Golang parallel.NewTry函数代码示例

func (*trySuite) TestOneSuccess(c *gc.C) {
	try := parallel.NewTry(0, nil)
	try.Start(tryFunc(0, result("hello"), nil))
	val, err := try.Result()
	c.Assert(err, gc.IsNil)
	c.Assert(val, gc.Equals, result("hello"))
}

func (*trySuite) TestExtraResultsAreClosed(c *gc.C) {
	try := parallel.NewTry(0, nil)
	begin := make([]chan struct{}, 4)
	results := make([]*closeResult, len(begin))
	for i := range begin {
		begin[i] = make(chan struct{})
		results[i] = &closeResult{make(chan struct{})}
		i := i
		try.Start(func(<-chan struct{}) (io.Closer, error) {
			<-begin[i]
			return results[i], nil
		})
	}
	begin[0] <- struct{}{}
	val, err := try.Result()
	c.Assert(err, gc.IsNil)
	c.Assert(val, gc.Equals, results[0])

	timeout := time.After(shortWait)
	for i, r := range results[1:] {
		begin[i+1] <- struct{}{}
		select {
		case <-r.closed:
		case <-timeout:
			c.Fatalf("timed out waiting for close")
		}
	}
	select {
	case <-results[0].closed:
		c.Fatalf("result was inappropriately closed")
	case <-time.After(shortWait):
	}
}

func (*trySuite) TestMaxParallel(c *gc.C) {
	try := parallel.NewTry(3, nil)
	var (
		mu    sync.Mutex
		count int
		max   int
	)

	for i := 0; i < 10; i++ {
		try.Start(func(<-chan struct{}) (io.Closer, error) {
			mu.Lock()
			if count++; count > max {
				max = count
			}
			c.Check(count, gc.Not(jc.GreaterThan), 3)
			mu.Unlock()
			time.Sleep(20 * time.Millisecond)
			mu.Lock()
			count--
			mu.Unlock()
			return result("hello"), nil
		})
	}
	r, err := try.Result()
	c.Assert(err, gc.IsNil)
	c.Assert(r, gc.Equals, result("hello"))
	mu.Lock()
	defer mu.Unlock()
	c.Assert(max, gc.Equals, 3)
}

func (*trySuite) TestOutOfOrderResults(c *gc.C) {
	try := parallel.NewTry(0, nil)
	try.Start(tryFunc(50*time.Millisecond, result("first"), nil))
	try.Start(tryFunc(10*time.Millisecond, result("second"), nil))
	r, err := try.Result()
	c.Assert(err, gc.IsNil)
	c.Assert(r, gc.Equals, result("second"))
}

func (*trySuite) TestCloseTwice(c *gc.C) {
	try := parallel.NewTry(0, nil)
	try.Close()
	try.Close()
	val, err := try.Result()
	c.Assert(val, gc.IsNil)
	c.Assert(err, gc.IsNil)
}

func (*trySuite) TestStartReturnsErrorAfterClose(c *gc.C) {
	try := parallel.NewTry(0, nil)
	expectErr := errors.New("foo")
	err := try.Start(tryFunc(0, nil, expectErr))
	c.Assert(err, gc.IsNil)
	try.Close()
	err = try.Start(tryFunc(0, result("goodbye"), nil))
	c.Assert(err, gc.Equals, parallel.ErrClosed)
	// Wait for the first try to deliver its result
	time.Sleep(shortWait)
	try.Kill()
	err = try.Wait()
	c.Assert(err, gc.Equals, expectErr)
}

func (*trySuite) TestTriesAreStopped(c *gc.C) {
	try := parallel.NewTry(0, nil)
	stopped := make(chan struct{})
	try.Start(func(stop <-chan struct{}) (io.Closer, error) {
		<-stop
		stopped <- struct{}{}
		return nil, parallel.ErrStopped
	})
	try.Start(tryFunc(0, result("hello"), nil))
	val, err := try.Result()
	c.Assert(err, gc.IsNil)
	c.Assert(val, gc.Equals, result("hello"))

	select {
	case <-stopped:
	case <-time.After(longWait):
		c.Fatalf("timed out waiting for stop")
	}
}

// Connect establishes a websocket connection to the API server using
// the Info, API path tail and (optional) request headers provided. If
// multiple API addresses are provided in Info they will be tried
// concurrently - the first successful connection wins.
//
// The path tail may be blank, in which case the default value will be
// used. Otherwise, it must start with a "/".
func Connect(info *Info, pathTail string, header http.Header, opts DialOpts) (*websocket.Conn, error) {
	if len(info.Addrs) == 0 {
		return nil, errors.New("no API addresses to connect to")
	}
	if pathTail != "" && !strings.HasPrefix(pathTail, "/") {
		return nil, errors.New(`path tail must start with "/"`)
	}

	pool := x509.NewCertPool()
	xcert, err := cert.ParseCert(info.CACert)
	if err != nil {
		return nil, errors.Annotate(err, "cert pool creation failed")
	}
	pool.AddCert(xcert)

	path := makeAPIPath(info.EnvironTag.Id(), pathTail)

	// Dial all addresses at reasonable intervals.
	try := parallel.NewTry(0, nil)
	defer try.Kill()
	for _, addr := range info.Addrs {
		err := dialWebsocket(addr, path, header, opts, pool, try)
		if err == parallel.ErrStopped {
			break
		}
		if err != nil {
			return nil, errors.Trace(err)
		}
		select {
		case <-time.After(opts.DialAddressInterval):
		case <-try.Dead():
		}
	}
	try.Close()
	result, err := try.Result()
	if err != nil {
		return nil, errors.Trace(err)
	}
	conn := result.(*websocket.Conn)
	logger.Infof("connection established to %q", conn.RemoteAddr())
	return conn, nil
}

func (*trySuite) TestOneFailure(c *gc.C) {
	try := parallel.NewTry(0, nil)
	expectErr := errors.New("foo")
	err := try.Start(tryFunc(0, nil, expectErr))
	c.Assert(err, gc.IsNil)
	select {
	case <-try.Dead():
		c.Fatalf("try died before it should")
	case <-time.After(shortWait):
	}
	try.Close()
	select {
	case <-try.Dead():
	case <-time.After(longWait):
		c.Fatalf("timed out waiting for Try to complete")
	}
	val, err := try.Result()
	c.Assert(val, gc.IsNil)
	c.Assert(err, gc.Equals, expectErr)
}

func (*trySuite) TestAllConcurrent(c *gc.C) {
	try := parallel.NewTry(0, nil)
	started := make(chan chan struct{})
	for i := 0; i < 10; i++ {
		try.Start(func(<-chan struct{}) (io.Closer, error) {
			reply := make(chan struct{})
			started <- reply
			<-reply
			return result("hello"), nil
		})
	}
	timeout := time.After(longWait)
	for i := 0; i < 10; i++ {
		select {
		case reply := <-started:
			reply <- struct{}{}
		case <-timeout:
			c.Fatalf("timed out")
		}
	}
}

func (*trySuite) TestEverything(c *gc.C) {
	try := parallel.NewTry(5, gradedErrorCombine)
	tries := []struct {
		startAt time.Duration
		wait    time.Duration
		val     result
		err     error
	}{{
		wait: 30 * time.Millisecond,
		err:  gradedError(3),
	}, {
		startAt: 10 * time.Millisecond,
		wait:    20 * time.Millisecond,
		val:     result("result 1"),
	}, {
		startAt: 20 * time.Millisecond,
		wait:    10 * time.Millisecond,
		val:     result("result 2"),
	}, {
		startAt: 20 * time.Millisecond,
		wait:    5 * time.Second,
		val:     "delayed result",
	}, {
		startAt: 5 * time.Millisecond,
		err:     gradedError(4),
	}}
	for _, t := range tries {
		t := t
		go func() {
			time.Sleep(t.startAt)
			try.Start(tryFunc(t.wait, t.val, t.err))
		}()
	}
	val, err := try.Result()
	if val != result("result 1") && val != result("result 2") {
		c.Errorf(`expected "result 1" or "result 2" got %#v`, val)
	}
	c.Assert(err, gc.IsNil)
}

// connectWebsocket establishes a websocket connection to the RPC
// API websocket on the API server using Info. If multiple API addresses
// are provided in Info they will be tried concurrently - the first successful
// connection wins.
//
// It also returns the TLS configuration that it has derived from the Info.
func connectWebsocket(info *Info, opts DialOpts) (*websocket.Conn, *tls.Config, error) {
	if len(info.Addrs) == 0 {
		return nil, nil, errors.New("no API addresses to connect to")
	}
	tlsConfig, err := tlsConfigForCACert(info.CACert)
	if err != nil {
		return nil, nil, errors.Annotatef(err, "cannot make TLS configuration")
	}
	path := "/"
	if info.EnvironTag.Id() != "" {
		path = apiPath(info.EnvironTag, "/api")
	}

	// Dial all addresses at reasonable intervals.
	try := parallel.NewTry(0, nil)
	defer try.Kill()
	for _, addr := range info.Addrs {
		err := dialWebsocket(addr, path, opts, tlsConfig, try)
		if err == parallel.ErrStopped {
			break
		}
		if err != nil {
			return nil, nil, errors.Trace(err)
		}
		select {
		case <-time.After(opts.DialAddressInterval):
		case <-try.Dead():
		}
	}
	try.Close()
	result, err := try.Result()
	if err != nil {
		return nil, nil, errors.Trace(err)
	}
	conn := result.(*websocket.Conn)
	logger.Infof("connection established to %q", conn.RemoteAddr())
	return conn, tlsConfig, nil
}

func (*trySuite) TestErrorCombine(c *gc.C) {
	// Use maxParallel=1 to guarantee that all errors are processed sequentially.
	try := parallel.NewTry(1, func(err0, err1 error) error {
		if err0 == nil {
			err0 = &multiError{}
		}
		err0.(*multiError).errs = append(err0.(*multiError).errs, int(err1.(gradedError)))
		return err0
	})
	errors := []gradedError{3, 2, 4, 0, 5, 5, 3}
	for _, err := range errors {
		err := err
		try.Start(func(<-chan struct{}) (io.Closer, error) {
			return nil, err
		})
	}
	try.Close()
	val, err := try.Result()
	c.Assert(val, gc.IsNil)
	grades := err.(*multiError).errs
	sort.Ints(grades)
	c.Assert(grades, gc.DeepEquals, []int{0, 2, 3, 3, 4, 5, 5})
}

// dialWebsocketMulti dials a websocket with one of the provided addresses, the
// specified URL path, TLS configuration, and dial options. Each of the
// specified addresses will be attempted concurrently, and the first
// successful connection will be returned.
func dialWebsocketMulti(addrs []string, path string, tlsConfig *tls.Config, opts DialOpts) (*websocket.Conn, error) {
	// Dial all addresses at reasonable intervals.
	try := parallel.NewTry(0, nil)
	defer try.Kill()
	for _, addr := range addrs {
		err := startDialWebsocket(try, addr, path, opts, tlsConfig)
		if err == parallel.ErrStopped {
			break
		}
		if err != nil {
			return nil, errors.Trace(err)
		}
		select {
		case <-time.After(opts.DialAddressInterval):
		case <-try.Dead():
		}
	}
	try.Close()
	result, err := try.Result()
	if err != nil {
		return nil, errors.Trace(err)
	}
	return result.(*websocket.Conn), nil
}

// newAPIFromStore implements the bulk of NewAPIClientFromName
// but is separate for testing purposes.
func newAPIFromStore(envName string, store configstore.Storage, apiOpen apiOpenFunc) (apiState, error) {
	// Try to read the default environment configuration file.
	// If it doesn't exist, we carry on in case
	// there's some environment info for that environment.
	// This enables people to copy environment files
	// into their .juju/environments directory and have
	// them be directly useful with no further configuration changes.
	envs, err := environs.ReadEnvirons("")
	if err == nil {
		if envName == "" {
			envName = envs.Default
		}
		if envName == "" {
			return nil, fmt.Errorf("no default environment found")
		}
	} else if !environs.IsNoEnv(err) {
		return nil, err
	}

	// Try to connect to the API concurrently using two different
	// possible sources of truth for the API endpoint. Our
	// preference is for the API endpoint cached in the API info,
	// because we know that without needing to access any remote
	// provider. However, the addresses stored there may no longer
	// be current (and the network connection may take a very long
	// time to time out) so we also try to connect using information
	// found from the provider. We only start to make that
	// connection after some suitable delay, so that in the
	// hopefully usual case, we will make the connection to the API
	// and never hit the provider. By preference we use provider
	// attributes from the config store, but for backward
	// compatibility reasons, we fall back to information from
	// ReadEnvirons if that does not exist.
	chooseError := func(err0, err1 error) error {
		if err0 == nil {
			return err1
		}
		if errorImportance(err0) < errorImportance(err1) {
			err0, err1 = err1, err0
		}
		logger.Warningf("discarding API open error: %v", err1)
		return err0
	}
	try := parallel.NewTry(0, chooseError)

	info, err := store.ReadInfo(envName)
	if err != nil && !errors.IsNotFound(err) {
		return nil, err
	}
	var delay time.Duration
	if info != nil && len(info.APIEndpoint().Addresses) > 0 {
		logger.Debugf(
			"trying cached API connection settings - endpoints %v",
			info.APIEndpoint().Addresses,
		)
		try.Start(func(stop <-chan struct{}) (io.Closer, error) {
			return apiInfoConnect(info, apiOpen, stop)
		})
		// Delay the config connection until we've spent
		// some time trying to connect to the cached info.
		delay = providerConnectDelay
	} else {
		logger.Debugf("no cached API connection settings found")
	}
	try.Start(func(stop <-chan struct{}) (io.Closer, error) {
		cfg, err := getConfig(info, envs, envName)
		if err != nil {
			return nil, err
		}
		return apiConfigConnect(cfg, apiOpen, stop, delay, environInfoUserTag(info))
	})
	try.Close()
	val0, err := try.Result()
	if err != nil {
		if ierr, ok := err.(*infoConnectError); ok {
			// lose error encapsulation:
			err = ierr.error
		}
		return nil, err
	}

	st := val0.(apiState)
	addrConnectedTo, err := serverAddress(st.Addr())
	if err != nil {
		return nil, err
	}
	// Even though we are about to update API addresses based on
	// APIHostPorts in cacheChangedAPIInfo, we first cache the
	// addresses based on the provider lookup. This is because older API
	// servers didn't return their HostPort information on Login, and we
	// still want to cache our connection information to them.
	if cachedInfo, ok := st.(apiStateCachedInfo); ok {
		st = cachedInfo.apiState
		if cachedInfo.cachedInfo != nil && info != nil {
			// Cache the connection settings only if we used the
			// environment config, but any errors are just logged
			// as warnings, because they're not fatal.
			err = cacheAPIInfo(st, info, cachedInfo.cachedInfo)
//.........这里部分代码省略.........