vendor/google.golang.org/grpc/internal/idle/idle.go - shac-project/shac - Git at Google

 /*
  *
  * Copyright 2023 gRPC 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.
  *
  */

 // Package idle contains a component for managing idleness (entering and exiting)
 // based on RPC activity.
 package idle

 import (
 	"fmt"
 	"math"
 	"sync"
 	"sync/atomic"
 	"time"
 )

 // For overriding in unit tests.
 var timeAfterFunc = func(d time.Duration, f func()) *time.Timer {
 	return time.AfterFunc(d, f)
 }

 // Enforcer is the functionality provided by grpc.ClientConn to enter
 // and exit from idle mode.
 type Enforcer interface {
 	ExitIdleMode() error
 	EnterIdleMode()
 }

 // Manager implements idleness detection and calls the configured Enforcer to
 // enter/exit idle mode when appropriate.  Must be created by NewManager.
 type Manager struct {
 	// State accessed atomically.
 	lastCallEndTime           int64 // Unix timestamp in nanos; time when the most recent RPC completed.
 	activeCallsCount          int32 // Count of active RPCs; -math.MaxInt32 means channel is idle or is trying to get there.
 	activeSinceLastTimerCheck int32 // Boolean; True if there was an RPC since the last timer callback.
 	closed                    int32 // Boolean; True when the manager is closed.

 	// Can be accessed without atomics or mutex since these are set at creation
 	// time and read-only after that.
 	enforcer Enforcer // Functionality provided by grpc.ClientConn.
 	timeout  time.Duration

 	// idleMu is used to guarantee mutual exclusion in two scenarios:
 	// - Opposing intentions:
 	//   - a: Idle timeout has fired and handleIdleTimeout() is trying to put
 	//     the channel in idle mode because the channel has been inactive.
 	//   - b: At the same time an RPC is made on the channel, and OnCallBegin()
 	//     is trying to prevent the channel from going idle.
 	// - Competing intentions:
 	//   - The channel is in idle mode and there are multiple RPCs starting at
 	//     the same time, all trying to move the channel out of idle. Only one
 	//     of them should succeed in doing so, while the other RPCs should
 	//     piggyback on the first one and be successfully handled.
 	idleMu       sync.RWMutex
 	actuallyIdle bool
 	timer        *time.Timer
 }

 // NewManager creates a new idleness manager implementation for the
 // given idle timeout.  It begins in idle mode.
 func NewManager(enforcer Enforcer, timeout time.Duration) *Manager {
 	return &Manager{
 		enforcer:         enforcer,
 		timeout:          timeout,
 		actuallyIdle:     true,
 		activeCallsCount: -math.MaxInt32,
 	}
 }

 // resetIdleTimerLocked resets the idle timer to the given duration.  Called
 // when exiting idle mode or when the timer fires and we need to reset it.
 func (m *Manager) resetIdleTimerLocked(d time.Duration) {
 	if m.isClosed() || m.timeout == 0 || m.actuallyIdle {
 		return
 	}

 	// It is safe to ignore the return value from Reset() because this method is
 	// only ever called from the timer callback or when exiting idle mode.
 	if m.timer != nil {
 		m.timer.Stop()
 	}
 	m.timer = timeAfterFunc(d, m.handleIdleTimeout)
 }

 func (m *Manager) resetIdleTimer(d time.Duration) {
 	m.idleMu.Lock()
 	defer m.idleMu.Unlock()
 	m.resetIdleTimerLocked(d)
 }

 // handleIdleTimeout is the timer callback that is invoked upon expiry of the
 // configured idle timeout. The channel is considered inactive if there are no
 // ongoing calls and no RPC activity since the last time the timer fired.
 func (m *Manager) handleIdleTimeout() {
 	if m.isClosed() {
 		return
 	}

 	if atomic.LoadInt32(&m.activeCallsCount) > 0 {
 		m.resetIdleTimer(m.timeout)
 		return
 	}

 	// There has been activity on the channel since we last got here. Reset the
 	// timer and return.
 	if atomic.LoadInt32(&m.activeSinceLastTimerCheck) == 1 {
 		// Set the timer to fire after a duration of idle timeout, calculated
 		// from the time the most recent RPC completed.
 		atomic.StoreInt32(&m.activeSinceLastTimerCheck, 0)
 		m.resetIdleTimer(time.Duration(atomic.LoadInt64(&m.lastCallEndTime)-time.Now().UnixNano()) + m.timeout)
 		return
 	}

 	// Now that we've checked that there has been no activity, attempt to enter
 	// idle mode, which is very likely to succeed.
 	if m.tryEnterIdleMode() {
 		// Successfully entered idle mode. No timer needed until we exit idle.
 		return
 	}

 	// Failed to enter idle mode due to a concurrent RPC that kept the channel
 	// active, or because of an error from the channel. Undo the attempt to
 	// enter idle, and reset the timer to try again later.
 	m.resetIdleTimer(m.timeout)
 }

 // tryEnterIdleMode instructs the channel to enter idle mode. But before
 // that, it performs a last minute check to ensure that no new RPC has come in,
 // making the channel active.
 //
 // Return value indicates whether or not the channel moved to idle mode.
 //
 // Holds idleMu which ensures mutual exclusion with exitIdleMode.
 func (m *Manager) tryEnterIdleMode() bool {
 	// Setting the activeCallsCount to -math.MaxInt32 indicates to OnCallBegin()
 	// that the channel is either in idle mode or is trying to get there.
 	if !atomic.CompareAndSwapInt32(&m.activeCallsCount, 0, -math.MaxInt32) {
 		// This CAS operation can fail if an RPC started after we checked for
 		// activity in the timer handler, or one was ongoing from before the
 		// last time the timer fired, or if a test is attempting to enter idle
 		// mode without checking.  In all cases, abort going into idle mode.
 		return false
 	}
 	// N.B. if we fail to enter idle mode after this, we must re-add
 	// math.MaxInt32 to m.activeCallsCount.

 	m.idleMu.Lock()
 	defer m.idleMu.Unlock()

 	if atomic.LoadInt32(&m.activeCallsCount) != -math.MaxInt32 {
 		// We raced and lost to a new RPC. Very rare, but stop entering idle.
 		atomic.AddInt32(&m.activeCallsCount, math.MaxInt32)
 		return false
 	}
 	if atomic.LoadInt32(&m.activeSinceLastTimerCheck) == 1 {
 		// A very short RPC could have come in (and also finished) after we
 		// checked for calls count and activity in handleIdleTimeout(), but
 		// before the CAS operation. So, we need to check for activity again.
 		atomic.AddInt32(&m.activeCallsCount, math.MaxInt32)
 		return false
 	}

 	// No new RPCs have come in since we set the active calls count value to
 	// -math.MaxInt32. And since we have the lock, it is safe to enter idle mode
 	// unconditionally now.
 	m.enforcer.EnterIdleMode()
 	m.actuallyIdle = true
 	return true
 }

 func (m *Manager) EnterIdleModeForTesting() {
 	m.tryEnterIdleMode()
 }

 // OnCallBegin is invoked at the start of every RPC.
 func (m *Manager) OnCallBegin() error {
 	if m.isClosed() {
 		return nil
 	}

 	if atomic.AddInt32(&m.activeCallsCount, 1) > 0 {
 		// Channel is not idle now. Set the activity bit and allow the call.
 		atomic.StoreInt32(&m.activeSinceLastTimerCheck, 1)
 		return nil
 	}

 	// Channel is either in idle mode or is in the process of moving to idle
 	// mode. Attempt to exit idle mode to allow this RPC.
 	if err := m.ExitIdleMode(); err != nil {
 		// Undo the increment to calls count, and return an error causing the
 		// RPC to fail.
 		atomic.AddInt32(&m.activeCallsCount, -1)
 		return err
 	}

 	atomic.StoreInt32(&m.activeSinceLastTimerCheck, 1)
 	return nil
 }

 // ExitIdleMode instructs m to call the enforcer's ExitIdleMode and update m's
 // internal state.
 func (m *Manager) ExitIdleMode() error {
 	// Holds idleMu which ensures mutual exclusion with tryEnterIdleMode.
 	m.idleMu.Lock()
 	defer m.idleMu.Unlock()

 	if m.isClosed() || !m.actuallyIdle {
 		// This can happen in three scenarios:
 		// - handleIdleTimeout() set the calls count to -math.MaxInt32 and called
 		//   tryEnterIdleMode(). But before the latter could grab the lock, an RPC
 		//   came in and OnCallBegin() noticed that the calls count is negative.
 		// - Channel is in idle mode, and multiple new RPCs come in at the same
 		//   time, all of them notice a negative calls count in OnCallBegin and get
 		//   here. The first one to get the lock would got the channel to exit idle.
 		// - Channel is not in idle mode, and the user calls Connect which calls
 		//   m.ExitIdleMode.
 		//
 		// In any case, there is nothing to do here.
 		return nil
 	}

 	if err := m.enforcer.ExitIdleMode(); err != nil {
 		return fmt.Errorf("failed to exit idle mode: %w", err)
 	}

 	// Undo the idle entry process. This also respects any new RPC attempts.
 	atomic.AddInt32(&m.activeCallsCount, math.MaxInt32)
 	m.actuallyIdle = false

 	// Start a new timer to fire after the configured idle timeout.
 	m.resetIdleTimerLocked(m.timeout)
 	return nil
 }

 // OnCallEnd is invoked at the end of every RPC.
 func (m *Manager) OnCallEnd() {
 	if m.isClosed() {
 		return
 	}

 	// Record the time at which the most recent call finished.
 	atomic.StoreInt64(&m.lastCallEndTime, time.Now().UnixNano())

 	// Decrement the active calls count. This count can temporarily go negative
 	// when the timer callback is in the process of moving the channel to idle
 	// mode, but one or more RPCs come in and complete before the timer callback
 	// can get done with the process of moving to idle mode.
 	atomic.AddInt32(&m.activeCallsCount, -1)
 }

 func (m *Manager) isClosed() bool {
 	return atomic.LoadInt32(&m.closed) == 1
 }

 func (m *Manager) Close() {
 	atomic.StoreInt32(&m.closed, 1)

 	m.idleMu.Lock()
 	if m.timer != nil {
 		m.timer.Stop()
 		m.timer = nil
 	}
 	m.idleMu.Unlock()
 }
	/*
	*
	* Copyright 2023 gRPC 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.
	*
	*/

	// Package idle contains a component for managing idleness (entering and exiting)
	// based on RPC activity.
	package idle

	import (
	"fmt"
	"math"
	"sync"
	"sync/atomic"
	"time"
	)

	// For overriding in unit tests.
	var timeAfterFunc = func(d time.Duration, f func()) *time.Timer {
	return time.AfterFunc(d, f)
	}

	// Enforcer is the functionality provided by grpc.ClientConn to enter
	// and exit from idle mode.
	type Enforcer interface {
	ExitIdleMode() error
	EnterIdleMode()
	}

	// Manager implements idleness detection and calls the configured Enforcer to
	// enter/exit idle mode when appropriate. Must be created by NewManager.
	type Manager struct {
	// State accessed atomically.
	lastCallEndTime int64 // Unix timestamp in nanos; time when the most recent RPC completed.
	activeCallsCount int32 // Count of active RPCs; -math.MaxInt32 means channel is idle or is trying to get there.
	activeSinceLastTimerCheck int32 // Boolean; True if there was an RPC since the last timer callback.
	closed int32 // Boolean; True when the manager is closed.

	// Can be accessed without atomics or mutex since these are set at creation
	// time and read-only after that.
	enforcer Enforcer // Functionality provided by grpc.ClientConn.
	timeout time.Duration

	// idleMu is used to guarantee mutual exclusion in two scenarios:
	// - Opposing intentions:
	// - a: Idle timeout has fired and handleIdleTimeout() is trying to put
	// the channel in idle mode because the channel has been inactive.
	// - b: At the same time an RPC is made on the channel, and OnCallBegin()
	// is trying to prevent the channel from going idle.
	// - Competing intentions:
	// - The channel is in idle mode and there are multiple RPCs starting at
	// the same time, all trying to move the channel out of idle. Only one
	// of them should succeed in doing so, while the other RPCs should
	// piggyback on the first one and be successfully handled.
	idleMu sync.RWMutex
	actuallyIdle bool
	timer *time.Timer
	}

	// NewManager creates a new idleness manager implementation for the
	// given idle timeout. It begins in idle mode.
	func NewManager(enforcer Enforcer, timeout time.Duration) *Manager {
	return &Manager{
	enforcer: enforcer,
	timeout: timeout,
	actuallyIdle: true,
	activeCallsCount: -math.MaxInt32,
	}
	}

	// resetIdleTimerLocked resets the idle timer to the given duration. Called
	// when exiting idle mode or when the timer fires and we need to reset it.
	func (m *Manager) resetIdleTimerLocked(d time.Duration) {
	if m.isClosed() \|\| m.timeout == 0 \|\| m.actuallyIdle {
	return
	}

	// It is safe to ignore the return value from Reset() because this method is
	// only ever called from the timer callback or when exiting idle mode.
	if m.timer != nil {
	m.timer.Stop()
	}
	m.timer = timeAfterFunc(d, m.handleIdleTimeout)
	}

	func (m *Manager) resetIdleTimer(d time.Duration) {
	m.idleMu.Lock()
	defer m.idleMu.Unlock()
	m.resetIdleTimerLocked(d)
	}

	// handleIdleTimeout is the timer callback that is invoked upon expiry of the
	// configured idle timeout. The channel is considered inactive if there are no
	// ongoing calls and no RPC activity since the last time the timer fired.
	func (m *Manager) handleIdleTimeout() {
	if m.isClosed() {
	return
	}

	if atomic.LoadInt32(&m.activeCallsCount) > 0 {
	m.resetIdleTimer(m.timeout)
	return
	}

	// There has been activity on the channel since we last got here. Reset the
	// timer and return.
	if atomic.LoadInt32(&m.activeSinceLastTimerCheck) == 1 {
	// Set the timer to fire after a duration of idle timeout, calculated
	// from the time the most recent RPC completed.
	atomic.StoreInt32(&m.activeSinceLastTimerCheck, 0)
	m.resetIdleTimer(time.Duration(atomic.LoadInt64(&m.lastCallEndTime)-time.Now().UnixNano()) + m.timeout)
	return
	}

	// Now that we've checked that there has been no activity, attempt to enter
	// idle mode, which is very likely to succeed.
	if m.tryEnterIdleMode() {
	// Successfully entered idle mode. No timer needed until we exit idle.
	return
	}

	// Failed to enter idle mode due to a concurrent RPC that kept the channel
	// active, or because of an error from the channel. Undo the attempt to
	// enter idle, and reset the timer to try again later.
	m.resetIdleTimer(m.timeout)
	}

	// tryEnterIdleMode instructs the channel to enter idle mode. But before
	// that, it performs a last minute check to ensure that no new RPC has come in,
	// making the channel active.
	//
	// Return value indicates whether or not the channel moved to idle mode.
	//
	// Holds idleMu which ensures mutual exclusion with exitIdleMode.
	func (m *Manager) tryEnterIdleMode() bool {
	// Setting the activeCallsCount to -math.MaxInt32 indicates to OnCallBegin()
	// that the channel is either in idle mode or is trying to get there.
	if !atomic.CompareAndSwapInt32(&m.activeCallsCount, 0, -math.MaxInt32) {
	// This CAS operation can fail if an RPC started after we checked for
	// activity in the timer handler, or one was ongoing from before the
	// last time the timer fired, or if a test is attempting to enter idle
	// mode without checking. In all cases, abort going into idle mode.
	return false
	}
	// N.B. if we fail to enter idle mode after this, we must re-add
	// math.MaxInt32 to m.activeCallsCount.

	m.idleMu.Lock()
	defer m.idleMu.Unlock()

	if atomic.LoadInt32(&m.activeCallsCount) != -math.MaxInt32 {
	// We raced and lost to a new RPC. Very rare, but stop entering idle.
	atomic.AddInt32(&m.activeCallsCount, math.MaxInt32)
	return false
	}
	if atomic.LoadInt32(&m.activeSinceLastTimerCheck) == 1 {
	// A very short RPC could have come in (and also finished) after we
	// checked for calls count and activity in handleIdleTimeout(), but
	// before the CAS operation. So, we need to check for activity again.
	atomic.AddInt32(&m.activeCallsCount, math.MaxInt32)
	return false
	}

	// No new RPCs have come in since we set the active calls count value to
	// -math.MaxInt32. And since we have the lock, it is safe to enter idle mode
	// unconditionally now.
	m.enforcer.EnterIdleMode()
	m.actuallyIdle = true
	return true
	}

	func (m *Manager) EnterIdleModeForTesting() {
	m.tryEnterIdleMode()
	}

	// OnCallBegin is invoked at the start of every RPC.
	func (m *Manager) OnCallBegin() error {
	if m.isClosed() {
	return nil
	}

	if atomic.AddInt32(&m.activeCallsCount, 1) > 0 {
	// Channel is not idle now. Set the activity bit and allow the call.
	atomic.StoreInt32(&m.activeSinceLastTimerCheck, 1)
	return nil
	}

	// Channel is either in idle mode or is in the process of moving to idle
	// mode. Attempt to exit idle mode to allow this RPC.
	if err := m.ExitIdleMode(); err != nil {
	// Undo the increment to calls count, and return an error causing the
	// RPC to fail.
	atomic.AddInt32(&m.activeCallsCount, -1)
	return err
	}

	atomic.StoreInt32(&m.activeSinceLastTimerCheck, 1)
	return nil
	}

	// ExitIdleMode instructs m to call the enforcer's ExitIdleMode and update m's
	// internal state.
	func (m *Manager) ExitIdleMode() error {
	// Holds idleMu which ensures mutual exclusion with tryEnterIdleMode.
	m.idleMu.Lock()
	defer m.idleMu.Unlock()

	if m.isClosed() \|\| !m.actuallyIdle {
	// This can happen in three scenarios:
	// - handleIdleTimeout() set the calls count to -math.MaxInt32 and called
	// tryEnterIdleMode(). But before the latter could grab the lock, an RPC
	// came in and OnCallBegin() noticed that the calls count is negative.
	// - Channel is in idle mode, and multiple new RPCs come in at the same
	// time, all of them notice a negative calls count in OnCallBegin and get
	// here. The first one to get the lock would got the channel to exit idle.
	// - Channel is not in idle mode, and the user calls Connect which calls
	// m.ExitIdleMode.
	//
	// In any case, there is nothing to do here.
	return nil
	}

	if err := m.enforcer.ExitIdleMode(); err != nil {
	return fmt.Errorf("failed to exit idle mode: %w", err)
	}

	// Undo the idle entry process. This also respects any new RPC attempts.
	atomic.AddInt32(&m.activeCallsCount, math.MaxInt32)
	m.actuallyIdle = false

	// Start a new timer to fire after the configured idle timeout.
	m.resetIdleTimerLocked(m.timeout)
	return nil
	}

	// OnCallEnd is invoked at the end of every RPC.
	func (m *Manager) OnCallEnd() {
	if m.isClosed() {
	return
	}

	// Record the time at which the most recent call finished.
	atomic.StoreInt64(&m.lastCallEndTime, time.Now().UnixNano())

	// Decrement the active calls count. This count can temporarily go negative
	// when the timer callback is in the process of moving the channel to idle
	// mode, but one or more RPCs come in and complete before the timer callback
	// can get done with the process of moving to idle mode.
	atomic.AddInt32(&m.activeCallsCount, -1)
	}

	func (m *Manager) isClosed() bool {
	return atomic.LoadInt32(&m.closed) == 1
	}

	func (m *Manager) Close() {
	atomic.StoreInt32(&m.closed, 1)

	m.idleMu.Lock()
	if m.timer != nil {
	m.timer.Stop()
	m.timer = nil
	}
	m.idleMu.Unlock()
	}