94 lines
2.2 KiB
Go
94 lines
2.2 KiB
Go
// Package metrics provides common functionality for working with metrics,
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// particularly useful for monitoring components. It includes types to store,
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// check and filter metrics.
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package metrics
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import (
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"container/ring"
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"errors"
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"sync"
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"time"
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"github.com/ipfs-cluster/ipfs-cluster/api"
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)
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// DefaultWindowCap sets the amount of metrics to store per peer.
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var DefaultWindowCap = 25
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// ErrNoMetrics is returned when there are no metrics in a Window.
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var ErrNoMetrics = errors.New("no metrics have been added to this window")
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// Window implements a circular queue to store metrics.
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type Window struct {
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wMu sync.RWMutex
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window *ring.Ring
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}
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// NewWindow creates an instance with the given
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// window capacity.
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func NewWindow(windowCap int) *Window {
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if windowCap <= 0 {
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panic("invalid windowCap")
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}
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w := ring.New(windowCap)
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return &Window{
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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. Add leaves the cursor on the next spot,
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// which is either empty or the oldest record.
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func (mw *Window) Add(m api.Metric) {
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m.ReceivedAt = time.Now().UnixNano()
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mw.wMu.Lock()
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mw.window.Value = m
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mw.window = mw.window.Next()
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mw.wMu.Unlock()
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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 *Window) Latest() (api.Metric, error) {
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var last api.Metric
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var ok bool
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mw.wMu.RLock()
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// This just returns the previous ring and
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// doesn't set the window "cursor" to the previous
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// ring. Therefore this is just a read operation
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// as well.
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prevRing := mw.window.Prev()
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mw.wMu.RUnlock()
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last, ok = prevRing.Value.(api.Metric)
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if !ok || !last.Defined() {
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return last, ErrNoMetrics
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}
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return 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 *Window) All() []api.Metric {
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values := make([]api.Metric, 0, mw.window.Len())
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mw.wMu.RLock()
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mw.window.Do(func(v interface{}) {
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i, ok := v.(api.Metric)
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if ok {
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// append younger values to older value
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values = append([]api.Metric{i}, values...)
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}
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})
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mw.wMu.RUnlock()
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return values
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}
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