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87 lines
2.3 KiB
87 lines
2.3 KiB
// Copyright (c) 2019 The Jaeger Authors.
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// Copyright (c) 2017 Uber Technologies, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package tracing
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import (
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"context"
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"fmt"
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"sync"
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"go.opentelemetry.io/otel/attribute"
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"go.opentelemetry.io/otel/trace"
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"go.uber.org/zap"
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"github.com/jaegertracing/jaeger/examples/hotrod/pkg/log"
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)
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// Mutex is just like the standard sync.Mutex, except that it is aware of the Context
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// and logs some diagnostic information into the current span.
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type Mutex struct {
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SessionBaggageKey string
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LogFactory log.Factory
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realLock sync.Mutex
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holder string
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waiters []string
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waitersLock sync.Mutex
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}
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// Lock acquires an exclusive lock.
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func (sm *Mutex) Lock(ctx context.Context) {
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logger := sm.LogFactory.For(ctx)
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session := BaggageItem(ctx, sm.SessionBaggageKey)
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activeSpan := trace.SpanFromContext(ctx)
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activeSpan.SetAttributes(attribute.String(sm.SessionBaggageKey, session))
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sm.waitersLock.Lock()
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if waiting := len(sm.waiters); waiting > 0 && activeSpan != nil {
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logger.Info(
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fmt.Sprintf("Waiting for lock behind %d transactions", waiting),
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zap.String("blockers", fmt.Sprintf("%v", sm.waiters)),
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)
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}
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sm.waiters = append(sm.waiters, session)
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sm.waitersLock.Unlock()
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sm.realLock.Lock()
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sm.holder = session
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sm.waitersLock.Lock()
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behindLen := len(sm.waiters) - 1
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behindIDs := fmt.Sprintf("%v", sm.waiters[1:]) // skip self
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sm.waitersLock.Unlock()
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logger.Info(
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fmt.Sprintf("Acquired lock; %d transactions waiting behind", behindLen),
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zap.String("waiters", behindIDs),
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)
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}
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// Unlock releases the lock.
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func (sm *Mutex) Unlock() {
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sm.waitersLock.Lock()
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for i, v := range sm.waiters {
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if v == sm.holder {
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sm.waiters = append(sm.waiters[0:i], sm.waiters[i+1:]...)
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break
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}
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}
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sm.waitersLock.Unlock()
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sm.realLock.Unlock()
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}
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