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Fix panic in usagestats #706

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May 23, 2023
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Fix panic in usagestats #706

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203 changes: 137 additions & 66 deletions pkg/usagestats/stats.go
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,8 @@ var (
statsPrefix = "github.com/grafana/phlare/"
targetKey = "target"
editionKey = "edition"

createLock sync.RWMutex
)

// Report is the JSON object sent to the stats server
Expand Down Expand Up @@ -156,40 +158,61 @@ func memstats() interface{} {
// NewFloat returns a new Float stats object.
// If a Float stats object with the same name already exists it is returned.
func NewFloat(name string) *expvar.Float {
existing := expvar.Get(statsPrefix + name)
if existing != nil {
if f, ok := existing.(*expvar.Float); ok {
return f
}
panic(fmt.Sprintf("%v is set to a non-float value", name))
}
return expvar.NewFloat(statsPrefix + name)
return createOrRetrieveExpvar(
func() (*expvar.Float, error) { // check
existing := expvar.Get(statsPrefix + name)
if existing != nil {
if f, ok := existing.(*expvar.Float); ok {
return f, nil
}
return nil, fmt.Errorf("%v is set to a non-float value", name)
}
return nil, nil
},
func() *expvar.Float { // create
return expvar.NewFloat(statsPrefix + name)
},
)
}

// NewInt returns a new Int stats object.
// If an Int stats object object with the same name already exists it is returned.
func NewInt(name string) *expvar.Int {
existing := expvar.Get(statsPrefix + name)
if existing != nil {
if i, ok := existing.(*expvar.Int); ok {
return i
}
panic(fmt.Sprintf("%v is set to a non-int value", name))
}
return expvar.NewInt(statsPrefix + name)
return createOrRetrieveExpvar(
func() (*expvar.Int, error) { // check
existing := expvar.Get(statsPrefix + name)
if existing != nil {
if i, ok := existing.(*expvar.Int); ok {
return i, nil
}
return nil, fmt.Errorf("%v is set to a non-int value", name)
}
return nil, nil
},
func() *expvar.Int { // create
return expvar.NewInt(statsPrefix + name)
},
)
}

// NewString returns a new String stats object.
// If a String stats object with the same name already exists it is returned.
func NewString(name string) *expvar.String {
existing := expvar.Get(statsPrefix + name)
if existing != nil {
if s, ok := existing.(*expvar.String); ok {
return s
}
panic(fmt.Sprintf("%v is set to a non-string value", name))
}
return expvar.NewString(statsPrefix + name)
return createOrRetrieveExpvar(
func() (*expvar.String, error) { // check
existing := expvar.Get(statsPrefix + name)
if existing != nil {
if s, ok := existing.(*expvar.String); ok {
return s, nil
}
return nil, fmt.Errorf("%v is set to a non-string value", name)
}
return nil, nil
},
func() *expvar.String { // create
return expvar.NewString(statsPrefix + name)
},
)
}

// Target sets the target name. This can be set multiple times.
Expand Down Expand Up @@ -225,23 +248,31 @@ type Statistics struct {
// - stdvar
// If a Statistics object with the same name already exists it is returned.
func NewStatistics(name string) *Statistics {
s := &Statistics{
min: atomic.NewFloat64(math.Inf(0)),
max: atomic.NewFloat64(math.Inf(-1)),
count: atomic.NewInt64(0),
avg: atomic.NewFloat64(0),
mean: atomic.NewFloat64(0),
value: atomic.NewFloat64(0),
}
existing := expvar.Get(statsPrefix + name)
if existing != nil {
if s, ok := existing.(*Statistics); ok {
return createOrRetrieveExpvar(
func() (*Statistics, error) { // check

existing := expvar.Get(statsPrefix + name)
if existing != nil {
if s, ok := existing.(*Statistics); ok {
return s, nil
}
return nil, fmt.Errorf("%v is set to a non-Statistics value", name)
}
return nil, nil
},
func() *Statistics { // create
s := &Statistics{
min: atomic.NewFloat64(math.Inf(0)),
max: atomic.NewFloat64(math.Inf(-1)),
count: atomic.NewInt64(0),
avg: atomic.NewFloat64(0),
mean: atomic.NewFloat64(0),
value: atomic.NewFloat64(0),
}
expvar.Publish(statsPrefix+name, s)
return s
}
panic(fmt.Sprintf("%v is set to a non-Statistics value", name))
}
expvar.Publish(statsPrefix+name, s)
return s
},
)
}

func (s *Statistics) String() string {
Expand Down Expand Up @@ -316,23 +347,56 @@ type Counter struct {
resetTime time.Time
}

func createOrRetrieveExpvar[K any](check func() (*K, error), create func() *K) *K {
// check if string exists holding read lock
createLock.RLock()
s, err := check()
createLock.RUnlock()
if err != nil {
panic(err.Error())
}
if s != nil {
return s
}

// acquire write lock and check again and create if still missing
createLock.Lock()
defer createLock.Unlock()
s, err = check()
if err != nil {
panic(err.Error())
}
if s != nil {
return s
}

return create()
}

// NewCounter returns a new Counter stats object.
// If a Counter stats object with the same name already exists it is returned.
func NewCounter(name string) *Counter {
existing := expvar.Get(statsPrefix + name)
if existing != nil {
if c, ok := existing.(*Counter); ok {
return createOrRetrieveExpvar(
func() (*Counter, error) { // check
existing := expvar.Get(statsPrefix + name)
if existing != nil {
if c, ok := existing.(*Counter); ok {
return c, nil
}
return nil, fmt.Errorf("%v is set to a non-Counter value", name)
}
return nil, nil
},
func() *Counter { // create
c := &Counter{
total: atomic.NewInt64(0),
rate: atomic.NewFloat64(0),
resetTime: time.Now(),
}
expvar.Publish(statsPrefix+name, c)
return c
}
panic(fmt.Sprintf("%v is set to a non-Counter value", name))
}
c := &Counter{
total: atomic.NewInt64(0),
rate: atomic.NewFloat64(0),
resetTime: time.Now(),
}
expvar.Publish(statsPrefix+name, c)
return c
},
)
}

func (c *Counter) updateRate() {
Expand Down Expand Up @@ -371,19 +435,26 @@ type WordCounter struct {
// The WordCounter object is thread-safe and counts the number of words recorded.
// If a WordCounter stats object with the same name already exists it is returned.
func NewWordCounter(name string) *WordCounter {
c := &WordCounter{
count: atomic.NewInt64(0),
words: sync.Map{},
}
existing := expvar.Get(statsPrefix + name)
if existing != nil {
if w, ok := existing.(*WordCounter); ok {
return w
}
panic(fmt.Sprintf("%v is set to a non-WordCounter value", name))
}
expvar.Publish(statsPrefix+name, c)
return c
return createOrRetrieveExpvar(
func() (*WordCounter, error) { // check
existing := expvar.Get(statsPrefix + name)
if existing != nil {
if w, ok := existing.(*WordCounter); ok {
return w, nil
}
return nil, fmt.Errorf("%v is set to a non-WordCounter value", name)
}
return nil, nil
},
func() *WordCounter { // create
c := &WordCounter{
count: atomic.NewInt64(0),
words: sync.Map{},
}
expvar.Publish(statsPrefix+name, c)
return c
},
)
}

func (w *WordCounter) Add(word string) {
Expand Down