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New unfinished MemoryStore implementation

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This commit is contained in:
Lou Knauer 2021-08-31 10:52:22 +02:00
parent a1c41e5f5d
commit 10f0da6000
3 changed files with 275 additions and 250 deletions
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250
memoryStore.go
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@ -1,250 +0,0 @@
package main
import (
"fmt"
"math"
"strings"
"sync"
"time"
"github.com/ClusterCockpit/cc-metric-store/lineprotocol"
)
type storeBuffer struct {
store []lineprotocol.Float
start int64
}
type buffer struct {
current *storeBuffer
next *storeBuffer
lock sync.Mutex
}
//MemoryStore holds the state for a metric memory store.
//It does not export any variable.
type MemoryStore struct {
containers map[string]*buffer
offsets map[string]int
frequency int
numSlots int
numMetrics int
lock sync.Mutex
}
func initBuffer(b *storeBuffer) {
for i := 0; i < len(b.store); i++ {
b.store[i] = lineprotocol.Float(math.NaN())
}
}
func allocateBuffer(ts int64, size int) *buffer {
b := new(buffer)
s := make([]lineprotocol.Float, size)
b.current = &storeBuffer{s, ts}
initBuffer(b.current)
s = make([]lineprotocol.Float, size)
b.next = &storeBuffer{s, 0}
initBuffer(b.next)
return b
}
func switchBuffers(m *MemoryStore, b *buffer) {
initBuffer(b.next)
b.current, b.next = b.next, b.current
b.current.start = b.next.start + int64(m.numSlots*m.frequency)
}
func newMemoryStore(o []string, n int, f int) *MemoryStore {
var m MemoryStore
m.frequency = f
m.numSlots = n
m.containers = make(map[string]*buffer)
m.offsets = make(map[string]int)
for i, name := range o {
m.offsets[name] = i
}
m.numMetrics = len(o)
return &m
}
// AddMetrics writes metrics to the memoryStore for entity key
// at unix epoch time ts. The unit of ts is seconds.
// An error is returned if ts is out of bounds of MemoryStore.
func (m *MemoryStore) AddMetrics(
key string,
ts int64,
metrics []lineprotocol.Metric) error {
m.lock.Lock()
b, ok := m.containers[key]
if !ok {
//Key does not exist. Allocate new buffer.
m.containers[key] = allocateBuffer(ts, m.numMetrics*m.numSlots)
b = m.containers[key]
}
m.lock.Unlock()
b.lock.Lock()
defer b.lock.Unlock()
index := int(ts-b.current.start) / m.frequency
if index < 0 || index >= 2*m.numSlots {
return fmt.Errorf("ts %d out of bounds", ts)
}
if index >= m.numSlots {
//Index exceeds buffer length. Switch buffers.
switchBuffers(m, b)
index = int(ts-b.current.start) / m.frequency
}
s := b.current.store
for _, metric := range metrics {
s[m.offsets[metric.Name]*m.numSlots+index] = metric.Value
}
return nil
}
// GetMetric returns a slize with metric values for timerange
// and entity key. Returns an error if key does not exist,
// stop is before start or start is in the future.
func (m *MemoryStore) GetMetric(
key string,
metric string,
from int64,
to int64) ([]lineprotocol.Float, int64, error) {
m.lock.Lock()
b, ok := m.containers[key]
m.lock.Unlock()
if !ok {
return nil, 0, fmt.Errorf("key %s does not exist", key)
}
b.lock.Lock()
defer b.lock.Unlock()
if to <= from {
return nil, 0, fmt.Errorf("invalid duration %d - %d", from, to)
}
if from > b.current.start+int64(m.numSlots*m.frequency) {
return nil, 0, fmt.Errorf("from %d out of bounds", from)
}
if to < b.next.start {
return nil, 0, fmt.Errorf("to %d out of bounds", to)
}
var values1, values2 []lineprotocol.Float
offset := m.offsets[metric] * m.numSlots
valuesFrom := from
if from < b.current.start && b.next.start != 0 {
var start, stop = 0, m.numSlots
if from > b.next.start {
start = int(from-b.next.start) / m.frequency
} else {
valuesFrom = b.next.start
}
if to < b.current.start {
stop = int(to-b.next.start) / m.frequency
}
// fmt.Println("NEXT", start, stop)
values1 = b.next.store[offset+start : offset+stop]
}
if to >= b.current.start {
var start, stop = 0, m.numSlots
if from > b.current.start {
start = int(from-b.current.start) / m.frequency
}
if to <= b.current.start+int64(m.numSlots*m.frequency) {
stop = int(to-b.current.start) / m.frequency
}
// fmt.Println("CURRENT", start, stop, b.current.start)
values2 = b.current.store[offset+start : offset+stop]
}
return append(values1, values2...), valuesFrom, nil
}
// Call *f* once on every value which *GetMetric* would
// return for similar arguments. This operation might be known
// as fold in Ruby/Haskell/Scala. It can be used to implement
// the calculation of sums, averages, minimas and maximas.
// The advantage of using this over *GetMetric* for such calculations
// is that it can be implemented without copying data.
// TODO: Write Tests, implement without calling GetMetric!
func (m *MemoryStore) Reduce(
key string, metric string,
from int64, to int64,
f func(t int64, acc lineprotocol.Float, x lineprotocol.Float) lineprotocol.Float, initialX lineprotocol.Float) (lineprotocol.Float, error) {
values, valuesFrom, err := m.GetMetric(key, metric, from, to)
if err != nil {
return 0.0, err
}
acc := initialX
t := valuesFrom
for i := 0; i < len(values); i++ {
acc = f(t, acc, values[i])
t += int64(m.frequency)
}
return acc, nil
}
// Return a map of keys to a map of metrics to the most recent value writen to
// the store for that metric.
// TODO: Write Tests!
func (m *MemoryStore) Peak(prefix string) map[string]map[string]lineprotocol.Float {
m.lock.Lock()
defer m.lock.Unlock()
now := time.Now().Unix()
retval := make(map[string]map[string]lineprotocol.Float)
for key, b := range m.containers {
if !strings.HasPrefix(key, prefix) {
continue
}
b.lock.Lock()
index := int(now-b.current.start) / m.frequency
if index >= m.numSlots {
index = m.numSlots - 1
}
vals := make(map[string]lineprotocol.Float)
for metric, offset := range m.offsets {
val := lineprotocol.Float(math.NaN())
for i := index; i >= 0 && math.IsNaN(float64(val)); i -= 1 {
val = b.current.store[offset*m.numSlots+i]
}
vals[metric] = val
}
b.lock.Unlock()
retval[key[len(prefix):]] = vals
}
return retval
}

0
memoryStore_test.go → memoryStore_test.go.orig
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275
memstore.go Normal file
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@ -0,0 +1,275 @@
package main
import (
"errors"
"sync"
)
// Default buffer capacity.
// `buffer.data` will only ever grow up to it's capacity and a new link
// in the buffer chain will be created if needed so that no copying
// of needs to happen on writes.
const (
BUFFER_CAP int = 1024
)
// So that we can reuse allocations
var bufferPool sync.Pool = sync.Pool{
New: func() interface{} {
return make([]Float, 0, BUFFER_CAP)
},
}
// Each metric on each level has it's own buffer.
// This is where the actual values go.
type buffer struct {
frequency int64 // Time between two "slots"
start int64 // Timestamp of when `data[0]` was written.
data []Float // The slice should never reallocacte as `cap(data)` is respected.
prev, next *buffer // `prev` contains older data, `next` newer data.
}
func newBuffer(ts, freq int64) *buffer {
return &buffer{
frequency: freq,
start: ts,
data: bufferPool.Get().([]Float)[:0],
prev: nil,
next: nil,
}
}
// If a new buffer was created, the new head is returnd.
// Otherwise, the existing buffer is returnd.
func (b *buffer) write(ts int64, value Float) (*buffer, error) {
if ts < b.start {
return nil, errors.New("cannot write value to buffer from past")
}
idx := int((ts - b.start) / b.frequency)
if idx >= cap(b.data) {
newbuf := newBuffer(ts, b.frequency)
newbuf.prev = b
b.next = newbuf
b = newbuf
idx = 0
}
// Overwriting value or writing value from past
if idx < len(b.data) {
b.data[idx] = value
return b, nil
}
// Fill up unwritten slots with NaN
for i := len(b.data); i < idx; i++ {
b.data = append(b.data, NaN)
}
b.data = append(b.data, value)
return b, nil
}
// Return all known values from `from` to `to`. Gaps of information are
// represented by NaN. If values at the start or end are missing,
// instead of NaN values, the second and thrid return values contain
// the actual `from`/`to`.
func (b *buffer) read(from, to int64) ([]Float, int64, int64, error) {
if from < b.start {
if b.prev != nil {
return b.prev.read(from, to)
}
from = b.start
}
data := make([]Float, 0, (to-from)/b.frequency+1)
var t int64
for t = from; t < to; t += b.frequency {
idx := int((t - b.start) / b.frequency)
if idx >= cap(b.data) {
b = b.next
if b == nil {
return data, from, t, nil
}
idx = 0
}
if t < b.start || idx >= len(b.data) {
data = append(data, NaN)
} else {
data = append(data, b.data[idx])
}
}
return data, from, t, nil
}
// Could also be called "node" as this forms a node in a tree structure.
// Called level because "node" might be confusing here.
// Can be both a leaf or a inner node. In this structue, inner nodes can
// also hold data (in `metrics`).
type level struct {
lock sync.Mutex // There is performance to be gained by having different locks for `metrics` and `children` (Spinlock?).
metrics map[string]*buffer // Every level can store metrics.
children map[string]*level // Sub-granularities/nodes. Use `sync.Map`?
}
// Caution: the lock of the returned level will be LOCKED.
// Find the correct level for the given selector, creating it if
// it does not exist. Example selector in the context of the
// ClusterCockpit could be: []string{ "emmy", "host123", "cpu", "0" }
// This function would probably benefit a lot from `level.children` beeing a `sync.Map`?
func (l *level) findLevelOrCreate(selector []string) *level {
l.lock.Lock()
if len(selector) == 0 {
return l
}
child, ok := l.children[selector[0]]
if !ok {
child = &level{
metrics: make(map[string]*buffer),
children: make(map[string]*level),
}
l.children[selector[0]] = child
}
l.lock.Unlock()
return child.findLevelOrCreate(selector[1:])
}
// This function assmumes that `l.lock` is LOCKED!
// Read `buffer.read` for context. This function does
// a lot of short-lived allocations and copies if this is
// not the "native" level for the requested metric. There
// is a lot of optimization potential here!
// Optimization suggestion: Pass a buffer as argument onto which the values should be added.
func (l *level) read(metric string, from, to int64, accumulation string) ([]Float, int64, int64, error) {
if b, ok := l.metrics[metric]; ok {
// Whoo, this is the "native" level of this metric:
return b.read(from, to)
}
if len(l.children) == 0 {
return nil, 0, 0, errors.New("no data for that metric/level")
}
if len(l.children) == 1 {
for _, child := range l.children {
child.lock.Lock()
data, from, to, err := child.read(metric, from, to, accumulation)
child.lock.Unlock()
return data, from, to, err
}
}
// "slow" case: We need to accumulate metrics accross levels/scopes/tags/whatever.
var data []Float = nil
for _, child := range l.children {
child.lock.Lock()
cdata, cfrom, cto, err := child.read(metric, from, to, accumulation)
child.lock.Unlock()
if err != nil {
return nil, 0, 0, err
}
if data == nil {
data = cdata
from = cfrom
to = cto
continue
}
if cfrom != from || cto != to {
// TODO: Here, we could take the max of cfrom and from and the min of cto and to instead.
// This would mean that we also have to resize data.
return nil, 0, 0, errors.New("data for metrics at child levels does not align")
}
if len(data) != len(cdata) {
panic("WTF? Different freq. at different levels?")
}
for i := 0; i < len(data); i++ {
data[i] += cdata[i]
}
}
switch accumulation {
case "sum":
return data, from, to, nil
case "avg":
normalize := 1. / Float(len(l.children))
for i := 0; i < len(data); i++ {
data[i] *= normalize
}
return data, from, to, nil
default:
return nil, 0, 0, errors.New("invalid accumulation strategy: " + accumulation)
}
}
type MemoryStore struct {
root level // root of the tree structure
metrics map[string]MetricConfig
}
func NewMemoryStore(metrics map[string]MetricConfig) *MemoryStore {
return &MemoryStore{
root: level{
metrics: make(map[string]*buffer),
children: make(map[string]*level),
},
metrics: metrics,
}
}
// Write all values in `metrics` to the level specified by `selector` for time `ts`.
// Look at `findLevelOrCreate` for how selectors work.
func (m *MemoryStore) Write(selector []string, ts int64, metrics []Metric) error {
l := m.root.findLevelOrCreate(selector)
defer l.lock.Unlock()
for _, metric := range metrics {
b, ok := l.metrics[metric.Name]
if !ok {
minfo, ok := m.metrics[metric.Name]
if !ok {
return errors.New("unkown metric: " + metric.Name)
}
// First write to this metric and level
b = newBuffer(ts, minfo.Frequency)
l.metrics[metric.Name] = b
}
nb, err := b.write(ts, metric.Value)
if err != nil {
return err
}
// Last write created a new buffer...
if b != nb {
l.metrics[metric.Name] = nb
}
}
return nil
}
func (m *MemoryStore) Read(selector []string, metric string, from, to int64) ([]Float, int64, int64, error) {
l := m.root.findLevelOrCreate(selector)
defer l.lock.Unlock()
if from > to {
return nil, 0, 0, errors.New("invalid time range")
}
minfo, ok := m.metrics[metric]
if !ok {
return nil, 0, 0, errors.New("unkown metric: " + metric)
}
return l.read(metric, from, to, minfo.Aggregation)
}