聊聊tempo的ExclusiveQueues

Posted 2021-10-09 codecraft

序

本文主要研究一下tempo的ExclusiveQueues

ExclusiveQueues

tempo/pkg/flushqueues/exclusivequeues.go

type ExclusiveQueues struct {
    queues     []*util.PriorityQueue
    index      *atomic.Int32
    activeKeys sync.Map
}

ExclusiveQueues定义了queues、index、activeKeys属性

New

tempo/pkg/flushqueues/exclusivequeues.go

// New creates a new set of flush queues with a prom gauge to track current depth
func New(queues int, metric prometheus.Gauge) *ExclusiveQueues {
    f := &ExclusiveQueues{
        queues: make([]*util.PriorityQueue, queues),
        index:  atomic.NewInt32(0),
    }

    for j := 0; j < queues; j++ {
        f.queues[j] = util.NewPriorityQueue(metric)
    }

    return f
}

New方法先创建ExclusiveQueues，然后根据指定的queue个数通过util.NewPriorityQueue(metric)创建PriorityQueue

Enqueue

tempo/pkg/flushqueues/exclusivequeues.go

// Enqueue adds the op to the next queue and prevents any other items to be added with this key
func (f *ExclusiveQueues) Enqueue(op util.Op) {
    _, ok := f.activeKeys.Load(op.Key())
    if ok {
        return
    }

    f.activeKeys.Store(op.Key(), struct{}{})
    f.Requeue(op)
}

Enqueue方法先从activeKeys查找指定的key，若已经存在则提前返回，不存在则放入activeKeys中，然后执行f.Requeue(op)

Requeue

tempo/pkg/flushqueues/exclusivequeues.go

// Requeue adds an op that is presumed to already be covered by activeKeys
func (f *ExclusiveQueues) Requeue(op util.Op) {
    flushQueueIndex := int(f.index.Inc()) % len(f.queues)
    f.queues[flushQueueIndex].Enqueue(op)
}

Requeue方法首先通过int(f.index.Inc()) % len(f.queues)计算flushQueueIndex，然后找到对应的queue，执行Enqueue方法

Dequeue

tempo/pkg/flushqueues/exclusivequeues.go

// Dequeue removes the next op from the requested queue.  After dequeueing the calling
//  process either needs to call ClearKey or Requeue
func (f *ExclusiveQueues) Dequeue(q int) util.Op {
    return f.queues[q].Dequeue()
}

Dequeue方法执行f.queues[q]对应queue的Dequeue

Clear

tempo/pkg/flushqueues/exclusivequeues.go

// Clear unblocks the requested op.  This should be called only after a flush has been successful
func (f *ExclusiveQueues) Clear(op util.Op) {
    f.activeKeys.Delete(op.Key())
}

Clear方法将指定key从activeKeys中移除

Stop

tempo/pkg/flushqueues/exclusivequeues.go

// Stop closes all queues
func (f *ExclusiveQueues) Stop() {
    for _, q := range f.queues {
        q.Close()
    }
}

Stop方法遍历f.queues，挨个执行q.Close()

小结

tempo的ExclusiveQueues定义了queues、index、activeKeys属性；它提供了Enqueue、Requeue、Dequeue、Clear、Stop方法。

doc

• tempo