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author | 2023-09-18 13:47:28 +0100 | |
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committer | 2023-09-18 13:47:28 +0100 | |
commit | c6fdcd52fabb6984de280f763ec5dc2023613054 (patch) | |
tree | 939de6cc265fb0c73ef40c2129c8eb298fd93b0c /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) | |
download | gotosocial-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.go | 301 |
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() +} |