cc-metric-store/internal/memorystore/checkpoint.go

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2024-05-06 14:20:43 +02:00
package memorystore
import (
"bufio"
"context"
"encoding/json"
"errors"
"fmt"
"io/fs"
"log"
"os"
"path"
"path/filepath"
"runtime"
"sort"
"strconv"
"strings"
"sync"
"sync/atomic"
"time"
"github.com/ClusterCockpit/cc-metric-store/internal/config"
"github.com/ClusterCockpit/cc-metric-store/internal/util"
)
// Whenever changed, update MarshalJSON as well!
type CheckpointMetrics struct {
Data []util.Float `json:"data"`
Frequency int64 `json:"frequency"`
Start int64 `json:"start"`
}
type CheckpointFile struct {
Metrics map[string]*CheckpointMetrics `json:"metrics"`
Children map[string]*CheckpointFile `json:"children"`
From int64 `json:"from"`
To int64 `json:"to"`
}
var lastCheckpoint time.Time
func Checkpointing(wg *sync.WaitGroup, ctx context.Context) {
lastCheckpoint = time.Now()
ms := GetMemoryStore()
go func() {
defer wg.Done()
d, err := time.ParseDuration(config.Keys.Checkpoints.Interval)
if err != nil {
log.Fatal(err)
}
if d <= 0 {
return
}
ticks := func() <-chan time.Time {
if d <= 0 {
return nil
}
return time.NewTicker(d).C
}()
for {
select {
case <-ctx.Done():
return
case <-ticks:
log.Printf("start checkpointing (starting at %s)...\n", lastCheckpoint.Format(time.RFC3339))
now := time.Now()
n, err := ms.ToCheckpoint(config.Keys.Checkpoints.RootDir,
lastCheckpoint.Unix(), now.Unix())
if err != nil {
log.Printf("checkpointing failed: %s\n", err.Error())
} else {
log.Printf("done: %d checkpoint files created\n", n)
lastCheckpoint = now
}
}
}
}()
}
// As `Float` implements a custom MarshalJSON() function,
// serializing an array of such types has more overhead
// than one would assume (because of extra allocations, interfaces and so on).
func (cm *CheckpointMetrics) MarshalJSON() ([]byte, error) {
buf := make([]byte, 0, 128+len(cm.Data)*8)
buf = append(buf, `{"frequency":`...)
buf = strconv.AppendInt(buf, cm.Frequency, 10)
buf = append(buf, `,"start":`...)
buf = strconv.AppendInt(buf, cm.Start, 10)
buf = append(buf, `,"data":[`...)
for i, x := range cm.Data {
if i != 0 {
buf = append(buf, ',')
}
if x.IsNaN() {
buf = append(buf, `null`...)
} else {
buf = strconv.AppendFloat(buf, float64(x), 'f', 1, 32)
}
}
buf = append(buf, `]}`...)
return buf, nil
}
// Metrics stored at the lowest 2 levels are not stored away (root and cluster)!
// On a per-host basis a new JSON file is created. I have no idea if this will scale.
// The good thing: Only a host at a time is locked, so this function can run
// in parallel to writes/reads.
func (m *MemoryStore) ToCheckpoint(dir string, from, to int64) (int, error) {
levels := make([]*Level, 0)
selectors := make([][]string, 0)
m.root.lock.RLock()
for sel1, l1 := range m.root.children {
l1.lock.RLock()
for sel2, l2 := range l1.children {
levels = append(levels, l2)
selectors = append(selectors, []string{sel1, sel2})
}
l1.lock.RUnlock()
}
m.root.lock.RUnlock()
type workItem struct {
level *Level
dir string
selector []string
}
n, errs := int32(0), int32(0)
var wg sync.WaitGroup
wg.Add(NumWorkers)
work := make(chan workItem, NumWorkers*2)
for worker := 0; worker < NumWorkers; worker++ {
go func() {
defer wg.Done()
for workItem := range work {
if err := workItem.level.toCheckpoint(workItem.dir, from, to, m); err != nil {
if err == ErrNoNewData {
continue
}
log.Printf("error while checkpointing %#v: %s", workItem.selector, err.Error())
atomic.AddInt32(&errs, 1)
} else {
atomic.AddInt32(&n, 1)
}
}
}()
}
for i := 0; i < len(levels); i++ {
dir := path.Join(dir, path.Join(selectors[i]...))
work <- workItem{
level: levels[i],
dir: dir,
selector: selectors[i],
}
}
close(work)
wg.Wait()
if errs > 0 {
return int(n), fmt.Errorf("%d errors happend while creating checkpoints (%d successes)", errs, n)
}
return int(n), nil
}
func (l *Level) toCheckpointFile(from, to int64, m *MemoryStore) (*CheckpointFile, error) {
l.lock.RLock()
defer l.lock.RUnlock()
retval := &CheckpointFile{
From: from,
To: to,
Metrics: make(map[string]*CheckpointMetrics),
Children: make(map[string]*CheckpointFile),
}
for metric, minfo := range m.Metrics {
b := l.metrics[minfo.Offset]
if b == nil {
continue
}
allArchived := true
b.iterFromTo(from, to, func(b *buffer) error {
if !b.archived {
allArchived = false
}
return nil
})
if allArchived {
continue
}
data := make([]util.Float, (to-from)/b.frequency+1)
data, start, end, err := b.read(from, to, data)
if err != nil {
return nil, err
}
for i := int((end - start) / b.frequency); i < len(data); i++ {
data[i] = util.NaN
}
retval.Metrics[metric] = &CheckpointMetrics{
Frequency: b.frequency,
Start: start,
Data: data,
}
}
for name, child := range l.children {
val, err := child.toCheckpointFile(from, to, m)
if err != nil {
return nil, err
}
if val != nil {
retval.Children[name] = val
}
}
if len(retval.Children) == 0 && len(retval.Metrics) == 0 {
return nil, nil
}
return retval, nil
}
func (l *Level) toCheckpoint(dir string, from, to int64, m *MemoryStore) error {
cf, err := l.toCheckpointFile(from, to, m)
if err != nil {
return err
}
if cf == nil {
return ErrNoNewData
}
filepath := path.Join(dir, fmt.Sprintf("%d.json", from))
f, err := os.OpenFile(filepath, os.O_CREATE|os.O_WRONLY, 0o644)
if err != nil && os.IsNotExist(err) {
err = os.MkdirAll(dir, 0o755)
if err == nil {
f, err = os.OpenFile(filepath, os.O_CREATE|os.O_WRONLY, 0o644)
}
}
if err != nil {
return err
}
defer f.Close()
bw := bufio.NewWriter(f)
if err = json.NewEncoder(bw).Encode(cf); err != nil {
return err
}
return bw.Flush()
}
// Metrics stored at the lowest 2 levels are not loaded (root and cluster)!
// This function can only be called once and before the very first write or read.
// Different host's data is loaded to memory in parallel.
func (m *MemoryStore) FromCheckpoint(dir string, from int64) (int, error) {
var wg sync.WaitGroup
work := make(chan [2]string, NumWorkers)
n, errs := int32(0), int32(0)
wg.Add(NumWorkers)
for worker := 0; worker < NumWorkers; worker++ {
go func() {
defer wg.Done()
for host := range work {
lvl := m.root.findLevelOrCreate(host[:], len(m.Metrics))
nn, err := lvl.fromCheckpoint(filepath.Join(dir, host[0], host[1]), from, m)
if err != nil {
log.Fatalf("error while loading checkpoints: %s", err.Error())
atomic.AddInt32(&errs, 1)
}
atomic.AddInt32(&n, int32(nn))
}
}()
}
i := 0
clustersDir, err := os.ReadDir(dir)
for _, clusterDir := range clustersDir {
if !clusterDir.IsDir() {
err = errors.New("expected only directories at first level of checkpoints/ directory")
goto done
}
hostsDir, e := os.ReadDir(filepath.Join(dir, clusterDir.Name()))
if e != nil {
err = e
goto done
}
for _, hostDir := range hostsDir {
if !hostDir.IsDir() {
err = errors.New("expected only directories at second level of checkpoints/ directory")
goto done
}
i++
if i%NumWorkers == 0 && i > 100 {
// Forcing garbage collection runs here regulary during the loading of checkpoints
// will decrease the total heap size after loading everything back to memory is done.
// While loading data, the heap will grow fast, so the GC target size will double
// almost always. By forcing GCs here, we can keep it growing more slowly so that
// at the end, less memory is wasted.
runtime.GC()
}
work <- [2]string{clusterDir.Name(), hostDir.Name()}
}
}
done:
close(work)
wg.Wait()
if err != nil {
return int(n), err
}
if errs > 0 {
return int(n), fmt.Errorf("%d errors happend while creating checkpoints (%d successes)", errs, n)
}
return int(n), nil
}
func (l *Level) loadFile(cf *CheckpointFile, m *MemoryStore) error {
for name, metric := range cf.Metrics {
n := len(metric.Data)
b := &buffer{
frequency: metric.Frequency,
start: metric.Start,
data: metric.Data[0:n:n], // Space is wasted here :(
prev: nil,
next: nil,
archived: true,
}
b.close()
minfo, ok := m.Metrics[name]
if !ok {
continue
// return errors.New("Unkown metric: " + name)
}
prev := l.metrics[minfo.Offset]
if prev == nil {
l.metrics[minfo.Offset] = b
} else {
if prev.start > b.start {
return errors.New("wooops")
}
b.prev = prev
prev.next = b
}
l.metrics[minfo.Offset] = b
}
if len(cf.Children) > 0 && l.children == nil {
l.children = make(map[string]*Level)
}
for sel, childCf := range cf.Children {
child, ok := l.children[sel]
if !ok {
child = &Level{
metrics: make([]*buffer, len(m.Metrics)),
children: nil,
}
l.children[sel] = child
}
if err := child.loadFile(childCf, m); err != nil {
return err
}
}
return nil
}
func (l *Level) fromCheckpoint(dir string, from int64, m *MemoryStore) (int, error) {
direntries, err := os.ReadDir(dir)
if err != nil {
if os.IsNotExist(err) {
return 0, nil
}
return 0, err
}
jsonFiles := make([]fs.DirEntry, 0)
filesLoaded := 0
for _, e := range direntries {
if e.IsDir() {
child := &Level{
metrics: make([]*buffer, len(m.Metrics)),
children: make(map[string]*Level),
}
files, err := child.fromCheckpoint(path.Join(dir, e.Name()), from, m)
filesLoaded += files
if err != nil {
return filesLoaded, err
}
l.children[e.Name()] = child
} else if strings.HasSuffix(e.Name(), ".json") {
jsonFiles = append(jsonFiles, e)
} else {
return filesLoaded, errors.New("unexpected file: " + dir + "/" + e.Name())
}
}
files, err := findFiles(jsonFiles, from, true)
if err != nil {
return filesLoaded, err
}
for _, filename := range files {
f, err := os.Open(path.Join(dir, filename))
if err != nil {
return filesLoaded, err
}
defer f.Close()
br := bufio.NewReader(f)
cf := &CheckpointFile{}
if err = json.NewDecoder(br).Decode(cf); err != nil {
return filesLoaded, err
}
if cf.To != 0 && cf.To < from {
continue
}
if err = l.loadFile(cf, m); err != nil {
return filesLoaded, err
}
filesLoaded += 1
}
return filesLoaded, nil
}
// This will probably get very slow over time!
// A solution could be some sort of an index file in which all other files
// and the timespan they contain is listed.
func findFiles(direntries []fs.DirEntry, t int64, findMoreRecentFiles bool) ([]string, error) {
nums := map[string]int64{}
for _, e := range direntries {
ts, err := strconv.ParseInt(strings.TrimSuffix(e.Name(), ".json"), 10, 64)
if err != nil {
return nil, err
}
nums[e.Name()] = ts
}
sort.Slice(direntries, func(i, j int) bool {
a, b := direntries[i], direntries[j]
return nums[a.Name()] < nums[b.Name()]
})
filenames := make([]string, 0)
for i := 0; i < len(direntries); i++ {
e := direntries[i]
ts1 := nums[e.Name()]
if findMoreRecentFiles && t <= ts1 || i == len(direntries)-1 {
filenames = append(filenames, e.Name())
continue
}
enext := direntries[i+1]
ts2 := nums[enext.Name()]
if findMoreRecentFiles {
if ts1 < t && t < ts2 {
filenames = append(filenames, e.Name())
}
} else {
if ts2 < t {
filenames = append(filenames, e.Name())
}
}
}
return filenames, nil
}