faas/gateway/scaling/function_scaler.go
Alex Ellis (OpenFaaS Ltd) 01841f605c Use sync package from unofficial Go library
Uses the sync package from the unofficial Go library instead
of simpler solution.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alex@openfaas.com>
2022-06-29 09:43:58 +01:00

194 lines
4.4 KiB
Go

package scaling
import (
"fmt"
"log"
"time"
"golang.org/x/sync/singleflight"
)
// NewFunctionScaler create a new scaler with the specified
// ScalingConfig
func NewFunctionScaler(config ScalingConfig, functionCacher FunctionCacher) FunctionScaler {
return FunctionScaler{
Cache: functionCacher,
Config: config,
SingleFlight: &singleflight.Group{},
}
}
// FunctionScaler scales from zero
type FunctionScaler struct {
Cache FunctionCacher
Config ScalingConfig
SingleFlight *singleflight.Group
}
// FunctionScaleResult holds the result of scaling from zero
type FunctionScaleResult struct {
Available bool
Error error
Found bool
Duration time.Duration
}
// Scale scales a function from zero replicas to 1 or the value set in
// the minimum replicas metadata
func (f *FunctionScaler) Scale(functionName, namespace string) FunctionScaleResult {
start := time.Now()
if cachedResponse, hit := f.Cache.Get(functionName, namespace); hit &&
cachedResponse.AvailableReplicas > 0 {
return FunctionScaleResult{
Error: nil,
Available: true,
Found: true,
Duration: time.Since(start),
}
}
getKey := fmt.Sprintf("GetReplicas-%s.%s", functionName, namespace)
res, err, _ := f.SingleFlight.Do(getKey, func() (interface{}, error) {
return f.Config.ServiceQuery.GetReplicas(functionName, namespace)
})
if err != nil {
return FunctionScaleResult{
Error: err,
Available: false,
Found: false,
Duration: time.Since(start),
}
}
if res == nil {
return FunctionScaleResult{
Error: fmt.Errorf("empty response from server"),
Available: false,
Found: false,
Duration: time.Since(start),
}
}
queryResponse := res.(ServiceQueryResponse)
f.Cache.Set(functionName, namespace, queryResponse)
if queryResponse.AvailableReplicas == 0 {
minReplicas := uint64(1)
if queryResponse.MinReplicas > 0 {
minReplicas = queryResponse.MinReplicas
}
scaleResult := backoff(func(attempt int) error {
res, err, _ := f.SingleFlight.Do(getKey, func() (interface{}, error) {
return f.Config.ServiceQuery.GetReplicas(functionName, namespace)
})
if err != nil {
return err
}
queryResponse = res.(ServiceQueryResponse)
f.Cache.Set(functionName, namespace, queryResponse)
if queryResponse.Replicas > 0 {
return nil
}
setKey := fmt.Sprintf("SetReplicas-%s.%s", functionName, namespace)
if _, err, _ := f.SingleFlight.Do(setKey, func() (interface{}, error) {
log.Printf("[Scale %d] function=%s 0 => %d requested", attempt, functionName, minReplicas)
if err := f.Config.ServiceQuery.SetReplicas(functionName, namespace, minReplicas); err != nil {
return nil, fmt.Errorf("unable to scale function [%s], err: %s", functionName, err)
}
return nil, nil
}); err != nil {
return err
}
return nil
}, int(f.Config.SetScaleRetries), f.Config.FunctionPollInterval)
if scaleResult != nil {
return FunctionScaleResult{
Error: scaleResult,
Available: false,
Found: true,
Duration: time.Since(start),
}
}
for i := 0; i < int(f.Config.MaxPollCount); i++ {
res, err, _ := f.SingleFlight.Do(getKey, func() (interface{}, error) {
return f.Config.ServiceQuery.GetReplicas(functionName, namespace)
})
queryResponse := res.(ServiceQueryResponse)
if err == nil {
f.Cache.Set(functionName, namespace, queryResponse)
}
totalTime := time.Since(start)
if err != nil {
return FunctionScaleResult{
Error: err,
Available: false,
Found: true,
Duration: totalTime,
}
}
if queryResponse.AvailableReplicas > 0 {
log.Printf("[Scale] function=%s 0 => %d successful - %fs",
functionName, queryResponse.AvailableReplicas, totalTime.Seconds())
return FunctionScaleResult{
Error: nil,
Available: true,
Found: true,
Duration: totalTime,
}
}
time.Sleep(f.Config.FunctionPollInterval)
}
}
return FunctionScaleResult{
Error: nil,
Available: true,
Found: true,
Duration: time.Since(start),
}
}
type routine func(attempt int) error
func backoff(r routine, attempts int, interval time.Duration) error {
var err error
for i := 0; i < attempts; i++ {
res := r(i)
if res != nil {
err = res
log.Printf("Attempt: %d, had error: %s\n", i, res)
} else {
err = nil
break
}
time.Sleep(interval)
}
return err
}