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stats_buffer.go
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/
stats_buffer.go
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// Copyright 2014 Google Inc. All Rights Reserved.
//
// 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 memory
import (
"sort"
"time"
info "github.com/google/cadvisor/info/v1"
)
// A circular buffer for ContainerStats.
type StatsBuffer struct {
buffer []info.ContainerStats
size int
index int
}
// Returns a new thread-compatible StatsBuffer.
func NewStatsBuffer(size int) *StatsBuffer {
return &StatsBuffer{
buffer: make([]info.ContainerStats, size),
size: 0,
index: size - 1,
}
}
// Adds an element to the start of the buffer (removing one from the end if necessary).
func (self *StatsBuffer) Add(item *info.ContainerStats) {
if self.size < len(self.buffer) {
self.size++
}
self.index = (self.index + 1) % len(self.buffer)
self.buffer[self.index] = *item
}
// Returns up to maxResult elements in the specified time period (inclusive).
// Results are from first to last. maxResults of -1 means no limit. When first
// and last are specified, maxResults is ignored.
func (self *StatsBuffer) InTimeRange(start, end time.Time, maxResults int) []*info.ContainerStats {
// No stats, return empty.
if self.size == 0 {
return []*info.ContainerStats{}
}
// Return all results in a time range if specified.
if !start.IsZero() && !end.IsZero() {
maxResults = -1
}
// NOTE: Since we store the elments in descending timestamp order "start" will
// be a higher index than "end".
var startIndex int
if start.IsZero() {
// None specified, start at the beginning.
startIndex = self.size - 1
} else {
// Start is the index before the elements smaller than it. We do this by
// finding the first element smaller than start and taking the index
// before that element
startIndex = sort.Search(self.size, func(index int) bool {
// buffer[index] < start
return self.Get(index).Timestamp.Before(start)
}) - 1
// Check if start is after all the data we have.
if startIndex < 0 {
return []*info.ContainerStats{}
}
}
var endIndex int
if end.IsZero() {
// None specified, end with the latest stats.
endIndex = 0
} else {
// End is the first index smaller than or equal to it (so, not larger).
endIndex = sort.Search(self.size, func(index int) bool {
// buffer[index] <= t -> !(buffer[index] > t)
return !self.Get(index).Timestamp.After(end)
})
// Check if end is before all the data we have.
if endIndex == self.size {
return []*info.ContainerStats{}
}
}
// Trim to maxResults size.
numResults := startIndex - endIndex + 1
if maxResults != -1 && numResults > maxResults {
startIndex -= numResults - maxResults
numResults = maxResults
}
// Return in sorted timestamp order so from the "back" to "front".
result := make([]*info.ContainerStats, numResults)
for i := 0; i < numResults; i++ {
result[i] = self.Get(startIndex - i)
}
return result
}
// TODO(vmarmol): Remove this function as it will no longer be neededt.
// Returns the first N elements in the buffer. If N > size of buffer, size of buffer elements are returned.
// Returns the elements in ascending timestamp order.
func (self *StatsBuffer) FirstN(n int) []*info.ContainerStats {
// Cap n at the number of elements we have.
if n > self.size {
n = self.size
}
// index points to the latest element, get n before that one (keeping in mind we may have gone through 0).
start := self.index - (n - 1)
if start < 0 {
start += len(self.buffer)
}
// Copy the elements.
res := make([]*info.ContainerStats, n)
for i := 0; i < n; i++ {
index := (start + i) % len(self.buffer)
res[i] = &self.buffer[index]
}
return res
}
// Gets the element at the specified index. Note that elements are stored in LIFO order.
func (self *StatsBuffer) Get(index int) *info.ContainerStats {
calculatedIndex := self.index - index
if calculatedIndex < 0 {
calculatedIndex += len(self.buffer)
}
return &self.buffer[calculatedIndex]
}
func (self *StatsBuffer) Size() int {
return self.size
}