summaryrefslogtreecommitdiff
path: root/vendor/google.golang.org/grpc/internal/idle/idle.go
diff options
context:
space:
mode:
authorLibravatar dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>2023-09-18 13:47:28 +0100
committerLibravatar GitHub <noreply@github.com>2023-09-18 13:47:28 +0100
commitc6fdcd52fabb6984de280f763ec5dc2023613054 (patch)
tree939de6cc265fb0c73ef40c2129c8eb298fd93b0c /vendor/google.golang.org/grpc/internal/idle/idle.go
parent[chore]: Bump github.com/miekg/dns from 1.1.55 to 1.1.56 (#2204) (diff)
downloadgotosocial-c6fdcd52fabb6984de280f763ec5dc2023613054.tar.xz
[chore]: Bump go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp from 1.17.0 to 1.18.0 (#2207)
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Diffstat (limited to 'vendor/google.golang.org/grpc/internal/idle/idle.go')
-rw-r--r--vendor/google.golang.org/grpc/internal/idle/idle.go301
1 files changed, 301 insertions, 0 deletions
diff --git a/vendor/google.golang.org/grpc/internal/idle/idle.go b/vendor/google.golang.org/grpc/internal/idle/idle.go
new file mode 100644
index 000000000..6c272476e
--- /dev/null
+++ b/vendor/google.golang.org/grpc/internal/idle/idle.go
@@ -0,0 +1,301 @@
+/*
+ *
+ * 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"
+
+ "google.golang.org/grpc/grpclog"
+)
+
+// 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() error
+}
+
+// Manager defines the functionality required to track RPC activity on a
+// channel.
+type Manager interface {
+ OnCallBegin() error
+ OnCallEnd()
+ Close()
+}
+
+type noopManager struct{}
+
+func (noopManager) OnCallBegin() error { return nil }
+func (noopManager) OnCallEnd() {}
+func (noopManager) Close() {}
+
+// manager implements the Manager interface. It uses atomic operations to
+// synchronize access to shared state and a mutex to guarantee mutual exclusion
+// in a critical section.
+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 int64 // Idle timeout duration nanos stored as an int64.
+ logger grpclog.LoggerV2
+
+ // 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
+}
+
+// ManagerOptions is a collection of options used by
+// NewManager.
+type ManagerOptions struct {
+ Enforcer Enforcer
+ Timeout time.Duration
+ Logger grpclog.LoggerV2
+}
+
+// NewManager creates a new idleness manager implementation for the
+// given idle timeout.
+func NewManager(opts ManagerOptions) Manager {
+ if opts.Timeout == 0 {
+ return noopManager{}
+ }
+
+ m := &manager{
+ enforcer: opts.Enforcer,
+ timeout: int64(opts.Timeout),
+ logger: opts.Logger,
+ }
+ m.timer = timeAfterFunc(opts.Timeout, m.handleIdleTimeout)
+ return m
+}
+
+// resetIdleTimer resets the idle timer to the given duration. This method
+// should only be called from the timer callback.
+func (m *manager) resetIdleTimer(d time.Duration) {
+ m.idleMu.Lock()
+ defer m.idleMu.Unlock()
+
+ if m.timer == nil {
+ // Only close sets timer to nil. We are done.
+ return
+ }
+
+ // It is safe to ignore the return value from Reset() because this method is
+ // only ever called from the timer callback, which means the timer has
+ // already fired.
+ m.timer.Reset(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(time.Duration(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) + m.timeout - time.Now().UnixNano()))
+ return
+ }
+
+ // This CAS operation is extremely likely to succeed given that there has
+ // been no activity since the last time we were here. 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 at the top of this method, or one was ongoing from before
+ // the last time we were here. In both case, reset the timer and return.
+ m.resetIdleTimer(time.Duration(m.timeout))
+ return
+ }
+
+ // Now that we've set the active calls count to -math.MaxInt32, it's time to
+ // actually move to idle mode.
+ 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.
+ atomic.AddInt32(&m.activeCallsCount, math.MaxInt32)
+ m.resetIdleTimer(time.Duration(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 {
+ 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.
+ return false
+ }
+ if atomic.LoadInt32(&m.activeSinceLastTimerCheck) == 1 {
+ // An 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.
+ return false
+ }
+
+ // No new RPCs have come in since we last set the active calls count value
+ // -math.MaxInt32 in the timer callback. And since we have the lock, it is
+ // safe to enter idle mode now.
+ if err := m.enforcer.EnterIdleMode(); err != nil {
+ m.logger.Errorf("Failed to enter idle mode: %v", err)
+ return false
+ }
+
+ // Successfully entered idle mode.
+ m.actuallyIdle = true
+ return true
+}
+
+// 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 the channel to exit idle mode.
+//
+// Holds idleMu which ensures mutual exclusion with tryEnterIdleMode.
+func (m *manager) exitIdleMode() error {
+ m.idleMu.Lock()
+ defer m.idleMu.Unlock()
+
+ if !m.actuallyIdle {
+ // This can happen in two 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.
+ //
+ // Either way, nothing to do here.
+ return nil
+ }
+
+ if err := m.enforcer.ExitIdleMode(); err != nil {
+ return fmt.Errorf("channel failed to exit idle mode: %v", 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.timer = timeAfterFunc(time.Duration(m.timeout), m.handleIdleTimeout)
+ 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()
+ m.timer.Stop()
+ m.timer = nil
+ m.idleMu.Unlock()
+}