(env, k+"="+v)
	}
	return env
}

// cacheImage returns the flavor-specific name of the Docker cache image.
func cacheImage(flavor string) string {
	return fmt.Sprintf("vitess/bootstrap:rm_%s_test_cache_do_NOT_push", flavor)
}

type Stats struct {
	TestStats map[string]TestStats
}

type TestStats struct {
	Pass, Fail, Flake int
	PassTime          time.Duration

	name string
}

func sendStats(values url.Values) {
	if *remoteStats != "" {
		log.Printf("Sending remote stats to %v", *remoteStats)
		resp, err := http.PostForm(*remoteStats, values)
		if err != nil {
			log.Printf("Can't send remote stats: %v", err)
		}
		defer resp.Body.Close()
	}
}

func testPassed(name string, passTime time.Duration) {
	sendStats(url.Values{
		"test":     {name},
		"result":   {"pass"},
		"duration": {passTime.String()},
	})
	updateTestStats(name, func(ts *TestStats) {
		totalTime := int64(ts.PassTime)*int64(ts.Pass) + int64(passTime)
		ts.Pass++
		ts.PassTime = time.Duration(totalTime / int64(ts.Pass))
	})
}

func testFailed(name string) {
	sendStats(url.Values{
		"test":   {name},
		"result": {"fail"},
	})
	updateTestStats(name, func(ts *TestStats) {
		ts.Fail++
	})
}

func testFlaked(name string, try int) {
	sendStats(url.Values{
		"test":   {name},
		"result": {"flake"},
		"try":    {strconv.FormatInt(int64(try), 10)},
	})
	updateTestStats(name, func(ts *TestStats) {
		ts.Flake += try - 1
	})
}

func updateTestStats(name string, update func(*TestStats)) {
	var stats Stats

	data, err := os.ReadFile(statsFileName)
	if err != nil {
		log.Print("Can't read stats file, starting new one.")
	} else {
		if err := json.Unmarshal(data, &stats); err != nil {
			log.Printf("Can't parse stats file: %v", err)
			return
		}
	}

	if stats.TestStats == nil {
		stats.TestStats = make(map[string]TestStats)
	}
	ts := stats.TestStats[name]
	update(&ts)
	stats.TestStats[name] = ts

	data, err = json.MarshalIndent(stats, "", "\t")
	if err != nil {
		log.Printf("Can't encode stats file: %v", err)
		return
	}
	if err := os.WriteFile(statsFileName, data, 0644); err != nil {
		log.Printf("Can't write stats file: %v", err)
	}
}

type ByPassTime []TestStats

func (a ByPassTime) Len() int           { return len(a) }
func (a ByPassTime) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
func (a ByPassTime) Less(i, j int) bool { return a[i].PassTime > a[j].PassTime }

func getTestsSorted(names []string, testMap map[string]*Test) []*Test {
	sort.Strings(names)
	var tests []*Test
	for _, name := range names {
		t := testMap[name]
		t.name = name
		tests = append(tests, t)
	}
	return tests
}

func selectedTests(args []string, config *Config) []*Test {
	var tests []*Test
	excludedTests := strings.Split(*exclude, ",")
	if *shard != "" {
		// Run the tests in a given shard.
		// This can be combined with positional args.
		var names []string
		for name, t := range config.Tests {
			if t.Shard == *shard && !t.Manual && (*exclude == "" || !t.hasAnyTag(excludedTests)) {
				t.name = name
				names = append(names, name)
			}
		}
		tests = getTestsSorted(names, config.Tests)
	}
	if len(args) > 0 {
		// Positional args for manual selection.
		for _, name := range args {
			t, ok := config.Tests[name]
			if !ok {
				tests := make([]string, len(config.Tests))

				i := 0
				for k := range config.Tests {
					tests[i] = k
					i++
				}

				sort.Strings(tests)

				log.Fatalf("Unknown test: %v\nAvailable tests are: %v", name, strings.Join(tests, ", "))
			}
			t.name = name
			tests = append(tests, t)
		}
	}
	if len(args) == 0 && *shard == "" {
		// Run all tests.
		var names []string
		for name, t := range config.Tests {
			if !t.Manual && (*tag == "" || t.hasTag(*tag)) && (*exclude == "" || !t.hasAnyTag(excludedTests)) {
				names = append(names, name)
			}
		}
		tests = getTestsSorted(names, config.Tests)
	}
	return tests
}

var (
	port      = 16000
	portMutex sync.Mutex
)

func getPortStart(size int) int {
	portMutex.Lock()
	defer portMutex.Unlock()

	start := port
	port += size
	return start
}

// splitArgs splits a list of args at the first appearance of tok.
func splitArgs(all []string, tok string) (args, extraArgs []string) {
	extra := false
	for _, arg := range all {
		if extra {
			extraArgs = append(extraArgs, arg)
			continue
		}
		if arg == tok {
			extra = true
			continue
		}
		args = append(args, arg)
	}
	return
}

func round(d time.Duration) time.Duration {
	return d.Round(100 * time.Millisecond)
}