88 lines
2.0 KiB
Go
88 lines
2.0 KiB
Go
// Package util provides common functionality for monitoring components.
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package util
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import (
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"errors"
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"sync"
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"github.com/ipfs/ipfs-cluster/api"
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)
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var ErrNoMetrics = errors.New("no metrics have been added to this window")
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// MetricsWindow implements a circular queue to store metrics.
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type MetricsWindow struct {
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last int
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safe bool
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windowLock sync.RWMutex
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window []api.Metric
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}
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// NewMetricsWindow creates an instance with the given
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// window capacity. The safe indicates whether we use a lock
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// for concurrent operations.
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func NewMetricsWindow(windowCap int, safe bool) *MetricsWindow {
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w := make([]api.Metric, 0, windowCap)
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return &MetricsWindow{
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last: 0,
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safe: safe,
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window: w,
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}
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}
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// Add adds a new metric to the window. If the window capacity
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// has been reached, the oldest metric (by the time it was added),
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// will be discarded.
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func (mw *MetricsWindow) Add(m api.Metric) {
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if mw.safe {
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mw.windowLock.Lock()
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defer mw.windowLock.Unlock()
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}
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if len(mw.window) < cap(mw.window) {
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mw.window = append(mw.window, m)
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mw.last = len(mw.window) - 1
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return
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}
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// len == cap
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mw.last = (mw.last + 1) % cap(mw.window)
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mw.window[mw.last] = m
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return
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}
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// Latest returns the last metric added. It returns an error
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// if no metrics were added.
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func (mw *MetricsWindow) Latest() (api.Metric, error) {
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if mw.safe {
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mw.windowLock.Lock()
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defer mw.windowLock.Unlock()
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}
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if len(mw.window) == 0 {
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return api.Metric{}, ErrNoMetrics
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}
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return mw.window[mw.last], nil
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}
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// All returns all the metrics in the window, in the inverse order
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// they were Added. That is, result[0] will be the last added
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// metric.
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func (mw *MetricsWindow) All() []api.Metric {
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if mw.safe {
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mw.windowLock.Lock()
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defer mw.windowLock.Unlock()
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}
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wlen := len(mw.window)
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res := make([]api.Metric, 0, wlen)
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if wlen == 0 {
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return res
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}
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for i := mw.last; i >= 0; i-- {
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res = append(res, mw.window[i])
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}
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for i := wlen - 1; i > mw.last; i-- {
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res = append(res, mw.window[i])
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}
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return res
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}
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