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Move to single-flight for back-end queries

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When querying for replicas during a scale up event, then the
gateway can overwhelm the provider with requests. This is
especially true under high concurrent load.

The changes in this PR limit the inflight requests.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alex@openfaas.com>
This commit is contained in:
Alex Ellis (OpenFaaS Ltd)
2022-06-22 17:48:33 +01:00
committed by Alex Ellis
parent 8f8a93d43f
commit 6ed0ab71fb
3 changed files with 138 additions and 15 deletions
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23
gateway/scaling/function_query.go
View File

@ -3,12 +3,16 @@
package scaling
import "fmt"
import (
"fmt"
"log"
)
type CachedFunctionQuery struct {
cache FunctionCacher
serviceQuery ServiceQuery
emptyAnnotations map[string]string
singleFlight *SingleFlight
}
func NewCachedFunctionQuery(cache FunctionCacher, serviceQuery ServiceQuery) FunctionQuery {
@ -16,6 +20,7 @@ func NewCachedFunctionQuery(cache FunctionCacher, serviceQuery ServiceQuery) Fun
cache: cache,
serviceQuery: serviceQuery,
emptyAnnotations: map[string]string{},
singleFlight: NewSingleFlight(),
}
}
@ -35,13 +40,23 @@ func (c *CachedFunctionQuery) Get(fn string, ns string) (ServiceQueryResponse, e
query, hit := c.cache.Get(fn, ns)
if !hit {
key := fmt.Sprintf("GetReplicas-%s.%s", fn, ns)
queryResponse, err := c.singleFlight.Do(key, func() (interface{}, error) {
log.Printf("Cache miss - run GetReplicas")
// If there is a cache miss, then fetch the value from the provider API
return c.serviceQuery.GetReplicas(fn, ns)
})
log.Printf("Result: %v %v", queryResponse, err)
// If there is a cache miss, then fetch the value from the provider API
queryResponse, err := c.serviceQuery.GetReplicas(fn, ns)
if err != nil {
return ServiceQueryResponse{}, err
}
c.cache.Set(fn, ns, queryResponse)
if queryResponse != nil {
c.cache.Set(fn, ns, queryResponse.(ServiceQueryResponse))
}
} else {
return query, nil
}